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ipc,shm: correct error return value in shmctl (SHM_UNLOCK)

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Commit 2caacaa82a ("ipc,shm: shorten critical region for shmctl")
restructured the ipc shm to shorten critical region, but introduced a
path where the return value could be -EPERM, even if the operation
actually was performed.

Before the commit, the err return value was reset by the return value
from security_shm_shmctl() after the if (!ns_capable(...)) statement.

Now, we still exit the if statement with err set to -EPERM, and in the
case of SHM_UNLOCK, it is not reset at all, and used as the return value
from shmctl.

To fix this, we only set err when errors occur, leaving the fallthrough
case alone.

Signed-off-by: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: <stable@vger.kernel.org>	[3.12.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jesper Nilsson 2013-11-21 14:32:08 -08:00 committed by Linus Torvalds
parent b7a9f420ed
commit 3a72660b07
1 changed files with 6 additions and 3 deletions
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9
ipc/shm.c
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@ -977,12 +977,15 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
ipc_lock_object(&shp->shm_perm); ipc_lock_object(&shp->shm_perm);
if (!ns_capable(ns->user_ns, CAP_IPC_LOCK)) { if (!ns_capable(ns->user_ns, CAP_IPC_LOCK)) {
kuid_t euid = current_euid(); kuid_t euid = current_euid();
err = -EPERM;
if (!uid_eq(euid, shp->shm_perm.uid) && if (!uid_eq(euid, shp->shm_perm.uid) &&
!uid_eq(euid, shp->shm_perm.cuid)) !uid_eq(euid, shp->shm_perm.cuid)) {
err = -EPERM;
goto out_unlock0; goto out_unlock0;
if (cmd == SHM_LOCK && !rlimit(RLIMIT_MEMLOCK)) }
if (cmd == SHM_LOCK && !rlimit(RLIMIT_MEMLOCK)) {
err = -EPERM;
goto out_unlock0; goto out_unlock0;
}
} }
shm_file = shp->shm_file; shm_file = shp->shm_file;