Commit fcfe0ac2 authored by Micah Morton's avatar Micah Morton
Browse files

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. Tested by putting print
statement in security_task_fix_setgroups() hook and confirming that it
gets hit when userspace does a setgroups() syscall.

Acked-by: default avatarCasey Schaufler <casey@schaufler-ca.com>
Reviewed-by: default avatarSerge Hallyn <serge@hallyn.com>
Signed-off-by: default avatarMicah Morton <mortonm@chromium.org>
parent a1732d68

include/linux/lsm_hook_defs.h

+1 −0
Original line number Diff line number Diff line
@@ -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)

include/linux/lsm_hooks.h

+7 −0
Original line number Diff line number Diff line
@@ -702,6 +702,13 @@ 
 *	@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.

include/linux/security.h

+7 −0
Original line number Diff line number Diff line
@@ -415,6 +415,7 @@ 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);
@@ -1098,6 +1099,12 @@ 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;

kernel/groups.c

+13 −0
Original line number Diff line number Diff line
@@ -134,13 +134,26 @@ EXPORT_SYMBOL(set_groups); 
int set_current_groups(struct group_info *group_info)

{

	struct cred *new;

	const struct cred *old;

	int retval;



	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);

security/security.c

+5 −0
Original line number Diff line number Diff line
@@ -1803,6 +1803,11 @@ 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);