From 6fba89813ccf333d2bc4d5caea04cd5f3c39eb50 Mon Sep 17 00:00:00 2001 From: Casey Schaufler Date: Wed, 23 Oct 2024 14:21:54 -0700 Subject: lsm: ensure the correct LSM context releaser Add a new lsm_context data structure to hold all the information about a "security context", including the string, its size and which LSM allocated the string. The allocation information is necessary because LSMs have different policies regarding the lifecycle of these strings. SELinux allocates and destroys them on each use, whereas Smack provides a pointer to an entry in a list that never goes away. Update security_release_secctx() to use the lsm_context instead of a (char *, len) pair. Change its callers to do likewise. The LSMs supporting this hook have had comments added to remind the developer that there is more work to be done. The BPF security module provides all LSM hooks. While there has yet to be a known instance of a BPF configuration that uses security contexts, the possibility is real. In the existing implementation there is potential for multiple frees in that case. Cc: linux-integrity@vger.kernel.org Cc: netdev@vger.kernel.org Cc: audit@vger.kernel.org Cc: netfilter-devel@vger.kernel.org To: Pablo Neira Ayuso Cc: linux-nfs@vger.kernel.org Cc: Todd Kjos Signed-off-by: Casey Schaufler [PM: subject tweak] Signed-off-by: Paul Moore --- security/security.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'security/security.c') diff --git a/security/security.c b/security/security.c index 09664e09fec9..b7f8ec93f6f0 100644 --- a/security/security.c +++ b/security/security.c @@ -4360,14 +4360,14 @@ EXPORT_SYMBOL(security_secctx_to_secid); /** * security_release_secctx() - Free a secctx buffer - * @secdata: secctx - * @seclen: length of secctx + * @cp: the security context * * Release the security context. */ -void security_release_secctx(char *secdata, u32 seclen) +void security_release_secctx(struct lsm_context *cp) { - call_void_hook(release_secctx, secdata, seclen); + call_void_hook(release_secctx, cp); + memset(cp, 0, sizeof(*cp)); } EXPORT_SYMBOL(security_release_secctx); -- cgit v1.2.3 From 2d470c778120d3cdb8d8ab250329ca85f49f12b1 Mon Sep 17 00:00:00 2001 From: Casey Schaufler Date: Wed, 23 Oct 2024 14:21:55 -0700 Subject: lsm: replace context+len with lsm_context Replace the (secctx,seclen) pointer pair with a single lsm_context pointer to allow return of the LSM identifier along with the context and context length. This allows security_release_secctx() to know how to release the context. Callers have been modified to use or save the returned data from the new structure. security_secid_to_secctx() and security_lsmproc_to_secctx() will now return the length value on success instead of 0. Cc: netdev@vger.kernel.org Cc: audit@vger.kernel.org Cc: netfilter-devel@vger.kernel.org Cc: Todd Kjos Signed-off-by: Casey Schaufler [PM: subject tweak, kdoc fix, signedness fix from Dan Carpenter] Signed-off-by: Paul Moore --- drivers/android/binder.c | 5 ++-- include/linux/lsm_hook_defs.h | 5 ++-- include/linux/security.h | 9 +++---- include/net/scm.h | 5 ++-- kernel/audit.c | 9 +++---- kernel/auditsc.c | 16 +++++------- net/ipv4/ip_sockglue.c | 4 +-- net/netfilter/nf_conntrack_netlink.c | 12 ++++----- net/netfilter/nf_conntrack_standalone.c | 4 +-- net/netfilter/nfnetlink_queue.c | 27 ++++++++------------ net/netlabel/netlabel_unlabeled.c | 14 ++++------ net/netlabel/netlabel_user.c | 3 +-- security/apparmor/include/secid.h | 5 ++-- security/apparmor/secid.c | 26 +++++++++---------- security/security.c | 34 +++++++++++-------------- security/selinux/hooks.c | 23 +++++++++++++---- security/smack/smack_lsm.c | 45 +++++++++++++++++++-------------- 17 files changed, 121 insertions(+), 125 deletions(-) (limited to 'security/security.c') diff --git a/drivers/android/binder.c b/drivers/android/binder.c index e8245df63289..919da8e674f5 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -3296,9 +3296,8 @@ static void binder_transaction(struct binder_proc *proc, size_t added_size; security_cred_getsecid(proc->cred, &secid); - ret = security_secid_to_secctx(secid, &lsmctx.context, - &lsmctx.len); - if (ret) { + ret = security_secid_to_secctx(secid, &lsmctx); + if (ret < 0) { binder_txn_error("%d:%d failed to get security context\n", thread->pid, proc->pid); return_error = BR_FAILED_REPLY; diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index c13df23132eb..01e5a8e09bba 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -295,10 +295,9 @@ LSM_HOOK(int, -EINVAL, getprocattr, struct task_struct *p, const char *name, char **value) LSM_HOOK(int, -EINVAL, setprocattr, const char *name, void *value, size_t size) LSM_HOOK(int, 0, ismaclabel, const char *name) -LSM_HOOK(int, -EOPNOTSUPP, secid_to_secctx, u32 secid, char **secdata, - u32 *seclen) +LSM_HOOK(int, -EOPNOTSUPP, secid_to_secctx, u32 secid, struct lsm_context *cp) LSM_HOOK(int, -EOPNOTSUPP, lsmprop_to_secctx, struct lsm_prop *prop, - char **secdata, u32 *seclen) + struct lsm_context *cp) LSM_HOOK(int, 0, secctx_to_secid, const char *secdata, u32 seclen, u32 *secid) LSM_HOOK(void, LSM_RET_VOID, release_secctx, struct lsm_context *cp) LSM_HOOK(void, LSM_RET_VOID, inode_invalidate_secctx, struct inode *inode) diff --git a/include/linux/security.h b/include/linux/security.h index 68e56935716b..58518bbc00a6 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -584,8 +584,8 @@ int security_getprocattr(struct task_struct *p, int lsmid, const char *name, int security_setprocattr(int lsmid, const char *name, void *value, size_t size); int security_netlink_send(struct sock *sk, struct sk_buff *skb); int security_ismaclabel(const char *name); -int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen); -int security_lsmprop_to_secctx(struct lsm_prop *prop, char **secdata, u32 *seclen); +int security_secid_to_secctx(u32 secid, struct lsm_context *cp); +int security_lsmprop_to_secctx(struct lsm_prop *prop, struct lsm_context *cp); int security_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid); void security_release_secctx(struct lsm_context *cp); void security_inode_invalidate_secctx(struct inode *inode); @@ -1557,14 +1557,13 @@ static inline int security_ismaclabel(const char *name) return 0; } -static inline int security_secid_to_secctx(u32 secid, char **secdata, - u32 *seclen) +static inline int security_secid_to_secctx(u32 secid, struct lsm_context *cp) { return -EOPNOTSUPP; } static inline int security_lsmprop_to_secctx(struct lsm_prop *prop, - char **secdata, u32 *seclen) + struct lsm_context *cp) { return -EOPNOTSUPP; } diff --git a/include/net/scm.h b/include/net/scm.h index f75449e1d876..22bb49589fde 100644 --- a/include/net/scm.h +++ b/include/net/scm.h @@ -109,10 +109,9 @@ static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct sc int err; if (test_bit(SOCK_PASSSEC, &sock->flags)) { - err = security_secid_to_secctx(scm->secid, &ctx.context, - &ctx.len); + err = security_secid_to_secctx(scm->secid, &ctx); - if (!err) { + if (err >= 0) { put_cmsg(msg, SOL_SOCKET, SCM_SECURITY, ctx.len, ctx.context); security_release_secctx(&ctx); diff --git a/kernel/audit.c b/kernel/audit.c index 1d48d0654a46..13d0144efaa3 100644 --- a/kernel/audit.c +++ b/kernel/audit.c @@ -1473,9 +1473,8 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh, case AUDIT_SIGNAL_INFO: if (lsmprop_is_set(&audit_sig_lsm)) { err = security_lsmprop_to_secctx(&audit_sig_lsm, - &lsmctx.context, - &lsmctx.len); - if (err) + &lsmctx); + if (err < 0) return err; } sig_data = kmalloc(struct_size(sig_data, ctx, lsmctx.len), @@ -2188,8 +2187,8 @@ int audit_log_task_context(struct audit_buffer *ab) if (!lsmprop_is_set(&prop)) return 0; - error = security_lsmprop_to_secctx(&prop, &ctx.context, &ctx.len); - if (error) { + error = security_lsmprop_to_secctx(&prop, &ctx); + if (error < 0) { if (error != -EINVAL) goto error_path; return 0; diff --git a/kernel/auditsc.c b/kernel/auditsc.c index de8fac6c5bd3..bb0e7346d916 100644 --- a/kernel/auditsc.c +++ b/kernel/auditsc.c @@ -1109,7 +1109,7 @@ static int audit_log_pid_context(struct audit_context *context, pid_t pid, from_kuid(&init_user_ns, auid), from_kuid(&init_user_ns, uid), sessionid); if (lsmprop_is_set(prop)) { - if (security_lsmprop_to_secctx(prop, &ctx.context, &ctx.len)) { + if (security_lsmprop_to_secctx(prop, &ctx) < 0) { audit_log_format(ab, " obj=(none)"); rc = 1; } else { @@ -1370,7 +1370,6 @@ static void audit_log_time(struct audit_context *context, struct audit_buffer ** static void show_special(struct audit_context *context, int *call_panic) { - struct lsm_context lsmcxt; struct audit_buffer *ab; int i; @@ -1393,16 +1392,14 @@ static void show_special(struct audit_context *context, int *call_panic) from_kgid(&init_user_ns, context->ipc.gid), context->ipc.mode); if (lsmprop_is_set(&context->ipc.oprop)) { - char *ctx = NULL; - u32 len; + struct lsm_context lsmctx; if (security_lsmprop_to_secctx(&context->ipc.oprop, - &ctx, &len)) { + &lsmctx) < 0) { *call_panic = 1; } else { - audit_log_format(ab, " obj=%s", ctx); - lsmcontext_init(&lsmcxt, ctx, len, 0); - security_release_secctx(&lsmcxt); + audit_log_format(ab, " obj=%s", lsmctx.context); + security_release_secctx(&lsmctx); } } if (context->ipc.has_perm) { @@ -1563,8 +1560,7 @@ static void audit_log_name(struct audit_context *context, struct audit_names *n, if (lsmprop_is_set(&n->oprop)) { struct lsm_context ctx; - if (security_lsmprop_to_secctx(&n->oprop, &ctx.context, - &ctx.len)) { + if (security_lsmprop_to_secctx(&n->oprop, &ctx) < 0) { if (call_panic) *call_panic = 2; } else { diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c index a8180dcc2a32..dadbf619b20f 100644 --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -136,8 +136,8 @@ static void ip_cmsg_recv_security(struct msghdr *msg, struct sk_buff *skb) if (err) return; - err = security_secid_to_secctx(secid, &ctx.context, &ctx.len); - if (err) + err = security_secid_to_secctx(secid, &ctx); + if (err < 0) return; put_cmsg(msg, SOL_IP, SCM_SECURITY, ctx.len, ctx.context); diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c index 22f46be33f1e..7b74b24348fc 100644 --- a/net/netfilter/nf_conntrack_netlink.c +++ b/net/netfilter/nf_conntrack_netlink.c @@ -360,8 +360,8 @@ static int ctnetlink_dump_secctx(struct sk_buff *skb, const struct nf_conn *ct) struct lsm_context ctx; int ret; - ret = security_secid_to_secctx(ct->secmark, &ctx.context, &ctx.len); - if (ret) + ret = security_secid_to_secctx(ct->secmark, &ctx); + if (ret < 0) return 0; ret = -1; @@ -663,14 +663,14 @@ static inline size_t ctnetlink_acct_size(const struct nf_conn *ct) static inline int ctnetlink_secctx_size(const struct nf_conn *ct) { #ifdef CONFIG_NF_CONNTRACK_SECMARK - int len, ret; + int ret; - ret = security_secid_to_secctx(ct->secmark, NULL, &len); - if (ret) + ret = security_secid_to_secctx(ct->secmark, NULL); + if (ret < 0) return 0; return nla_total_size(0) /* CTA_SECCTX */ - + nla_total_size(sizeof(char) * len); /* CTA_SECCTX_NAME */ + + nla_total_size(sizeof(char) * ret); /* CTA_SECCTX_NAME */ #else return 0; #endif diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c index 5f7fd23b7afe..502cf10aab41 100644 --- a/net/netfilter/nf_conntrack_standalone.c +++ b/net/netfilter/nf_conntrack_standalone.c @@ -175,8 +175,8 @@ static void ct_show_secctx(struct seq_file *s, const struct nf_conn *ct) struct lsm_context ctx; int ret; - ret = security_secid_to_secctx(ct->secmark, &ctx.context, &ctx.len); - if (ret) + ret = security_secid_to_secctx(ct->secmark, &ctx); + if (ret < 0) return; seq_printf(s, "secctx=%s ", ctx.context); diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c index 37757cd77cf1..5110f29b2f40 100644 --- a/net/netfilter/nfnetlink_queue.c +++ b/net/netfilter/nfnetlink_queue.c @@ -470,18 +470,18 @@ static int nfqnl_put_sk_classid(struct sk_buff *skb, struct sock *sk) return 0; } -static u32 nfqnl_get_sk_secctx(struct sk_buff *skb, char **secdata) +static u32 nfqnl_get_sk_secctx(struct sk_buff *skb, struct lsm_context *ctx) { u32 seclen = 0; #if IS_ENABLED(CONFIG_NETWORK_SECMARK) + if (!skb || !sk_fullsock(skb->sk)) return 0; read_lock_bh(&skb->sk->sk_callback_lock); if (skb->secmark) - security_secid_to_secctx(skb->secmark, secdata, &seclen); - + seclen = security_secid_to_secctx(skb->secmark, ctx); read_unlock_bh(&skb->sk->sk_callback_lock); #endif return seclen; @@ -567,8 +567,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue, enum ip_conntrack_info ctinfo = 0; const struct nfnl_ct_hook *nfnl_ct; bool csum_verify; - struct lsm_context scaff; /* scaffolding */ - char *secdata = NULL; + struct lsm_context ctx; u32 seclen = 0; ktime_t tstamp; @@ -643,8 +642,8 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue, } if ((queue->flags & NFQA_CFG_F_SECCTX) && entskb->sk) { - seclen = nfqnl_get_sk_secctx(entskb, &secdata); - if (seclen) + seclen = nfqnl_get_sk_secctx(entskb, &ctx); + if (seclen >= 0) size += nla_total_size(seclen); } @@ -783,7 +782,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue, if (nfqnl_put_sk_classid(skb, entskb->sk) < 0) goto nla_put_failure; - if (seclen && nla_put(skb, NFQA_SECCTX, seclen, secdata)) + if (seclen && nla_put(skb, NFQA_SECCTX, ctx.len, ctx.context)) goto nla_put_failure; if (ct && nfnl_ct->build(skb, ct, ctinfo, NFQA_CT, NFQA_CT_INFO) < 0) @@ -811,10 +810,8 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue, } nlh->nlmsg_len = skb->len; - if (seclen) { - lsmcontext_init(&scaff, secdata, seclen, 0); - security_release_secctx(&scaff); - } + if (seclen >= 0) + security_release_secctx(&ctx); return skb; nla_put_failure: @@ -822,10 +819,8 @@ nla_put_failure: kfree_skb(skb); net_err_ratelimited("nf_queue: error creating packet message\n"); nlmsg_failure: - if (seclen) { - lsmcontext_init(&scaff, secdata, seclen, 0); - security_release_secctx(&scaff); - } + if (seclen >= 0) + security_release_secctx(&ctx); return NULL; } diff --git a/net/netlabel/netlabel_unlabeled.c b/net/netlabel/netlabel_unlabeled.c index 921fa8eeb451..bd7094f225d1 100644 --- a/net/netlabel/netlabel_unlabeled.c +++ b/net/netlabel/netlabel_unlabeled.c @@ -437,9 +437,7 @@ int netlbl_unlhsh_add(struct net *net, unlhsh_add_return: rcu_read_unlock(); if (audit_buf != NULL) { - if (security_secid_to_secctx(secid, - &ctx.context, - &ctx.len) == 0) { + if (security_secid_to_secctx(secid, &ctx) == 0) { audit_log_format(audit_buf, " sec_obj=%s", ctx.context); security_release_secctx(&ctx); } @@ -492,8 +490,7 @@ static int netlbl_unlhsh_remove_addr4(struct net *net, addr->s_addr, mask->s_addr); dev_put(dev); if (entry != NULL && - security_secid_to_secctx(entry->secid, - &ctx.context, &ctx.len) == 0) { + security_secid_to_secctx(entry->secid, &ctx) == 0) { audit_log_format(audit_buf, " sec_obj=%s", ctx.context); security_release_secctx(&ctx); } @@ -551,8 +548,7 @@ static int netlbl_unlhsh_remove_addr6(struct net *net, addr, mask); dev_put(dev); if (entry != NULL && - security_secid_to_secctx(entry->secid, - &ctx.context, &ctx.len) == 0) { + security_secid_to_secctx(entry->secid, &ctx) == 0) { audit_log_format(audit_buf, " sec_obj=%s", ctx.context); security_release_secctx(&ctx); } @@ -1123,8 +1119,8 @@ static int netlbl_unlabel_staticlist_gen(u32 cmd, secid = addr6->secid; } - ret_val = security_secid_to_secctx(secid, &ctx.context, &ctx.len); - if (ret_val != 0) + ret_val = security_secid_to_secctx(secid, &ctx); + if (ret_val < 0) goto list_cb_failure; ret_val = nla_put(cb_arg->skb, NLBL_UNLABEL_A_SECCTX, diff --git a/net/netlabel/netlabel_user.c b/net/netlabel/netlabel_user.c index f5e7a9919df1..0d04d23aafe7 100644 --- a/net/netlabel/netlabel_user.c +++ b/net/netlabel/netlabel_user.c @@ -98,8 +98,7 @@ struct audit_buffer *netlbl_audit_start_common(int type, audit_info->sessionid); if (lsmprop_is_set(&audit_info->prop) && - security_lsmprop_to_secctx(&audit_info->prop, &ctx.context, - &ctx.len) == 0) { + security_lsmprop_to_secctx(&audit_info->prop, &ctx) > 0) { audit_log_format(audit_buf, " subj=%s", ctx.context); security_release_secctx(&ctx); } diff --git a/security/apparmor/include/secid.h b/security/apparmor/include/secid.h index 1bcde2f45f24..6025d3849cf8 100644 --- a/security/apparmor/include/secid.h +++ b/security/apparmor/include/secid.h @@ -25,9 +25,8 @@ struct aa_label; extern int apparmor_display_secid_mode; struct aa_label *aa_secid_to_label(u32 secid); -int apparmor_secid_to_secctx(u32 secid, char **secdata, u32 *seclen); -int apparmor_lsmprop_to_secctx(struct lsm_prop *prop, char **secdata, - u32 *seclen); +int apparmor_secid_to_secctx(u32 secid, struct lsm_context *cp); +int apparmor_lsmprop_to_secctx(struct lsm_prop *prop, struct lsm_context *cp); int apparmor_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid); void apparmor_release_secctx(struct lsm_context *cp); diff --git a/security/apparmor/secid.c b/security/apparmor/secid.c index 43e4dab7f6e6..b08969ec34b7 100644 --- a/security/apparmor/secid.c +++ b/security/apparmor/secid.c @@ -47,23 +47,21 @@ struct aa_label *aa_secid_to_label(u32 secid) return xa_load(&aa_secids, secid); } -static int apparmor_label_to_secctx(struct aa_label *label, char **secdata, - u32 *seclen) +static int apparmor_label_to_secctx(struct aa_label *label, + struct lsm_context *cp) { /* TODO: cache secctx and ref count so we don't have to recreate */ int flags = FLAG_VIEW_SUBNS | FLAG_HIDDEN_UNCONFINED | FLAG_ABS_ROOT; int len; - AA_BUG(!seclen); - if (!label) return -EINVAL; if (apparmor_display_secid_mode) flags |= FLAG_SHOW_MODE; - if (secdata) - len = aa_label_asxprint(secdata, root_ns, label, + if (cp) + len = aa_label_asxprint(&cp->context, root_ns, label, flags, GFP_ATOMIC); else len = aa_label_snxprint(NULL, 0, root_ns, label, flags); @@ -71,26 +69,28 @@ static int apparmor_label_to_secctx(struct aa_label *label, char **secdata, if (len < 0) return -ENOMEM; - *seclen = len; + if (cp) { + cp->len = len; + cp->id = LSM_ID_APPARMOR; + } - return 0; + return len; } -int apparmor_secid_to_secctx(u32 secid, char **secdata, u32 *seclen) +int apparmor_secid_to_secctx(u32 secid, struct lsm_context *cp) { struct aa_label *label = aa_secid_to_label(secid); - return apparmor_label_to_secctx(label, secdata, seclen); + return apparmor_label_to_secctx(label, cp); } -int apparmor_lsmprop_to_secctx(struct lsm_prop *prop, char **secdata, - u32 *seclen) +int apparmor_lsmprop_to_secctx(struct lsm_prop *prop, struct lsm_context *cp) { struct aa_label *label; label = prop->apparmor.label; - return apparmor_label_to_secctx(label, secdata, seclen); + return apparmor_label_to_secctx(label, cp); } int apparmor_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid) diff --git a/security/security.c b/security/security.c index b7f8ec93f6f0..1edf8fb2046c 100644 --- a/security/security.c +++ b/security/security.c @@ -4304,40 +4304,36 @@ EXPORT_SYMBOL(security_ismaclabel); /** * security_secid_to_secctx() - Convert a secid to a secctx * @secid: secid - * @secdata: secctx - * @seclen: secctx length + * @cp: the LSM context * - * Convert secid to security context. If @secdata is NULL the length of the - * result will be returned in @seclen, but no @secdata will be returned. This + * Convert secid to security context. If @cp is NULL the length of the + * result will be returned, but no data will be returned. This * does mean that the length could change between calls to check the length and - * the next call which actually allocates and returns the @secdata. + * the next call which actually allocates and returns the data. * - * Return: Return 0 on success, error on failure. + * Return: Return length of data on success, error on failure. */ -int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen) +int security_secid_to_secctx(u32 secid, struct lsm_context *cp) { - return call_int_hook(secid_to_secctx, secid, secdata, seclen); + return call_int_hook(secid_to_secctx, secid, cp); } EXPORT_SYMBOL(security_secid_to_secctx); /** * security_lsmprop_to_secctx() - Convert a lsm_prop to a secctx * @prop: lsm specific information - * @secdata: secctx - * @seclen: secctx length + * @cp: the LSM context * - * Convert a @prop entry to security context. If @secdata is NULL the - * length of the result will be returned in @seclen, but no @secdata - * will be returned. This does mean that the length could change between - * calls to check the length and the next call which actually allocates - * and returns the @secdata. + * Convert a @prop entry to security context. If @cp is NULL the + * length of the result will be returned. This does mean that the + * length could change between calls to check the length and the + * next call which actually allocates and returns the @cp. * - * Return: Return 0 on success, error on failure. + * Return: Return length of data on success, error on failure. */ -int security_lsmprop_to_secctx(struct lsm_prop *prop, char **secdata, - u32 *seclen) +int security_lsmprop_to_secctx(struct lsm_prop *prop, struct lsm_context *cp) { - return call_int_hook(lsmprop_to_secctx, prop, secdata, seclen); + return call_int_hook(lsmprop_to_secctx, prop, cp); } EXPORT_SYMBOL(security_lsmprop_to_secctx); diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index aabc724f4d44..ddc24db7c0b2 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -6640,15 +6640,28 @@ static int selinux_ismaclabel(const char *name) return (strcmp(name, XATTR_SELINUX_SUFFIX) == 0); } -static int selinux_secid_to_secctx(u32 secid, char **secdata, u32 *seclen) +static int selinux_secid_to_secctx(u32 secid, struct lsm_context *cp) { - return security_sid_to_context(secid, secdata, seclen); + u32 seclen; + int ret; + + if (cp) { + cp->id = LSM_ID_SELINUX; + ret = security_sid_to_context(secid, &cp->context, &cp->len); + if (ret < 0) + return ret; + return cp->len; + } + ret = security_sid_to_context(secid, NULL, &seclen); + if (ret < 0) + return ret; + return seclen; } -static int selinux_lsmprop_to_secctx(struct lsm_prop *prop, char **secdata, - u32 *seclen) +static int selinux_lsmprop_to_secctx(struct lsm_prop *prop, + struct lsm_context *cp) { - return selinux_secid_to_secctx(prop->selinux.secid, secdata, seclen); + return selinux_secid_to_secctx(prop->selinux.secid, cp); } static int selinux_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid) diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index 0c476282e279..4084f99c493c 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -4817,41 +4817,48 @@ static int smack_ismaclabel(const char *name) return (strcmp(name, XATTR_SMACK_SUFFIX) == 0); } +/** + * smack_to_secctx - fill a lsm_context + * @skp: Smack label + * @cp: destination + * + * Fill the passed @cp and return the length of the string + */ +static int smack_to_secctx(struct smack_known *skp, struct lsm_context *cp) +{ + int len = strlen(skp->smk_known); + + if (cp) { + cp->context = skp->smk_known; + cp->len = len; + cp->id = LSM_ID_SMACK; + } + return len; +} + /** * smack_secid_to_secctx - return the smack label for a secid * @secid: incoming integer - * @secdata: destination - * @seclen: how long it is + * @cp: destination * * Exists for networking code. */ -static int smack_secid_to_secctx(u32 secid, char **secdata, u32 *seclen) +static int smack_secid_to_secctx(u32 secid, struct lsm_context *cp) { - struct smack_known *skp = smack_from_secid(secid); - - if (secdata) - *secdata = skp->smk_known; - *seclen = strlen(skp->smk_known); - return 0; + return smack_to_secctx(smack_from_secid(secid), cp); } /** * smack_lsmprop_to_secctx - return the smack label * @prop: includes incoming Smack data - * @secdata: destination - * @seclen: how long it is + * @cp: destination * * Exists for audit code. */ -static int smack_lsmprop_to_secctx(struct lsm_prop *prop, char **secdata, - u32 *seclen) +static int smack_lsmprop_to_secctx(struct lsm_prop *prop, + struct lsm_context *cp) { - struct smack_known *skp = prop->smack.skp; - - if (secdata) - *secdata = skp->smk_known; - *seclen = strlen(skp->smk_known); - return 0; + return smack_to_secctx(prop->smack.skp, cp); } /** -- cgit v1.2.3 From 76ecf306ae5da84ef8f48c7a2608736e6866440c Mon Sep 17 00:00:00 2001 From: Casey Schaufler Date: Wed, 23 Oct 2024 14:21:56 -0700 Subject: lsm: use lsm_context in security_inode_getsecctx Change the security_inode_getsecctx() interface to fill a lsm_context structure instead of data and length pointers. This provides the information about which LSM created the context so that security_release_secctx() can use the correct hook. Cc: linux-nfs@vger.kernel.org Signed-off-by: Casey Schaufler [PM: subject tweak] Signed-off-by: Paul Moore --- fs/nfsd/nfs4xdr.c | 26 ++++++++++---------------- include/linux/lsm_hook_defs.h | 4 ++-- include/linux/security.h | 5 +++-- security/security.c | 12 ++++++------ security/selinux/hooks.c | 10 ++++++---- security/smack/smack_lsm.c | 7 ++++--- 6 files changed, 31 insertions(+), 33 deletions(-) (limited to 'security/security.c') diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c index 95ec6a4b4da3..8dd2e2ada474 100644 --- a/fs/nfsd/nfs4xdr.c +++ b/fs/nfsd/nfs4xdr.c @@ -2818,11 +2818,11 @@ static __be32 nfsd4_encode_nfsace4(struct xdr_stream *xdr, struct svc_rqst *rqst #ifdef CONFIG_NFSD_V4_SECURITY_LABEL static inline __be32 nfsd4_encode_security_label(struct xdr_stream *xdr, struct svc_rqst *rqstp, - void *context, int len) + const struct lsm_context *context) { __be32 *p; - p = xdr_reserve_space(xdr, len + 4 + 4 + 4); + p = xdr_reserve_space(xdr, context->len + 4 + 4 + 4); if (!p) return nfserr_resource; @@ -2832,13 +2832,13 @@ nfsd4_encode_security_label(struct xdr_stream *xdr, struct svc_rqst *rqstp, */ *p++ = cpu_to_be32(0); /* lfs */ *p++ = cpu_to_be32(0); /* pi */ - p = xdr_encode_opaque(p, context, len); + p = xdr_encode_opaque(p, context->context, context->len); return 0; } #else static inline __be32 nfsd4_encode_security_label(struct xdr_stream *xdr, struct svc_rqst *rqstp, - void *context, int len) + struct lsm_context *context) { return 0; } #endif @@ -2920,8 +2920,7 @@ struct nfsd4_fattr_args { struct kstatfs statfs; struct nfs4_acl *acl; #ifdef CONFIG_NFSD_V4_SECURITY_LABEL - void *context; - int contextlen; + struct lsm_context context; #endif u32 rdattr_err; bool contextsupport; @@ -3376,8 +3375,7 @@ static __be32 nfsd4_encode_fattr4_suppattr_exclcreat(struct xdr_stream *xdr, static __be32 nfsd4_encode_fattr4_sec_label(struct xdr_stream *xdr, const struct nfsd4_fattr_args *args) { - return nfsd4_encode_security_label(xdr, args->rqstp, - args->context, args->contextlen); + return nfsd4_encode_security_label(xdr, args->rqstp, &args->context); } #endif @@ -3527,7 +3525,7 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr, args.ignore_crossmnt = (ignore_crossmnt != 0); args.acl = NULL; #ifdef CONFIG_NFSD_V4_SECURITY_LABEL - args.context = NULL; + args.context.context = NULL; #endif /* @@ -3607,7 +3605,7 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr, attrmask[0] & FATTR4_WORD0_SUPPORTED_ATTRS) { if (exp->ex_flags & NFSEXP_SECURITY_LABEL) err = security_inode_getsecctx(d_inode(dentry), - &args.context, &args.contextlen); + &args.context); else err = -EOPNOTSUPP; args.contextsupport = (err == 0); @@ -3644,12 +3642,8 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr, out: #ifdef CONFIG_NFSD_V4_SECURITY_LABEL - if (args.context) { - struct lsm_context scaff; /* scaffolding */ - - lsmcontext_init(&scaff, args.context, args.contextlen, 0); - security_release_secctx(&scaff); - } + if (args.context.context) + security_release_secctx(&args.context); #endif /* CONFIG_NFSD_V4_SECURITY_LABEL */ kfree(args.acl); if (tempfh) { diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index 01e5a8e09bba..69e1076448c6 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -303,8 +303,8 @@ LSM_HOOK(void, LSM_RET_VOID, release_secctx, struct lsm_context *cp) LSM_HOOK(void, LSM_RET_VOID, inode_invalidate_secctx, struct inode *inode) LSM_HOOK(int, 0, inode_notifysecctx, struct inode *inode, void *ctx, u32 ctxlen) LSM_HOOK(int, 0, inode_setsecctx, struct dentry *dentry, void *ctx, u32 ctxlen) -LSM_HOOK(int, -EOPNOTSUPP, inode_getsecctx, struct inode *inode, void **ctx, - u32 *ctxlen) +LSM_HOOK(int, -EOPNOTSUPP, inode_getsecctx, struct inode *inode, + struct lsm_context *cp) #if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE) LSM_HOOK(int, 0, post_notification, const struct cred *w_cred, diff --git a/include/linux/security.h b/include/linux/security.h index 58518bbc00a6..29f8100bc7c8 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -591,7 +591,7 @@ void security_release_secctx(struct lsm_context *cp); void security_inode_invalidate_secctx(struct inode *inode); int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen); int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen); -int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen); +int security_inode_getsecctx(struct inode *inode, struct lsm_context *cp); int security_locked_down(enum lockdown_reason what); int lsm_fill_user_ctx(struct lsm_ctx __user *uctx, u32 *uctx_len, void *val, size_t val_len, u64 id, u64 flags); @@ -1591,7 +1591,8 @@ static inline int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 { return -EOPNOTSUPP; } -static inline int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen) +static inline int security_inode_getsecctx(struct inode *inode, + struct lsm_context *cp) { return -EOPNOTSUPP; } diff --git a/security/security.c b/security/security.c index 1edf8fb2046c..1aecf1696c50 100644 --- a/security/security.c +++ b/security/security.c @@ -4426,17 +4426,17 @@ EXPORT_SYMBOL(security_inode_setsecctx); /** * security_inode_getsecctx() - Get the security label of an inode * @inode: inode - * @ctx: secctx - * @ctxlen: length of secctx + * @cp: security context * - * On success, returns 0 and fills out @ctx and @ctxlen with the security - * context for the given @inode. + * On success, returns 0 and fills out @cp with the security context + * for the given @inode. * * Return: Returns 0 on success, error on failure. */ -int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen) +int security_inode_getsecctx(struct inode *inode, struct lsm_context *cp) { - return call_int_hook(inode_getsecctx, inode, ctx, ctxlen); + memset(cp, 0, sizeof(*cp)); + return call_int_hook(inode_getsecctx, inode, cp); } EXPORT_SYMBOL(security_inode_getsecctx); diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index ddc24db7c0b2..9254570de103 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -6711,14 +6711,16 @@ static int selinux_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen) ctx, ctxlen, 0, NULL); } -static int selinux_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen) +static int selinux_inode_getsecctx(struct inode *inode, struct lsm_context *cp) { - int len = 0; + int len; len = selinux_inode_getsecurity(&nop_mnt_idmap, inode, - XATTR_SELINUX_SUFFIX, ctx, true); + XATTR_SELINUX_SUFFIX, + (void **)&cp->context, true); if (len < 0) return len; - *ctxlen = len; + cp->len = len; + cp->id = LSM_ID_SELINUX; return 0; } #ifdef CONFIG_KEYS diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index 4084f99c493c..55a556f17ade 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -4898,12 +4898,13 @@ static int smack_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen) ctx, ctxlen, 0, NULL); } -static int smack_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen) +static int smack_inode_getsecctx(struct inode *inode, struct lsm_context *cp) { struct smack_known *skp = smk_of_inode(inode); - *ctx = skp->smk_known; - *ctxlen = strlen(skp->smk_known); + cp->context = skp->smk_known; + cp->len = strlen(skp->smk_known); + cp->id = LSM_ID_SMACK; return 0; } -- cgit v1.2.3 From b530104f50e86db6f187d39fed5821b3cca755ee Mon Sep 17 00:00:00 2001 From: Casey Schaufler Date: Wed, 23 Oct 2024 14:21:57 -0700 Subject: lsm: lsm_context in security_dentry_init_security Replace the (secctx,seclen) pointer pair with a single lsm_context pointer to allow return of the LSM identifier along with the context and context length. This allows security_release_secctx() to know how to release the context. Callers have been modified to use or save the returned data from the new structure. Cc: ceph-devel@vger.kernel.org Cc: linux-nfs@vger.kernel.org Signed-off-by: Casey Schaufler [PM: subject tweak] Signed-off-by: Paul Moore --- fs/ceph/super.h | 3 +-- fs/ceph/xattr.c | 16 ++++++---------- fs/fuse/dir.c | 35 ++++++++++++++++++----------------- fs/nfs/nfs4proc.c | 20 ++++++++++++-------- include/linux/lsm_hook_defs.h | 2 +- include/linux/security.h | 26 +++----------------------- security/security.c | 9 ++++----- security/selinux/hooks.c | 8 ++++---- 8 files changed, 49 insertions(+), 70 deletions(-) (limited to 'security/security.c') diff --git a/fs/ceph/super.h b/fs/ceph/super.h index af14ec382246..7fa1e7be50e4 100644 --- a/fs/ceph/super.h +++ b/fs/ceph/super.h @@ -1132,8 +1132,7 @@ struct ceph_acl_sec_ctx { void *acl; #endif #ifdef CONFIG_CEPH_FS_SECURITY_LABEL - void *sec_ctx; - u32 sec_ctxlen; + struct lsm_context lsmctx; #endif #ifdef CONFIG_FS_ENCRYPTION struct ceph_fscrypt_auth *fscrypt_auth; diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c index 2a14335a4bb7..537165db4519 100644 --- a/fs/ceph/xattr.c +++ b/fs/ceph/xattr.c @@ -1383,8 +1383,7 @@ int ceph_security_init_secctx(struct dentry *dentry, umode_t mode, int err; err = security_dentry_init_security(dentry, mode, &dentry->d_name, - &name, &as_ctx->sec_ctx, - &as_ctx->sec_ctxlen); + &name, &as_ctx->lsmctx); if (err < 0) { WARN_ON_ONCE(err != -EOPNOTSUPP); err = 0; /* do nothing */ @@ -1409,7 +1408,7 @@ int ceph_security_init_secctx(struct dentry *dentry, umode_t mode, */ name_len = strlen(name); err = ceph_pagelist_reserve(pagelist, - 4 * 2 + name_len + as_ctx->sec_ctxlen); + 4 * 2 + name_len + as_ctx->lsmctx.len); if (err) goto out; @@ -1432,8 +1431,9 @@ int ceph_security_init_secctx(struct dentry *dentry, umode_t mode, ceph_pagelist_encode_32(pagelist, name_len); ceph_pagelist_append(pagelist, name, name_len); - ceph_pagelist_encode_32(pagelist, as_ctx->sec_ctxlen); - ceph_pagelist_append(pagelist, as_ctx->sec_ctx, as_ctx->sec_ctxlen); + ceph_pagelist_encode_32(pagelist, as_ctx->lsmctx.len); + ceph_pagelist_append(pagelist, as_ctx->lsmctx.context, + as_ctx->lsmctx.len); err = 0; out: @@ -1446,16 +1446,12 @@ out: void ceph_release_acl_sec_ctx(struct ceph_acl_sec_ctx *as_ctx) { -#ifdef CONFIG_CEPH_FS_SECURITY_LABEL - struct lsm_context scaff; /* scaffolding */ -#endif #ifdef CONFIG_CEPH_FS_POSIX_ACL posix_acl_release(as_ctx->acl); posix_acl_release(as_ctx->default_acl); #endif #ifdef CONFIG_CEPH_FS_SECURITY_LABEL - lsmcontext_init(&scaff, as_ctx->sec_ctx, as_ctx->sec_ctxlen, 0); - security_release_secctx(&scaff); + security_release_secctx(&as_ctx->lsmctx); #endif #ifdef CONFIG_FS_ENCRYPTION kfree(as_ctx->fscrypt_auth); diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 494ac372ace0..0b2f8567ca30 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -467,29 +467,29 @@ static int get_security_context(struct dentry *entry, umode_t mode, { struct fuse_secctx *fctx; struct fuse_secctx_header *header; - void *ctx = NULL, *ptr; - u32 ctxlen, total_len = sizeof(*header); + struct lsm_context lsmctx = { }; + void *ptr; + u32 total_len = sizeof(*header); int err, nr_ctx = 0; - const char *name; + const char *name = NULL; size_t namelen; err = security_dentry_init_security(entry, mode, &entry->d_name, - &name, &ctx, &ctxlen); - if (err) { - if (err != -EOPNOTSUPP) - goto out_err; - /* No LSM is supporting this security hook. Ignore error */ - ctxlen = 0; - ctx = NULL; - } + &name, &lsmctx); + + /* If no LSM is supporting this security hook ignore error */ + if (err && err != -EOPNOTSUPP) + goto out_err; - if (ctxlen) { + if (lsmctx.len) { nr_ctx = 1; namelen = strlen(name) + 1; err = -EIO; - if (WARN_ON(namelen > XATTR_NAME_MAX + 1 || ctxlen > S32_MAX)) + if (WARN_ON(namelen > XATTR_NAME_MAX + 1 || + lsmctx.len > S32_MAX)) goto out_err; - total_len += FUSE_REC_ALIGN(sizeof(*fctx) + namelen + ctxlen); + total_len += FUSE_REC_ALIGN(sizeof(*fctx) + namelen + + lsmctx.len); } err = -ENOMEM; @@ -502,19 +502,20 @@ static int get_security_context(struct dentry *entry, umode_t mode, ptr += sizeof(*header); if (nr_ctx) { fctx = ptr; - fctx->size = ctxlen; + fctx->size = lsmctx.len; ptr += sizeof(*fctx); strcpy(ptr, name); ptr += namelen; - memcpy(ptr, ctx, ctxlen); + memcpy(ptr, lsmctx.context, lsmctx.len); } ext->size = total_len; ext->value = header; err = 0; out_err: - kfree(ctx); + if (nr_ctx) + security_release_secctx(&lsmctx); return err; } diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index 2daeb6f663d9..d615d520f8cf 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -114,6 +114,7 @@ static inline struct nfs4_label * nfs4_label_init_security(struct inode *dir, struct dentry *dentry, struct iattr *sattr, struct nfs4_label *label) { + struct lsm_context shim; int err; if (label == NULL) @@ -128,21 +129,24 @@ nfs4_label_init_security(struct inode *dir, struct dentry *dentry, label->label = NULL; err = security_dentry_init_security(dentry, sattr->ia_mode, - &dentry->d_name, NULL, - (void **)&label->label, &label->len); - if (err == 0) - return label; + &dentry->d_name, NULL, &shim); + if (err) + return NULL; - return NULL; + label->label = shim.context; + label->len = shim.len; + return label; } static inline void nfs4_label_release_security(struct nfs4_label *label) { - struct lsm_context scaff; /* scaffolding */ + struct lsm_context shim; if (label) { - lsmcontext_init(&scaff, label->label, label->len, 0); - security_release_secctx(&scaff); + shim.context = label->label; + shim.len = label->len; + shim.id = LSM_ID_UNDEF; + security_release_secctx(&shim); } } static inline u32 *nfs4_bitmask(struct nfs_server *server, struct nfs4_label *label) diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index 69e1076448c6..e2f1ce37c41e 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -83,7 +83,7 @@ LSM_HOOK(int, 0, move_mount, const struct path *from_path, const struct path *to_path) LSM_HOOK(int, -EOPNOTSUPP, dentry_init_security, struct dentry *dentry, int mode, const struct qstr *name, const char **xattr_name, - void **ctx, u32 *ctxlen) + struct lsm_context *cp) LSM_HOOK(int, 0, dentry_create_files_as, struct dentry *dentry, int mode, struct qstr *name, const struct cred *old, struct cred *new) diff --git a/include/linux/security.h b/include/linux/security.h index 29f8100bc7c8..980b6c207cad 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -237,25 +237,6 @@ struct lsm_context { int id; /* Identifies the module */ }; -/** - * lsmcontext_init - initialize an lsmcontext structure. - * @cp: Pointer to the context to initialize - * @context: Initial context, or NULL - * @size: Size of context, or 0 - * @id: Which LSM provided the context - * - * Fill in the lsmcontext from the provided information. - * This is a scaffolding function that will be removed when - * lsm_context integration is complete. - */ -static inline void lsmcontext_init(struct lsm_context *cp, char *context, - u32 size, int id) -{ - cp->id = id; - cp->context = context; - cp->len = size; -} - /* * Values used in the task_security_ops calls */ @@ -409,8 +390,8 @@ int security_sb_clone_mnt_opts(const struct super_block *oldsb, int security_move_mount(const struct path *from_path, const struct path *to_path); int security_dentry_init_security(struct dentry *dentry, int mode, const struct qstr *name, - const char **xattr_name, void **ctx, - u32 *ctxlen); + const char **xattr_name, + struct lsm_context *lsmcxt); int security_dentry_create_files_as(struct dentry *dentry, int mode, struct qstr *name, const struct cred *old, @@ -883,8 +864,7 @@ static inline int security_dentry_init_security(struct dentry *dentry, int mode, const struct qstr *name, const char **xattr_name, - void **ctx, - u32 *ctxlen) + struct lsm_context *lsmcxt) { return -EOPNOTSUPP; } diff --git a/security/security.c b/security/security.c index 1aecf1696c50..7523d14f31fb 100644 --- a/security/security.c +++ b/security/security.c @@ -1735,8 +1735,7 @@ void security_inode_free(struct inode *inode) * @mode: mode used to determine resource type * @name: name of the last path component * @xattr_name: name of the security/LSM xattr - * @ctx: pointer to the resulting LSM context - * @ctxlen: length of @ctx + * @lsmctx: pointer to the resulting LSM context * * Compute a context for a dentry as the inode is not yet available since NFSv4 * has no label backed by an EA anyway. It is important to note that @@ -1746,11 +1745,11 @@ void security_inode_free(struct inode *inode) */ int security_dentry_init_security(struct dentry *dentry, int mode, const struct qstr *name, - const char **xattr_name, void **ctx, - u32 *ctxlen) + const char **xattr_name, + struct lsm_context *lsmctx) { return call_int_hook(dentry_init_security, dentry, mode, name, - xattr_name, ctx, ctxlen); + xattr_name, lsmctx); } EXPORT_SYMBOL(security_dentry_init_security); diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 9254570de103..4f8d37ae769a 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -2869,8 +2869,8 @@ static void selinux_inode_free_security(struct inode *inode) static int selinux_dentry_init_security(struct dentry *dentry, int mode, const struct qstr *name, - const char **xattr_name, void **ctx, - u32 *ctxlen) + const char **xattr_name, + struct lsm_context *cp) { u32 newsid; int rc; @@ -2885,8 +2885,8 @@ static int selinux_dentry_init_security(struct dentry *dentry, int mode, if (xattr_name) *xattr_name = XATTR_NAME_SELINUX; - return security_sid_to_context(newsid, (char **)ctx, - ctxlen); + cp->id = LSM_ID_SELINUX; + return security_sid_to_context(newsid, &cp->context, &cp->len); } static int selinux_dentry_create_files_as(struct dentry *dentry, int mode, -- cgit v1.2.3 From a5874fde3c0884a33ed4145101052318c5e17c74 Mon Sep 17 00:00:00 2001 From: Mickaël Salaün Date: Thu, 12 Dec 2024 18:42:16 +0100 Subject: exec: Add a new AT_EXECVE_CHECK flag to execveat(2) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add a new AT_EXECVE_CHECK flag to execveat(2) to check if a file would be allowed for execution. The main use case is for script interpreters and dynamic linkers to check execution permission according to the kernel's security policy. Another use case is to add context to access logs e.g., which script (instead of interpreter) accessed a file. As any executable code, scripts could also use this check [1]. This is different from faccessat(2) + X_OK which only checks a subset of access rights (i.e. inode permission and mount options for regular files), but not the full context (e.g. all LSM access checks). The main use case for access(2) is for SUID processes to (partially) check access on behalf of their caller. The main use case for execveat(2) + AT_EXECVE_CHECK is to check if a script execution would be allowed, according to all the different restrictions in place. Because the use of AT_EXECVE_CHECK follows the exact kernel semantic as for a real execution, user space gets the same error codes. An interesting point of using execveat(2) instead of openat2(2) is that it decouples the check from the enforcement. Indeed, the security check can be logged (e.g. with audit) without blocking an execution environment not yet ready to enforce a strict security policy. LSMs can control or log execution requests with security_bprm_creds_for_exec(). However, to enforce a consistent and complete access control (e.g. on binary's dependencies) LSMs should restrict file executability, or measure executed files, with security_file_open() by checking file->f_flags & __FMODE_EXEC. Because AT_EXECVE_CHECK is dedicated to user space interpreters, it doesn't make sense for the kernel to parse the checked files, look for interpreters known to the kernel (e.g. ELF, shebang), and return ENOEXEC if the format is unknown. Because of that, security_bprm_check() is never called when AT_EXECVE_CHECK is used. It should be noted that script interpreters cannot directly use execveat(2) (without this new AT_EXECVE_CHECK flag) because this could lead to unexpected behaviors e.g., `python script.sh` could lead to Bash being executed to interpret the script. Unlike the kernel, script interpreters may just interpret the shebang as a simple comment, which should not change for backward compatibility reasons. Because scripts or libraries files might not currently have the executable permission set, or because we might want specific users to be allowed to run arbitrary scripts, the following patch provides a dynamic configuration mechanism with the SECBIT_EXEC_RESTRICT_FILE and SECBIT_EXEC_DENY_INTERACTIVE securebits. This is a redesign of the CLIP OS 4's O_MAYEXEC: https://github.com/clipos-archive/src_platform_clip-patches/blob/f5cb330d6b684752e403b4e41b39f7004d88e561/1901_open_mayexec.patch This patch has been used for more than a decade with customized script interpreters. Some examples can be found here: https://github.com/clipos-archive/clipos4_portage-overlay/search?q=O_MAYEXEC Cc: Al Viro Cc: Christian Brauner Cc: Kees Cook Acked-by: Paul Moore Reviewed-by: Serge Hallyn Reviewed-by: Jeff Xu Tested-by: Jeff Xu Link: https://docs.python.org/3/library/io.html#io.open_code [1] Signed-off-by: Mickaël Salaün Link: https://lore.kernel.org/r/20241212174223.389435-2-mic@digikod.net Signed-off-by: Kees Cook --- Documentation/userspace-api/check_exec.rst | 37 ++++++++++++++++++++++++++++++ Documentation/userspace-api/index.rst | 1 + fs/exec.c | 20 ++++++++++++++-- include/linux/binfmts.h | 7 +++++- include/uapi/linux/fcntl.h | 4 ++++ security/security.c | 10 ++++++++ 6 files changed, 76 insertions(+), 3 deletions(-) create mode 100644 Documentation/userspace-api/check_exec.rst (limited to 'security/security.c') diff --git a/Documentation/userspace-api/check_exec.rst b/Documentation/userspace-api/check_exec.rst new file mode 100644 index 000000000000..393dd7ca19c4 --- /dev/null +++ b/Documentation/userspace-api/check_exec.rst @@ -0,0 +1,37 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. Copyright © 2024 Microsoft Corporation + +=================== +Executability check +=================== + +AT_EXECVE_CHECK +=============== + +Passing the ``AT_EXECVE_CHECK`` flag to :manpage:`execveat(2)` only performs a +check on a regular file and returns 0 if execution of this file would be +allowed, ignoring the file format and then the related interpreter dependencies +(e.g. ELF libraries, script's shebang). + +Programs should always perform this check to apply kernel-level checks against +files that are not directly executed by the kernel but passed to a user space +interpreter instead. All files that contain executable code, from the point of +view of the interpreter, should be checked. However the result of this check +should only be enforced according to ``SECBIT_EXEC_RESTRICT_FILE`` or +``SECBIT_EXEC_DENY_INTERACTIVE.``. + +The main purpose of this flag is to improve the security and consistency of an +execution environment to ensure that direct file execution (e.g. +``./script.sh``) and indirect file execution (e.g. ``sh script.sh``) lead to +the same result. For instance, this can be used to check if a file is +trustworthy according to the caller's environment. + +In a secure environment, libraries and any executable dependencies should also +be checked. For instance, dynamic linking should make sure that all libraries +are allowed for execution to avoid trivial bypass (e.g. using ``LD_PRELOAD``). +For such secure execution environment to make sense, only trusted code should +be executable, which also requires integrity guarantees. + +To avoid race conditions leading to time-of-check to time-of-use issues, +``AT_EXECVE_CHECK`` should be used with ``AT_EMPTY_PATH`` to check against a +file descriptor instead of a path. diff --git a/Documentation/userspace-api/index.rst b/Documentation/userspace-api/index.rst index 274cc7546efc..6272bcf11296 100644 --- a/Documentation/userspace-api/index.rst +++ b/Documentation/userspace-api/index.rst @@ -35,6 +35,7 @@ Security-related interfaces mfd_noexec spec_ctrl tee + check_exec Devices and I/O =============== diff --git a/fs/exec.c b/fs/exec.c index 98cb7ba9983c..e3f461096e84 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -892,7 +892,8 @@ static struct file *do_open_execat(int fd, struct filename *name, int flags) .lookup_flags = LOOKUP_FOLLOW, }; - if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0) + if ((flags & + ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH | AT_EXECVE_CHECK)) != 0) return ERR_PTR(-EINVAL); if (flags & AT_SYMLINK_NOFOLLOW) open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW; @@ -1541,6 +1542,21 @@ static struct linux_binprm *alloc_bprm(int fd, struct filename *filename, int fl } bprm->interp = bprm->filename; + /* + * At this point, security_file_open() has already been called (with + * __FMODE_EXEC) and access control checks for AT_EXECVE_CHECK will + * stop just after the security_bprm_creds_for_exec() call in + * bprm_execve(). Indeed, the kernel should not try to parse the + * content of the file with exec_binprm() nor change the calling + * thread, which means that the following security functions will not + * be called: + * - security_bprm_check() + * - security_bprm_creds_from_file() + * - security_bprm_committing_creds() + * - security_bprm_committed_creds() + */ + bprm->is_check = !!(flags & AT_EXECVE_CHECK); + retval = bprm_mm_init(bprm); if (!retval) return bprm; @@ -1836,7 +1852,7 @@ static int bprm_execve(struct linux_binprm *bprm) /* Set the unchanging part of bprm->cred */ retval = security_bprm_creds_for_exec(bprm); - if (retval) + if (retval || bprm->is_check) goto out; retval = exec_binprm(bprm); diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index e6c00e860951..8ff0eb3644a1 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -42,7 +42,12 @@ struct linux_binprm { * Set when errors can no longer be returned to the * original userspace. */ - point_of_no_return:1; + point_of_no_return:1, + /* + * Set by user space to check executability according to the + * caller's environment. + */ + is_check:1; struct file *executable; /* Executable to pass to the interpreter */ struct file *interpreter; struct file *file; diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h index 6e6907e63bfc..a15ac2fa4b20 100644 --- a/include/uapi/linux/fcntl.h +++ b/include/uapi/linux/fcntl.h @@ -155,4 +155,8 @@ #define AT_HANDLE_MNT_ID_UNIQUE 0x001 /* Return the u64 unique mount ID. */ #define AT_HANDLE_CONNECTABLE 0x002 /* Request a connectable file handle */ +/* Flags for execveat2(2). */ +#define AT_EXECVE_CHECK 0x10000 /* Only perform a check if execution + would be allowed. */ + #endif /* _UAPI_LINUX_FCNTL_H */ diff --git a/security/security.c b/security/security.c index 09664e09fec9..dae7e903947f 100644 --- a/security/security.c +++ b/security/security.c @@ -1248,6 +1248,12 @@ int security_vm_enough_memory_mm(struct mm_struct *mm, long pages) * to 1 if AT_SECURE should be set to request libc enable secure mode. @bprm * contains the linux_binprm structure. * + * If execveat(2) is called with the AT_EXECVE_CHECK flag, bprm->is_check is + * set. The result must be the same as without this flag even if the execution + * will never really happen and @bprm will always be dropped. + * + * This hook must not change current->cred, only @bprm->cred. + * * Return: Returns 0 if the hook is successful and permission is granted. */ int security_bprm_creds_for_exec(struct linux_binprm *bprm) @@ -3098,6 +3104,10 @@ int security_file_receive(struct file *file) * Save open-time permission checking state for later use upon file_permission, * and recheck access if anything has changed since inode_permission. * + * We can check if a file is opened for execution (e.g. execve(2) call), either + * directly or indirectly (e.g. ELF's ld.so) by checking file->f_flags & + * __FMODE_EXEC . + * * Return: Returns 0 if permission is granted. */ int security_file_open(struct file *file) -- cgit v1.2.3 From 241d6a66404c975415fd0facaf70d61b37248f50 Mon Sep 17 00:00:00 2001 From: Colin Ian King Date: Tue, 12 Nov 2024 12:45:32 +0000 Subject: security: remove redundant assignment to return variable In the case where rc is equal to EOPNOTSUPP it is being reassigned a new value of zero that is never read. The following continue statement loops back to the next iteration of the lsm_for_each_hook loop and rc is being re-assigned a new value from the call to getselfattr. The assignment is redundant and can be removed. Signed-off-by: Colin Ian King Reviewed-by: Serge Hallyn [PM: subj tweak] Signed-off-by: Paul Moore --- security/security.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) (limited to 'security/security.c') diff --git a/security/security.c b/security/security.c index 7523d14f31fb..39df4451455b 100644 --- a/security/security.c +++ b/security/security.c @@ -4138,10 +4138,8 @@ int security_getselfattr(unsigned int attr, struct lsm_ctx __user *uctx, if (base) uctx = (struct lsm_ctx __user *)(base + total); rc = scall->hl->hook.getselfattr(attr, uctx, &entrysize, flags); - if (rc == -EOPNOTSUPP) { - rc = 0; + if (rc == -EOPNOTSUPP) continue; - } if (rc == -E2BIG) { rc = 0; left = 0; -- cgit v1.2.3