Messages in this thread Patch in this message | | | From | Davidlohr Bueso <> | Subject | [PATCH 4/5] ipc/msg: Lockless security checks for msgsnd | Date | Thu, 28 Jul 2016 16:33:38 -0700 |
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Just as with msgrcv (along with the rest of sysvipc since a few years ago), perform the security checks without holding the ipc object lock. This also reduces the hogging of the lock for the entire duration of a sender, as we drop the lock upon every iteration -- and this is exactly why we also check for racing with RMID in the first place.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de> --- ipc/msg.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/ipc/msg.c b/ipc/msg.c index 5181259e2ff0..fe793304dddb 100644 --- a/ipc/msg.c +++ b/ipc/msg.c @@ -623,14 +623,14 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext, goto out_unlock1; } - ipc_lock_object(&msq->q_perm); - for (;;) { struct msg_sender s; err = -EACCES; if (ipcperms(ns, &msq->q_perm, S_IWUGO)) - goto out_unlock0; + goto out_unlock1; + + ipc_lock_object(&msq->q_perm); /* raced with RMID? */ if (!ipc_valid_object(&msq->q_perm)) { @@ -681,6 +681,7 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext, goto out_unlock0; } + ipc_unlock_object(&msq->q_perm); } msq->q_lspid = task_tgid_vnr(current); msq->q_stime = get_seconds(); -- 2.6.6
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