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ipc: introduce ipc_valid_object() helper to sort out IPC_RMID races

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After the locking semantics for the SysV IPC API got improved, a couple
of IPC_RMID race windows were opened because we ended up dropping the
'kern_ipc_perm.deleted' check performed way down in ipc_lock().  The
spotted races got sorted out by re-introducing the old test within the
racy critical sections.

This patch introduces ipc_valid_object() to consolidate the way we cope
with IPC_RMID races by using the same abstraction across the API
implementation.

Signed-off-by: Rafael Aquini <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Acked-by: Greg Thelen <[email protected]>
Reviewed-by: Davidlohr Bueso <[email protected]>
Cc: Manfred Spraul <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Rafael Aquini 2014-01-27 17:07:01 -08:00 • committed by Linus Torvalds
commit 0f3d2b0135
4 changed files with 41 additions and 19 deletions
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16
ipc/shm.c
View file

@ -975,6 +975,13 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
goto out_unlock1;
ipc_lock_object(&shp->shm_perm);
/* check if shm_destroy() is tearing down shp */
if (!ipc_valid_object(&shp->shm_perm)) {
err = -EIDRM;
goto out_unlock0;
}
if (!ns_capable(ns->user_ns, CAP_IPC_LOCK)) {
kuid_t euid = current_euid();
if (!uid_eq(euid, shp->shm_perm.uid) &&
@ -989,13 +996,6 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
}
shm_file = shp->shm_file;
/* check if shm_destroy() is tearing down shp */
if (shm_file == NULL) {
err = -EIDRM;
goto out_unlock0;
}
if (is_file_hugepages(shm_file))
goto out_unlock0;
@ -1116,7 +1116,7 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
ipc_lock_object(&shp->shm_perm);
/* check if shm_destroy() is tearing down shp */
if (shp->shm_file == NULL) {
if (!ipc_valid_object(&shp->shm_perm)) {
ipc_unlock_object(&shp->shm_perm);
err = -EIDRM;
goto out_unlock;