diff options
Diffstat (limited to 'security/landlock')
| -rw-r--r-- | security/landlock/errata.h | 99 | ||||
| -rw-r--r-- | security/landlock/errata/abi-4.h | 15 | ||||
| -rw-r--r-- | security/landlock/errata/abi-6.h | 19 | ||||
| -rw-r--r-- | security/landlock/fs.c | 50 | ||||
| -rw-r--r-- | security/landlock/net.c | 3 | ||||
| -rw-r--r-- | security/landlock/setup.c | 38 | ||||
| -rw-r--r-- | security/landlock/setup.h | 3 | ||||
| -rw-r--r-- | security/landlock/syscalls.c | 22 | ||||
| -rw-r--r-- | security/landlock/task.c | 12 |
9 files changed, 239 insertions, 22 deletions
diff --git a/security/landlock/errata.h b/security/landlock/errata.h new file mode 100644 index 000000000000..8e626accac10 --- /dev/null +++ b/security/landlock/errata.h @@ -0,0 +1,99 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Landlock - Errata information + * + * Copyright © 2025 Microsoft Corporation + */ + +#ifndef _SECURITY_LANDLOCK_ERRATA_H +#define _SECURITY_LANDLOCK_ERRATA_H + +#include <linux/init.h> + +struct landlock_erratum { + const int abi; + const u8 number; +}; + +/* clang-format off */ +#define LANDLOCK_ERRATUM(NUMBER) \ + { \ + .abi = LANDLOCK_ERRATA_ABI, \ + .number = NUMBER, \ + }, +/* clang-format on */ + +/* + * Some fixes may require user space to check if they are applied on the running + * kernel before using a specific feature. For instance, this applies when a + * restriction was previously too restrictive and is now getting relaxed (for + * compatibility or semantic reasons). However, non-visible changes for + * legitimate use (e.g. security fixes) do not require an erratum. + */ +static const struct landlock_erratum landlock_errata_init[] __initconst = { + +/* + * Only Sparse may not implement __has_include. If a compiler does not + * implement __has_include, a warning will be printed at boot time (see + * setup.c). + */ +#ifdef __has_include + +#define LANDLOCK_ERRATA_ABI 1 +#if __has_include("errata/abi-1.h") +#include "errata/abi-1.h" +#endif +#undef LANDLOCK_ERRATA_ABI + +#define LANDLOCK_ERRATA_ABI 2 +#if __has_include("errata/abi-2.h") +#include "errata/abi-2.h" +#endif +#undef LANDLOCK_ERRATA_ABI + +#define LANDLOCK_ERRATA_ABI 3 +#if __has_include("errata/abi-3.h") +#include "errata/abi-3.h" +#endif +#undef LANDLOCK_ERRATA_ABI + +#define LANDLOCK_ERRATA_ABI 4 +#if __has_include("errata/abi-4.h") +#include "errata/abi-4.h" +#endif +#undef LANDLOCK_ERRATA_ABI + +#define LANDLOCK_ERRATA_ABI 5 +#if __has_include("errata/abi-5.h") +#include "errata/abi-5.h" +#endif +#undef LANDLOCK_ERRATA_ABI + +#define LANDLOCK_ERRATA_ABI 6 +#if __has_include("errata/abi-6.h") +#include "errata/abi-6.h" +#endif +#undef LANDLOCK_ERRATA_ABI + +/* + * For each new erratum, we need to include all the ABI files up to the impacted + * ABI to make all potential future intermediate errata easy to backport. + * + * If such change involves more than one ABI addition, then it must be in a + * dedicated commit with the same Fixes tag as used for the actual fix. + * + * Each commit creating a new security/landlock/errata/abi-*.h file must have a + * Depends-on tag to reference the commit that previously added the line to + * include this new file, except if the original Fixes tag is enough. + * + * Each erratum must be documented in its related ABI file, and a dedicated + * commit must update Documentation/userspace-api/landlock.rst to include this + * erratum. This commit will not be backported. + */ + +#endif + + {} +}; + +#endif /* _SECURITY_LANDLOCK_ERRATA_H */ diff --git a/security/landlock/errata/abi-4.h b/security/landlock/errata/abi-4.h new file mode 100644 index 000000000000..c052ee54f89f --- /dev/null +++ b/security/landlock/errata/abi-4.h @@ -0,0 +1,15 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ + +/** + * DOC: erratum_1 + * + * Erratum 1: TCP socket identification + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + * + * This fix addresses an issue where IPv4 and IPv6 stream sockets (e.g., SMC, + * MPTCP, or SCTP) were incorrectly restricted by TCP access rights during + * :manpage:`bind(2)` and :manpage:`connect(2)` operations. This change ensures + * that only TCP sockets are subject to TCP access rights, allowing other + * protocols to operate without unnecessary restrictions. + */ +LANDLOCK_ERRATUM(1) diff --git a/security/landlock/errata/abi-6.h b/security/landlock/errata/abi-6.h new file mode 100644 index 000000000000..df7bc0e1fdf4 --- /dev/null +++ b/security/landlock/errata/abi-6.h @@ -0,0 +1,19 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ + +/** + * DOC: erratum_2 + * + * Erratum 2: Scoped signal handling + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + * + * This fix addresses an issue where signal scoping was overly restrictive, + * preventing sandboxed threads from signaling other threads within the same + * process if they belonged to different domains. Because threads are not + * security boundaries, user space might assume that any thread within the same + * process can send signals between themselves (see :manpage:`nptl(7)` and + * :manpage:`libpsx(3)`). Consistent with :manpage:`ptrace(2)` behavior, direct + * interaction between threads of the same process should always be allowed. + * This change ensures that any thread is allowed to send signals to any other + * thread within the same process, regardless of their domain. + */ +LANDLOCK_ERRATUM(2) diff --git a/security/landlock/fs.c b/security/landlock/fs.c index e31b97a9f175..511e6ae8b79c 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -27,7 +27,9 @@ #include <linux/mount.h> #include <linux/namei.h> #include <linux/path.h> +#include <linux/pid.h> #include <linux/rcupdate.h> +#include <linux/sched/signal.h> #include <linux/spinlock.h> #include <linux/stat.h> #include <linux/types.h> @@ -937,10 +939,6 @@ static access_mask_t get_mode_access(const umode_t mode) switch (mode & S_IFMT) { case S_IFLNK: return LANDLOCK_ACCESS_FS_MAKE_SYM; - case 0: - /* A zero mode translates to S_IFREG. */ - case S_IFREG: - return LANDLOCK_ACCESS_FS_MAKE_REG; case S_IFDIR: return LANDLOCK_ACCESS_FS_MAKE_DIR; case S_IFCHR: @@ -951,9 +949,12 @@ static access_mask_t get_mode_access(const umode_t mode) return LANDLOCK_ACCESS_FS_MAKE_FIFO; case S_IFSOCK: return LANDLOCK_ACCESS_FS_MAKE_SOCK; + case S_IFREG: + case 0: + /* A zero mode translates to S_IFREG. */ default: - WARN_ON_ONCE(1); - return 0; + /* Treats weird files as regular files. */ + return LANDLOCK_ACCESS_FS_MAKE_REG; } } @@ -1624,21 +1625,46 @@ static int hook_file_ioctl_compat(struct file *file, unsigned int cmd, return -EACCES; } -static void hook_file_set_fowner(struct file *file) +/* + * Always allow sending signals between threads of the same process. This + * ensures consistency with hook_task_kill(). + */ +static bool control_current_fowner(struct fown_struct *const fown) { - struct landlock_ruleset *new_dom, *prev_dom; + struct task_struct *p; /* * Lock already held by __f_setown(), see commit 26f204380a3c ("fs: Fix * file_set_fowner LSM hook inconsistencies"). */ - lockdep_assert_held(&file_f_owner(file)->lock); - new_dom = landlock_get_current_domain(); - landlock_get_ruleset(new_dom); + lockdep_assert_held(&fown->lock); + + /* + * Some callers (e.g. fcntl_dirnotify) may not be in an RCU read-side + * critical section. + */ + guard(rcu)(); + p = pid_task(fown->pid, fown->pid_type); + if (!p) + return true; + + return !same_thread_group(p, current); +} + +static void hook_file_set_fowner(struct file *file) +{ + struct landlock_ruleset *prev_dom; + struct landlock_ruleset *new_dom = NULL; + + if (control_current_fowner(file_f_owner(file))) { + new_dom = landlock_get_current_domain(); + landlock_get_ruleset(new_dom); + } + prev_dom = landlock_file(file)->fown_domain; landlock_file(file)->fown_domain = new_dom; - /* Called in an RCU read-side critical section. */ + /* May be called in an RCU read-side critical section. */ landlock_put_ruleset_deferred(prev_dom); } diff --git a/security/landlock/net.c b/security/landlock/net.c index d5dcc4407a19..104b6c01fe50 100644 --- a/security/landlock/net.c +++ b/security/landlock/net.c @@ -63,8 +63,7 @@ static int current_check_access_socket(struct socket *const sock, if (WARN_ON_ONCE(dom->num_layers < 1)) return -EACCES; - /* Checks if it's a (potential) TCP socket. */ - if (sock->type != SOCK_STREAM) + if (!sk_is_tcp(sock->sk)) return 0; /* Checks for minimal header length to safely read sa_family. */ diff --git a/security/landlock/setup.c b/security/landlock/setup.c index 28519a45b11f..0c85ea27e409 100644 --- a/security/landlock/setup.c +++ b/security/landlock/setup.c @@ -6,12 +6,14 @@ * Copyright © 2018-2020 ANSSI */ +#include <linux/bits.h> #include <linux/init.h> #include <linux/lsm_hooks.h> #include <uapi/linux/lsm.h> #include "common.h" #include "cred.h" +#include "errata.h" #include "fs.h" #include "net.h" #include "setup.h" @@ -19,6 +21,11 @@ bool landlock_initialized __ro_after_init = false; +const struct lsm_id landlock_lsmid = { + .name = LANDLOCK_NAME, + .id = LSM_ID_LANDLOCK, +}; + struct lsm_blob_sizes landlock_blob_sizes __ro_after_init = { .lbs_cred = sizeof(struct landlock_cred_security), .lbs_file = sizeof(struct landlock_file_security), @@ -26,13 +33,36 @@ struct lsm_blob_sizes landlock_blob_sizes __ro_after_init = { .lbs_superblock = sizeof(struct landlock_superblock_security), }; -const struct lsm_id landlock_lsmid = { - .name = LANDLOCK_NAME, - .id = LSM_ID_LANDLOCK, -}; +int landlock_errata __ro_after_init; + +static void __init compute_errata(void) +{ + size_t i; + +#ifndef __has_include + /* + * This is a safeguard to make sure the compiler implements + * __has_include (see errata.h). + */ + WARN_ON_ONCE(1); + return; +#endif + + for (i = 0; landlock_errata_init[i].number; i++) { + const int prev_errata = landlock_errata; + + if (WARN_ON_ONCE(landlock_errata_init[i].abi > + landlock_abi_version)) + continue; + + landlock_errata |= BIT(landlock_errata_init[i].number - 1); + WARN_ON_ONCE(prev_errata == landlock_errata); + } +} static int __init landlock_init(void) { + compute_errata(); landlock_add_cred_hooks(); landlock_add_task_hooks(); landlock_add_fs_hooks(); diff --git a/security/landlock/setup.h b/security/landlock/setup.h index c4252d46d49d..fca307c35fee 100644 --- a/security/landlock/setup.h +++ b/security/landlock/setup.h @@ -11,7 +11,10 @@ #include <linux/lsm_hooks.h> +extern const int landlock_abi_version; + extern bool landlock_initialized; +extern int landlock_errata; extern struct lsm_blob_sizes landlock_blob_sizes; extern const struct lsm_id landlock_lsmid; diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c index c097d356fa45..4fa2d09f657a 100644 --- a/security/landlock/syscalls.c +++ b/security/landlock/syscalls.c @@ -159,7 +159,9 @@ static const struct file_operations ruleset_fops = { * the new ruleset. * @size: Size of the pointed &struct landlock_ruleset_attr (needed for * backward and forward compatibility). - * @flags: Supported value: %LANDLOCK_CREATE_RULESET_VERSION. + * @flags: Supported value: + * - %LANDLOCK_CREATE_RULESET_VERSION + * - %LANDLOCK_CREATE_RULESET_ERRATA * * This system call enables to create a new Landlock ruleset, and returns the * related file descriptor on success. @@ -168,6 +170,10 @@ static const struct file_operations ruleset_fops = { * 0, then the returned value is the highest supported Landlock ABI version * (starting at 1). * + * If @flags is %LANDLOCK_CREATE_RULESET_ERRATA and @attr is NULL and @size is + * 0, then the returned value is a bitmask of fixed issues for the current + * Landlock ABI version. + * * Possible returned errors are: * * - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time; @@ -191,9 +197,15 @@ SYSCALL_DEFINE3(landlock_create_ruleset, return -EOPNOTSUPP; if (flags) { - if ((flags == LANDLOCK_CREATE_RULESET_VERSION) && !attr && - !size) - return LANDLOCK_ABI_VERSION; + if (attr || size) + return -EINVAL; + + if (flags == LANDLOCK_CREATE_RULESET_VERSION) + return landlock_abi_version; + + if (flags == LANDLOCK_CREATE_RULESET_ERRATA) + return landlock_errata; + return -EINVAL; } @@ -234,6 +246,8 @@ SYSCALL_DEFINE3(landlock_create_ruleset, return ruleset_fd; } +const int landlock_abi_version = LANDLOCK_ABI_VERSION; + /* * Returns an owned ruleset from a FD. It is thus needed to call * landlock_put_ruleset() on the return value. diff --git a/security/landlock/task.c b/security/landlock/task.c index dc7dab78392e..4578ce6e319d 100644 --- a/security/landlock/task.c +++ b/security/landlock/task.c @@ -13,6 +13,7 @@ #include <linux/lsm_hooks.h> #include <linux/rcupdate.h> #include <linux/sched.h> +#include <linux/sched/signal.h> #include <net/af_unix.h> #include <net/sock.h> @@ -264,6 +265,17 @@ static int hook_task_kill(struct task_struct *const p, /* Dealing with USB IO. */ dom = landlock_cred(cred)->domain; } else { + /* + * Always allow sending signals between threads of the same process. + * This is required for process credential changes by the Native POSIX + * Threads Library and implemented by the set*id(2) wrappers and + * libcap(3) with tgkill(2). See nptl(7) and libpsx(3). + * + * This exception is similar to the __ptrace_may_access() one. + */ + if (same_thread_group(p, current)) + return 0; + dom = landlock_get_current_domain(); } dom = landlock_get_applicable_domain(dom, signal_scope); |