4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Gavrilov Ilia <Ilia.Gavrilov@xxxxxxxxxxx>
[ Upstream commit 0b9130247f3b6a1122478471ff0e014ea96bb735 ]
syzbot reported a memory leak in nr_create() [0].
Commit 409db27e3a2e ("netrom: Fix use-after-free of a listening socket.")
added sock_hold() to the nr_heartbeat_expiry() function, where
a) a socket has a SOCK_DESTROY flag or
b) a listening socket has a SOCK_DEAD flag.
But in the case "a," when the SOCK_DESTROY flag is set, the file descriptor
has already been closed and the nr_release() function has been called.
So it makes no sense to hold the reference count because no one will
call another nr_destroy_socket() and put it as in the case "b."
nr_connect
nr_establish_data_link
nr_start_heartbeat
nr_release
switch (nr->state)
case NR_STATE_3
nr->state = NR_STATE_2
sock_set_flag(sk, SOCK_DESTROY);
nr_rx_frame
nr_process_rx_frame
switch (nr->state)
case NR_STATE_2
nr_state2_machine()
nr_disconnect()
nr_sk(sk)->state = NR_STATE_0
sock_set_flag(sk, SOCK_DEAD)
nr_heartbeat_expiry
switch (nr->state)
case NR_STATE_0
if (sock_flag(sk, SOCK_DESTROY) ||
(sk->sk_state == TCP_LISTEN
&& sock_flag(sk, SOCK_DEAD)))
sock_hold() // ( !!! )
nr_destroy_socket()
To fix the memory leak, let's call sock_hold() only for a listening socket.
Found by InfoTeCS on behalf of Linux Verification Center
(linuxtesting.org) with Syzkaller.
[0]: https://syzkaller.appspot.com/bug?extid=d327a1f3b12e1e206c16
Reported-by: syzbot+d327a1f3b12e1e206c16@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=d327a1f3b12e1e206c16
Fixes: 409db27e3a2e ("netrom: Fix use-after-free of a listening socket.")
Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/netrom/nr_timer.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/netrom/nr_timer.c b/net/netrom/nr_timer.c
index 2bf99bd5be58c..67d012e0badeb 100644
--- a/net/netrom/nr_timer.c
+++ b/net/netrom/nr_timer.c
@@ -124,7 +124,8 @@ static void nr_heartbeat_expiry(struct timer_list *t)
is accepted() it isn't 'dead' so doesn't get removed. */
if (sock_flag(sk, SOCK_DESTROY) ||
(sk->sk_state == TCP_LISTEN && sock_flag(sk, SOCK_DEAD))) {
- sock_hold(sk);
+ if (sk->sk_state == TCP_LISTEN)
+ sock_hold(sk);
bh_unlock_sock(sk);
nr_destroy_socket(sk);
goto out;
--
2.43.0
