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Date: Mon, 13 Jun 2022 13:28:07 -0700 From: Micah Morton <mortonm@...omium.org> To: linux-security-module@...r.kernel.org Cc: keescook@...omium.org, jmorris@...ei.org, serge@...lyn.com, linux-kernel@...r.kernel.org, Micah Morton <mortonm@...omium.org> Subject: [PATCH 1/2] security: Add LSM hook to setgroups() syscall Give the LSM framework the ability to filter setgroups() syscalls. There are already analagous hooks for the set*uid() and set*gid() syscalls. The SafeSetID LSM will use this new hook to ensure setgroups() calls are allowed by the installed security policy. Signed-off-by: Micah Morton <mortonm@...omium.org> --- Developed on 5.18 include/linux/lsm_hook_defs.h | 1 + include/linux/lsm_hooks.h | 7 +++++++ include/linux/security.h | 7 +++++++ kernel/groups.c | 12 ++++++++++++ security/security.c | 5 +++++ 5 files changed, 32 insertions(+) diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index db924fe379c9..c01063ec4be7 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -201,6 +201,7 @@ LSM_HOOK(int, 0, task_fix_setuid, struct cred *new, const struct cred *old, int flags) LSM_HOOK(int, 0, task_fix_setgid, struct cred *new, const struct cred * old, int flags) +LSM_HOOK(int, 0, task_fix_setgroups, struct cred *new, const struct cred * old) LSM_HOOK(int, 0, task_setpgid, struct task_struct *p, pid_t pgid) LSM_HOOK(int, 0, task_getpgid, struct task_struct *p) LSM_HOOK(int, 0, task_getsid, struct task_struct *p) diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 419b5febc3ca..b5143d9a1127 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -701,6 +701,13 @@ * @old is the set of credentials that are being replaced. * @flags contains one of the LSM_SETID_* values. * Return 0 on success. + * @task_fix_setgroups: + * Update the module's state after setting the supplementary group + * identity attributes of the current process. + * @new is the set of credentials that will be installed. Modifications + * should be made to this rather than to @current->cred. + * @old is the set of credentials that are being replaced. + * Return 0 on success. * @task_setpgid: * Check permission before setting the process group identifier of the * process @p to @pgid. diff --git a/include/linux/security.h b/include/linux/security.h index 25b3ef71f495..d111ff830742 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -413,6 +413,7 @@ int security_task_fix_setuid(struct cred *new, const struct cred *old, int flags); int security_task_fix_setgid(struct cred *new, const struct cred *old, int flags); +int security_task_fix_setgroups(struct cred *new, const struct cred *old); int security_task_setpgid(struct task_struct *p, pid_t pgid); int security_task_getpgid(struct task_struct *p); int security_task_getsid(struct task_struct *p); @@ -1096,6 +1097,12 @@ static inline int security_task_fix_setgid(struct cred *new, return 0; } +static inline int security_task_fix_setgroups(struct cred *new, + const struct cred *old) +{ + return 0; +} + static inline int security_task_setpgid(struct task_struct *p, pid_t pgid) { return 0; diff --git a/kernel/groups.c b/kernel/groups.c index 787b381c7c00..c085f54d8dbb 100644 --- a/kernel/groups.c +++ b/kernel/groups.c @@ -134,13 +134,25 @@ EXPORT_SYMBOL(set_groups); int set_current_groups(struct group_info *group_info) { struct cred *new; + struct cred *old; new = prepare_creds(); if (!new) return -ENOMEM; + old = current_cred(); + set_groups(new, group_info); + + retval = security_task_fix_setgroups(new, old); + if (retval < 0) + goto error; + return commit_creds(new); + +error: + abort_creds(new); + return retval; } EXPORT_SYMBOL(set_current_groups); diff --git a/security/security.c b/security/security.c index b7cf5cbfdc67..eaed8d16d90a 100644 --- a/security/security.c +++ b/security/security.c @@ -1809,6 +1809,11 @@ int security_task_fix_setgid(struct cred *new, const struct cred *old, return call_int_hook(task_fix_setgid, 0, new, old, flags); } +int security_task_fix_setgroups(struct cred *new, const struct cred *old) +{ + return call_int_hook(task_fix_setgroups, 0, new, old); +} + int security_task_setpgid(struct task_struct *p, pid_t pgid) { return call_int_hook(task_setpgid, 0, p, pgid); -- 2.36.1.476.g0c4daa206d-goog
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