[net-next 1/1] tipc: fix a potental access after delete in tipc_sk_join()

[net-next 1/1] tipc: fix a potental access after delete in tipc_sk_join()

[Jon Maloy]

In commit d12d2e12cec2 "tipc: send out join messages as soon as new
member is discovered") we added a call to the function tipc_group_join()
without considering the case that the preceding tipc_sk_publish() might
have failed, and the group item already deleted.

We fix this by returning from tipc_sk_join() directly after the
failed tipc_sk_publish.

Reported-by: syzbot+e3eeae78ea88b8d6d858@syzkaller.appspotmail.com
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
---
 net/tipc/socket.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index 1f23627..f38264d 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -2774,6 +2774,7 @@ static int tipc_sk_join(struct tipc_sock *tsk, struct tipc_group_req *mreq)
 	if (rc) {
 		tipc_group_delete(net, grp);
 		tsk->group = NULL;
+		return rc;
 	}
 	/* Eliminate any risk that a broadcast overtakes sent JOINs */
 	tsk->mc_method.rcast = true;
-- 
2.1.4

Re: [net-next 1/1] tipc: fix a potental access after delete in tipc_sk_join()

[David Miller]

From: Jon Maloy <jon.maloy@ericsson.com>
Date: Wed, 10 Jan 2018 21:08:50 +0100

> In commit d12d2e12cec2 "tipc: send out join messages as soon as new
> member is discovered") we added a call to the function tipc_group_join()
> without considering the case that the preceding tipc_sk_publish() might
> have failed, and the group item already deleted.
> 
> We fix this by returning from tipc_sk_join() directly after the
> failed tipc_sk_publish.
> 
> Reported-by: syzbot+e3eeae78ea88b8d6d858@syzkaller.appspotmail.com
> Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>

Applied, thanks Jon.

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