From: Cong Wang <xiyou.wangcong@gmail.com>
To: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, geneblue.mail@gmail.com,
Cong Wang <xiyou.wangcong@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Manfred Spraul <manfred@colorfullife.com>
Subject: [Patch] mqueue: fix the retry logic for netlink_attachskb()
Date: Fri, 7 Jul 2017 11:32:15 -0700 [thread overview]
Message-ID: <1499452335-3478-1-git-send-email-xiyou.wangcong@gmail.com> (raw)
The retry logic for netlink_attachskb() inside sys_mq_notify()
is suspicious and vulnerable:
1) The sock refcnt is already released when retry is needed
2) The fd is controllable by user-space because we already
release the file refcnt
so we when retry and the fd has been closed during this small
window, we end up calling netlink_detachskb() on the error path
which releases the sock again and could lead to a use-after-free.
We don't need to re-get the file pointer in the retry loop, keep
it until we finally succeed.
Reported-by: GeneBlue <geneblue.mail@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
---
ipc/mqueue.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index e8d41ff..b894d6c 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -1237,15 +1237,15 @@ SYSCALL_DEFINE2(mq_notify, mqd_t, mqdes,
/* TODO: add a header? */
skb_put(nc, NOTIFY_COOKIE_LEN);
/* and attach it to the socket */
-retry:
f = fdget(notification.sigev_signo);
if (!f.file) {
ret = -EBADF;
goto out;
}
+retry:
sock = netlink_getsockbyfilp(f.file);
- fdput(f);
if (IS_ERR(sock)) {
+ fdput(f);
ret = PTR_ERR(sock);
sock = NULL;
goto out;
@@ -1255,6 +1255,7 @@ SYSCALL_DEFINE2(mq_notify, mqd_t, mqdes,
ret = netlink_attachskb(sock, nc, &timeo, NULL);
if (ret == 1)
goto retry;
+ fdput(f);
if (ret) {
sock = NULL;
nc = NULL;
--
2.5.5
next reply other threads:[~2017-07-07 18:32 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-07 18:32 Cong Wang [this message]
2017-07-08 0:23 ` [Patch] mqueue: fix the retry logic for netlink_attachskb() Linus Torvalds
2017-07-08 18:04 ` Cong Wang
2017-07-08 18:55 ` Linus Torvalds
2017-07-09 19:57 ` Cong Wang
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