From: Duoming Zhou duoming@zju.edu.cn
[ Upstream commit 7781607938c8371d4c2b243527430241c62e39c2 ]
When the link layer is terminating, x25->neighbour will be set to NULL in x25_disconnect(). As a result, it could cause null-ptr-deref bugs in x25_sendmsg(),x25_recvmsg() and x25_connect(). One of the bugs is shown below.
(Thread 1) | (Thread 2) x25_link_terminated() | x25_recvmsg() x25_kill_by_neigh() | ... x25_disconnect() | lock_sock(sk) ... | ... x25->neighbour = NULL //(1) | ... | x25->neighbour->extended //(2)
The code sets NULL to x25->neighbour in position (1) and dereferences x25->neighbour in position (2), which could cause null-ptr-deref bug.
This patch adds lock_sock() in x25_kill_by_neigh() in order to synchronize with x25_sendmsg(), x25_recvmsg() and x25_connect(). What`s more, the sock held by lock_sock() is not NULL, because it is extracted from x25_list and uses x25_list_lock to synchronize.
Fixes: 4becb7ee5b3d ("net/x25: Fix x25_neigh refcnt leak when x25 disconnect") Signed-off-by: Duoming Zhou duoming@zju.edu.cn Reviewed-by: Lin Ma linma@zju.edu.cn Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/x25/af_x25.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c index 3583354a7d7f..3a171828638b 100644 --- a/net/x25/af_x25.c +++ b/net/x25/af_x25.c @@ -1765,10 +1765,15 @@ void x25_kill_by_neigh(struct x25_neigh *nb)
write_lock_bh(&x25_list_lock);
- sk_for_each(s, &x25_list) - if (x25_sk(s)->neighbour == nb) + sk_for_each(s, &x25_list) { + if (x25_sk(s)->neighbour == nb) { + write_unlock_bh(&x25_list_lock); + lock_sock(s); x25_disconnect(s, ENETUNREACH, 0, 0); - + release_sock(s); + write_lock_bh(&x25_list_lock); + } + } write_unlock_bh(&x25_list_lock);
/* Remove any related forwards */