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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 <aquini@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Greg Thelen <gthelen@google.com>
Reviewed-by: Davidlohr Bueso <davidlohr@hp.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Rafael Aquini
2014-01-27 17:07:01 -08:00
committed by Linus Torvalds
parent 78f5009cc3
commit 0f3d2b0135
4 changed files with 41 additions and 19 deletions
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7
ipc/msg.c
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@@ -696,7 +696,7 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
goto out_unlock0;
/* raced with RMID? */
if (msq->q_perm.deleted) {
if (!ipc_valid_object(&msq->q_perm)) {
err = -EIDRM;
goto out_unlock0;
}
@@ -731,7 +731,8 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
ipc_lock_object(&msq->q_perm);
ipc_rcu_putref(msq, ipc_rcu_free);
if (msq->q_perm.deleted) {
/* raced with RMID? */
if (!ipc_valid_object(&msq->q_perm)) {
err = -EIDRM;
goto out_unlock0;
}
@@ -909,7 +910,7 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgfl
ipc_lock_object(&msq->q_perm);
/* raced with RMID? */
if (msq->q_perm.deleted) {
if (!ipc_valid_object(&msq->q_perm)) {
msg = ERR_PTR(-EIDRM);
goto out_unlock0;
}