Commit 2caacaa82a51b78fc0c800e206473874094287ed 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.nils...@axis.com> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Davidlohr Bueso <davidl...@hp.com> Cc: Rik van Riel <r...@redhat.com> Cc: Michel Lespinasse <wal...@google.com> Cc: Al Viro <v...@zeniv.linux.org.uk> Cc: sta...@vger.kernel.org --- ipc/shm.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/ipc/shm.c b/ipc/shm.c index d697396..4076f9e 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -974,12 +974,15 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf) 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; -- 1.8.4 /^JN - Jesper Nilsson -- Jesper Nilsson -- jesper.nils...@axis.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/