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authorDavidlohr Bueso <dave@stgolabs.net>2018-04-10 16:35:26 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-04-11 10:28:37 -0700
commita280d6dc77eb6002f269d58cd47c7c7e69b617b6 (patch)
tree312545b1f84f43d8cb8aba2168a8ad32eac09cb8 /ipc
parentc21a6970ae727839a2f300cd8dd957de0d0238c3 (diff)
downloadlinux-stericsson-a280d6dc77eb6002f269d58cd47c7c7e69b617b6.tar.gz
ipc/sem: introduce semctl(SEM_STAT_ANY)
There is a permission discrepancy when consulting shm ipc object metadata between /proc/sysvipc/sem (0444) and the SEM_STAT semctl command. The later does permission checks for the object vs S_IRUGO. As such there can be cases where EACCESS is returned via syscall but the info is displayed anyways in the procfs files. While this might have security implications via info leaking (albeit no writing to the sma metadata), this behavior goes way back and showing all the objects regardless of the permissions was most likely an overlook - so we are stuck with it. Furthermore, modifying either the syscall or the procfs file can cause userspace programs to break (ie ipcs). Some applications require getting the procfs info (without root privileges) and can be rather slow in comparison with a syscall -- up to 500x in some reported cases for shm. This patch introduces a new SEM_STAT_ANY command such that the sem ipc object permissions are ignored, and only audited instead. In addition, I've left the lsm security hook checks in place, as if some policy can block the call, then the user has no other choice than just parsing the procfs file. Link: http://lkml.kernel.org/r/20180215162458.10059-3-dave@stgolabs.net Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Reported-by: Robert Kettler <robert.kettler@outlook.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Kees Cook <keescook@chromium.org> Cc: Manfred Spraul <manfred@colorfullife.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Michal Hocko <mhocko@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc')
-rw-r--r--ipc/sem.c17
1 files changed, 12 insertions, 5 deletions
diff --git a/ipc/sem.c b/ipc/sem.c
index 2994da8ccc7f..06be75d9217a 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -1220,14 +1220,14 @@ static int semctl_stat(struct ipc_namespace *ns, int semid,
memset(semid64, 0, sizeof(*semid64));
rcu_read_lock();
- if (cmd == SEM_STAT) {
+ if (cmd == SEM_STAT || cmd == SEM_STAT_ANY) {
sma = sem_obtain_object(ns, semid);
if (IS_ERR(sma)) {
err = PTR_ERR(sma);
goto out_unlock;
}
id = sma->sem_perm.id;
- } else {
+ } else { /* IPC_STAT */
sma = sem_obtain_object_check(ns, semid);
if (IS_ERR(sma)) {
err = PTR_ERR(sma);
@@ -1235,9 +1235,14 @@ static int semctl_stat(struct ipc_namespace *ns, int semid,
}
}
- err = -EACCES;
- if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
- goto out_unlock;
+ /* see comment for SHM_STAT_ANY */
+ if (cmd == SEM_STAT_ANY)
+ audit_ipc_obj(&sma->sem_perm);
+ else {
+ err = -EACCES;
+ if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
+ goto out_unlock;
+ }
err = security_sem_semctl(&sma->sem_perm, cmd);
if (err)
@@ -1626,6 +1631,7 @@ long ksys_semctl(int semid, int semnum, int cmd, unsigned long arg)
return semctl_info(ns, semid, cmd, p);
case IPC_STAT:
case SEM_STAT:
+ case SEM_STAT_ANY:
err = semctl_stat(ns, semid, cmd, &semid64);
if (err < 0)
return err;
@@ -1732,6 +1738,7 @@ long compat_ksys_semctl(int semid, int semnum, int cmd, int arg)
return semctl_info(ns, semid, cmd, p);
case IPC_STAT:
case SEM_STAT:
+ case SEM_STAT_ANY:
err = semctl_stat(ns, semid, cmd, &semid64);
if (err < 0)
return err;