From: Jesper Nilsson <jesper.nilsson@xxxxxxxx>
Subject: ipc,shm: correct error return value in shmctl (SHM_UNLOCK)
2caacaa82a51b78 ("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@xxxxxxxx>
Cc: Davidlohr Bueso <davidlohr@xxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [3.12.x]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
ipc/shm.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff -puN ipc/shm.c~ipcshm-correct-error-return-value-in-shmctl-shm_unlock ipc/shm.c
--- a/ipc/shm.c~ipcshm-correct-error-return-value-in-shmctl-shm_unlock
+++ a/ipc/shm.c
@@ -977,12 +977,15 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int,
ipc_lock_object(&shp->shm_perm);
if (!ns_capable(ns->user_ns, CAP_IPC_LOCK)) {
kuid_t euid = current_euid();
- err = -EPERM;
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;
- if (cmd == SHM_LOCK && !rlimit(RLIMIT_MEMLOCK))
+ }
+ if (cmd == SHM_LOCK && !rlimit(RLIMIT_MEMLOCK)) {
+ err = -EPERM;
goto out_unlock0;
+ }
}
shm_file = shp->shm_file;
_
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