From b493af3a66e067f93e5e03465507866ddeabff9e Mon Sep 17 00:00:00 2001 From: Alexey Gladkov Date: Mon, 23 Aug 2021 18:16:33 +0200 Subject: ucounts: Increase ucounts reference counter before the security hook [ Upstream commit bbb6d0f3e1feb43d663af089c7dedb23be6a04fb ] We need to increment the ucounts reference counter befor security_prepare_creds() because this function may fail and abort_creds() will try to decrement this reference. [ 96.465056][ T8641] FAULT_INJECTION: forcing a failure. [ 96.465056][ T8641] name fail_page_alloc, interval 1, probability 0, space 0, times 0 [ 96.478453][ T8641] CPU: 1 PID: 8641 Comm: syz-executor668 Not tainted 5.14.0-rc6-syzkaller #0 [ 96.487215][ T8641] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 96.497254][ T8641] Call Trace: [ 96.500517][ T8641] dump_stack_lvl+0x1d3/0x29f [ 96.505758][ T8641] ? show_regs_print_info+0x12/0x12 [ 96.510944][ T8641] ? log_buf_vmcoreinfo_setup+0x498/0x498 [ 96.516652][ T8641] should_fail+0x384/0x4b0 [ 96.521141][ T8641] prepare_alloc_pages+0x1d1/0x5a0 [ 96.526236][ T8641] __alloc_pages+0x14d/0x5f0 [ 96.530808][ T8641] ? __rmqueue_pcplist+0x2030/0x2030 [ 96.536073][ T8641] ? lockdep_hardirqs_on_prepare+0x3e2/0x750 [ 96.542056][ T8641] ? alloc_pages+0x3f3/0x500 [ 96.546635][ T8641] allocate_slab+0xf1/0x540 [ 96.551120][ T8641] ___slab_alloc+0x1cf/0x350 [ 96.555689][ T8641] ? kzalloc+0x1d/0x30 [ 96.559740][ T8641] __kmalloc+0x2e7/0x390 [ 96.563980][ T8641] ? kzalloc+0x1d/0x30 [ 96.568029][ T8641] kzalloc+0x1d/0x30 [ 96.571903][ T8641] security_prepare_creds+0x46/0x220 [ 96.577174][ T8641] prepare_creds+0x411/0x640 [ 96.581747][ T8641] __sys_setfsuid+0xe2/0x3a0 [ 96.586333][ T8641] do_syscall_64+0x3d/0xb0 [ 96.590739][ T8641] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 96.596611][ T8641] RIP: 0033:0x445a69 [ 96.600483][ T8641] Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 [ 96.620152][ T8641] RSP: 002b:00007f1054173318 EFLAGS: 00000246 ORIG_RAX: 000000000000007a [ 96.628543][ T8641] RAX: ffffffffffffffda RBX: 00000000004ca4c8 RCX: 0000000000445a69 [ 96.636600][ T8641] RDX: 0000000000000010 RSI: 00007f10541732f0 RDI: 0000000000000000 [ 96.644550][ T8641] RBP: 00000000004ca4c0 R08: 0000000000000001 R09: 0000000000000000 [ 96.652500][ T8641] R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004ca4cc [ 96.660631][ T8641] R13: 00007fffffe0b62f R14: 00007f1054173400 R15: 0000000000022000 Fixes: 905ae01c4ae2 ("Add a reference to ucounts for each cred") Reported-by: syzbot+01985d7909f9468f013c@syzkaller.appspotmail.com Signed-off-by: Alexey Gladkov Link: https://lkml.kernel.org/r/97433b1742c3331f02ad92de5a4f07d673c90613.1629735352.git.legion@kernel.org Signed-off-by: Eric W. Biederman Signed-off-by: Sasha Levin --- kernel/cred.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) (limited to 'kernel/cred.c') diff --git a/kernel/cred.c b/kernel/cred.c index 098213d4a39c..8c0983fa794a 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -286,13 +286,13 @@ struct cred *prepare_creds(void) new->security = NULL; #endif - if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) - goto error; - new->ucounts = get_ucounts(new->ucounts); if (!new->ucounts) goto error; + if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) + goto error; + validate_creds(new); return new; @@ -753,13 +753,13 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon) #ifdef CONFIG_SECURITY new->security = NULL; #endif - if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) - goto error; - new->ucounts = get_ucounts(new->ucounts); if (!new->ucounts) goto error; + if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) + goto error; + put_cred(old); validate_creds(new); return new; -- cgit v1.2.3 From 0c1443874e1cb359b377a0e383c0dcce81aefa12 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Fri, 3 Sep 2021 16:06:21 +0200 Subject: Revert "ucounts: Increase ucounts reference counter before the security hook" This reverts commit b493af3a66e067f93e5e03465507866ddeabff9e which is commit bbb6d0f3e1feb43d663af089c7dedb23be6a04fb upstream. The "original" commit 905ae01c4ae2 ("Add a reference to ucounts for each cred"), should not have been applied to the 5.10.y tree, so revert it, and the follow-on fixup patches as well. Reported-by: "Eric W. Biederman" Link: https://lore.kernel.org/r/87v93k4bl6.fsf@disp2133 Cc: Alexey Gladkov Cc: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- kernel/cred.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) (limited to 'kernel/cred.c') diff --git a/kernel/cred.c b/kernel/cred.c index 8c0983fa794a..098213d4a39c 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -286,11 +286,11 @@ struct cred *prepare_creds(void) new->security = NULL; #endif - new->ucounts = get_ucounts(new->ucounts); - if (!new->ucounts) + if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) goto error; - if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) + new->ucounts = get_ucounts(new->ucounts); + if (!new->ucounts) goto error; validate_creds(new); @@ -753,11 +753,11 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon) #ifdef CONFIG_SECURITY new->security = NULL; #endif - new->ucounts = get_ucounts(new->ucounts); - if (!new->ucounts) + if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) goto error; - if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) + new->ucounts = get_ucounts(new->ucounts); + if (!new->ucounts) goto error; put_cred(old); -- cgit v1.2.3 From 1aa3f27e592dea3b6cbc5ef5ec979ba5f511d410 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Fri, 3 Sep 2021 16:06:40 +0200 Subject: Revert "cred: add missing return error code when set_cred_ucounts() failed" This reverts commit 0855952ed4f1a6861fbb0e5d684efd447d7347c9 which is commit 5e6b8a50a7cec5686ee2c4bda1d49899c79a7eae upstream. The "original" commit 905ae01c4ae2 ("Add a reference to ucounts for each cred"), should not have been applied to the 5.10.y tree, so revert it, and the follow-on fixup patches as well. Reported-by: "Eric W. Biederman" Link: https://lore.kernel.org/r/87v93k4bl6.fsf@disp2133 Cc: Yang Yingliang Cc: Alexey Gladkov Cc: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- kernel/cred.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'kernel/cred.c') diff --git a/kernel/cred.c b/kernel/cred.c index 098213d4a39c..58a8a9e24347 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -372,8 +372,7 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags) ret = create_user_ns(new); if (ret < 0) goto error_put; - ret = set_cred_ucounts(new); - if (ret < 0) + if (set_cred_ucounts(new) < 0) goto error_put; } -- cgit v1.2.3 From ae16b7c668378ea00eb60ab9d29e0d46b0e7aa15 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Fri, 3 Sep 2021 16:06:50 +0200 Subject: Revert "Add a reference to ucounts for each cred" This reverts commit b2c4d9a33cc2dec7466f97eba2c4dd571ad798a5 which is commit 905ae01c4ae2ae3df05bb141801b1db4b7d83c61 upstream. This commit should not have been applied to the 5.10.y stable tree, so revert it. Reported-by: "Eric W. Biederman" Link: https://lore.kernel.org/r/87v93k4bl6.fsf@disp2133 Cc: Alexey Gladkov Cc: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/exec.c | 4 ---- include/linux/cred.h | 2 -- include/linux/user_namespace.h | 4 ---- kernel/cred.c | 40 ---------------------------------------- kernel/fork.c | 6 ------ kernel/sys.c | 12 ------------ kernel/ucount.c | 40 +++------------------------------------- kernel/user_namespace.c | 3 --- 8 files changed, 3 insertions(+), 108 deletions(-) (limited to 'kernel/cred.c') diff --git a/fs/exec.c b/fs/exec.c index c7a4ef8df305..ca89e0e3ef10 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1347,10 +1347,6 @@ int begin_new_exec(struct linux_binprm * bprm) WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1); flush_signal_handlers(me, 0); - retval = set_cred_ucounts(bprm->cred); - if (retval < 0) - goto out_unlock; - /* * install the new credentials for this executable */ diff --git a/include/linux/cred.h b/include/linux/cred.h index ad160e5fe5c6..18639c069263 100644 --- a/include/linux/cred.h +++ b/include/linux/cred.h @@ -144,7 +144,6 @@ struct cred { #endif struct user_struct *user; /* real user ID subscription */ struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */ - struct ucounts *ucounts; struct group_info *group_info; /* supplementary groups for euid/fsgid */ /* RCU deletion */ union { @@ -171,7 +170,6 @@ extern int set_security_override_from_ctx(struct cred *, const char *); extern int set_create_files_as(struct cred *, struct inode *); extern int cred_fscmp(const struct cred *, const struct cred *); extern void __init cred_init(void); -extern int set_cred_ucounts(struct cred *); /* * check for validity of credentials diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h index e1bd560da1cd..7616c7bf4b24 100644 --- a/include/linux/user_namespace.h +++ b/include/linux/user_namespace.h @@ -101,15 +101,11 @@ struct ucounts { }; extern struct user_namespace init_user_ns; -extern struct ucounts init_ucounts; bool setup_userns_sysctls(struct user_namespace *ns); void retire_userns_sysctls(struct user_namespace *ns); struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, enum ucount_type type); void dec_ucount(struct ucounts *ucounts, enum ucount_type type); -struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid); -struct ucounts *get_ucounts(struct ucounts *ucounts); -void put_ucounts(struct ucounts *ucounts); #ifdef CONFIG_USER_NS diff --git a/kernel/cred.c b/kernel/cred.c index 58a8a9e24347..421b1149c651 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -60,7 +60,6 @@ struct cred init_cred = { .user = INIT_USER, .user_ns = &init_user_ns, .group_info = &init_groups, - .ucounts = &init_ucounts, }; static inline void set_cred_subscribers(struct cred *cred, int n) @@ -120,8 +119,6 @@ static void put_cred_rcu(struct rcu_head *rcu) if (cred->group_info) put_group_info(cred->group_info); free_uid(cred->user); - if (cred->ucounts) - put_ucounts(cred->ucounts); put_user_ns(cred->user_ns); kmem_cache_free(cred_jar, cred); } @@ -225,7 +222,6 @@ struct cred *cred_alloc_blank(void) #ifdef CONFIG_DEBUG_CREDENTIALS new->magic = CRED_MAGIC; #endif - new->ucounts = get_ucounts(&init_ucounts); if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0) goto error; @@ -288,11 +284,6 @@ struct cred *prepare_creds(void) if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) goto error; - - new->ucounts = get_ucounts(new->ucounts); - if (!new->ucounts) - goto error; - validate_creds(new); return new; @@ -372,8 +363,6 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags) ret = create_user_ns(new); if (ret < 0) goto error_put; - if (set_cred_ucounts(new) < 0) - goto error_put; } #ifdef CONFIG_KEYS @@ -664,31 +653,6 @@ int cred_fscmp(const struct cred *a, const struct cred *b) } EXPORT_SYMBOL(cred_fscmp); -int set_cred_ucounts(struct cred *new) -{ - struct task_struct *task = current; - const struct cred *old = task->real_cred; - struct ucounts *old_ucounts = new->ucounts; - - if (new->user == old->user && new->user_ns == old->user_ns) - return 0; - - /* - * This optimization is needed because alloc_ucounts() uses locks - * for table lookups. - */ - if (old_ucounts && old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->euid)) - return 0; - - if (!(new->ucounts = alloc_ucounts(new->user_ns, new->euid))) - return -EAGAIN; - - if (old_ucounts) - put_ucounts(old_ucounts); - - return 0; -} - /* * initialise the credentials stuff */ @@ -755,10 +719,6 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon) if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) goto error; - new->ucounts = get_ucounts(new->ucounts); - if (!new->ucounts) - goto error; - put_cred(old); validate_creds(new); return new; diff --git a/kernel/fork.c b/kernel/fork.c index 096945ef49ad..9705439439fe 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2960,12 +2960,6 @@ int ksys_unshare(unsigned long unshare_flags) if (err) goto bad_unshare_cleanup_cred; - if (new_cred) { - err = set_cred_ucounts(new_cred); - if (err) - goto bad_unshare_cleanup_cred; - } - if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) { if (do_sysvsem) { /* diff --git a/kernel/sys.c b/kernel/sys.c index 0670e824e019..a730c03ee607 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -552,10 +552,6 @@ long __sys_setreuid(uid_t ruid, uid_t euid) if (retval < 0) goto error; - retval = set_cred_ucounts(new); - if (retval < 0) - goto error; - return commit_creds(new); error: @@ -614,10 +610,6 @@ long __sys_setuid(uid_t uid) if (retval < 0) goto error; - retval = set_cred_ucounts(new); - if (retval < 0) - goto error; - return commit_creds(new); error: @@ -693,10 +685,6 @@ long __sys_setresuid(uid_t ruid, uid_t euid, uid_t suid) if (retval < 0) goto error; - retval = set_cred_ucounts(new); - if (retval < 0) - goto error; - return commit_creds(new); error: diff --git a/kernel/ucount.c b/kernel/ucount.c index 9894795043c4..11b1596e2542 100644 --- a/kernel/ucount.c +++ b/kernel/ucount.c @@ -8,12 +8,6 @@ #include #include -struct ucounts init_ucounts = { - .ns = &init_user_ns, - .uid = GLOBAL_ROOT_UID, - .count = 1, -}; - #define UCOUNTS_HASHTABLE_BITS 10 static struct hlist_head ucounts_hashtable[(1 << UCOUNTS_HASHTABLE_BITS)]; static DEFINE_SPINLOCK(ucounts_lock); @@ -131,15 +125,7 @@ static struct ucounts *find_ucounts(struct user_namespace *ns, kuid_t uid, struc return NULL; } -static void hlist_add_ucounts(struct ucounts *ucounts) -{ - struct hlist_head *hashent = ucounts_hashentry(ucounts->ns, ucounts->uid); - spin_lock_irq(&ucounts_lock); - hlist_add_head(&ucounts->node, hashent); - spin_unlock_irq(&ucounts_lock); -} - -struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid) +static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) { struct hlist_head *hashent = ucounts_hashentry(ns, uid); struct ucounts *ucounts, *new; @@ -174,26 +160,7 @@ struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid) return ucounts; } -struct ucounts *get_ucounts(struct ucounts *ucounts) -{ - unsigned long flags; - - if (!ucounts) - return NULL; - - spin_lock_irqsave(&ucounts_lock, flags); - if (ucounts->count == INT_MAX) { - WARN_ONCE(1, "ucounts: counter has reached its maximum value"); - ucounts = NULL; - } else { - ucounts->count += 1; - } - spin_unlock_irqrestore(&ucounts_lock, flags); - - return ucounts; -} - -void put_ucounts(struct ucounts *ucounts) +static void put_ucounts(struct ucounts *ucounts) { unsigned long flags; @@ -227,7 +194,7 @@ struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid, { struct ucounts *ucounts, *iter, *bad; struct user_namespace *tns; - ucounts = alloc_ucounts(ns, uid); + ucounts = get_ucounts(ns, uid); for (iter = ucounts; iter; iter = tns->ucounts) { int max; tns = iter->ns; @@ -270,7 +237,6 @@ static __init int user_namespace_sysctl_init(void) BUG_ON(!user_header); BUG_ON(!setup_userns_sysctls(&init_user_ns)); #endif - hlist_add_ucounts(&init_ucounts); return 0; } subsys_initcall(user_namespace_sysctl_init); diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 8206a13c81eb..ce396ea4de60 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -1340,9 +1340,6 @@ static int userns_install(struct nsset *nsset, struct ns_common *ns) put_user_ns(cred->user_ns); set_cred_user_ns(cred, get_user_ns(user_ns)); - if (set_cred_ucounts(cred) < 0) - return -EINVAL; - return 0; } -- cgit v1.2.3