This is a note to let you know that I've just added the patch titled
af_unix: Fix memory leaks of the whole sk due to OOB skb.
to the 6.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
af_unix-fix-memory-leaks-of-the-whole-sk-due-to-oob-.patch
and it can be found in the queue-6.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit f41b8eed4fa9bce8ea1665901fcc3be75deabb81
Author: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Date: Thu Sep 29 08:52:04 2022 -0700
af_unix: Fix memory leaks of the whole sk due to OOB skb.
[ Upstream commit 7a62ed61367b8fd01bae1e18e30602c25060d824 ]
syzbot reported a sequence of memory leaks, and one of them indicated we
failed to free a whole sk:
unreferenced object 0xffff8880126e0000 (size 1088):
comm "syz-executor419", pid 326, jiffies 4294773607 (age 12.609s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 7d 00 00 00 00 00 00 00 ........}.......
01 00 07 40 00 00 00 00 00 00 00 00 00 00 00 00 ...@............
backtrace:
[<000000006fefe750>] sk_prot_alloc+0x64/0x2a0 net/core/sock.c:1970
[<0000000074006db5>] sk_alloc+0x3b/0x800 net/core/sock.c:2029
[<00000000728cd434>] unix_create1+0xaf/0x920 net/unix/af_unix.c:928
[<00000000a279a139>] unix_create+0x113/0x1d0 net/unix/af_unix.c:997
[<0000000068259812>] __sock_create+0x2ab/0x550 net/socket.c:1516
[<00000000da1521e1>] sock_create net/socket.c:1566 [inline]
[<00000000da1521e1>] __sys_socketpair+0x1a8/0x550 net/socket.c:1698
[<000000007ab259e1>] __do_sys_socketpair net/socket.c:1751 [inline]
[<000000007ab259e1>] __se_sys_socketpair net/socket.c:1748 [inline]
[<000000007ab259e1>] __x64_sys_socketpair+0x97/0x100 net/socket.c:1748
[<000000007dedddc1>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
[<000000007dedddc1>] do_syscall_64+0x38/0x90 arch/x86/entry/common.c:80
[<000000009456679f>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
We can reproduce this issue by creating two AF_UNIX SOCK_STREAM sockets,
send()ing an OOB skb to each other, and close()ing them without consuming
the OOB skbs.
int skpair[2];
socketpair(AF_UNIX, SOCK_STREAM, 0, skpair);
send(skpair[0], "x", 1, MSG_OOB);
send(skpair[1], "x", 1, MSG_OOB);
close(skpair[0]);
close(skpair[1]);
Currently, we free an OOB skb in unix_sock_destructor() which is called via
__sk_free(), but it's too late because the receiver's unix_sk(sk)->oob_skb
is accounted against the sender's sk->sk_wmem_alloc and __sk_free() is
called only when sk->sk_wmem_alloc is 0.
In the repro sequences, we do not consume the OOB skb, so both two sk's
sock_put() never reach __sk_free() due to the positive sk->sk_wmem_alloc.
Then, no one can consume the OOB skb nor call __sk_free(), and we finally
leak the two whole sk.
Thus, we must free the unconsumed OOB skb earlier when close()ing the
socket.
Fixes: 314001f0bf92 ("af_unix: Add OOB support")
Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index bf338b782fc4..d686804119c9 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -569,12 +569,6 @@ static void unix_sock_destructor(struct sock *sk)
skb_queue_purge(&sk->sk_receive_queue);
-#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
- if (u->oob_skb) {
- kfree_skb(u->oob_skb);
- u->oob_skb = NULL;
- }
-#endif
DEBUG_NET_WARN_ON_ONCE(refcount_read(&sk->sk_wmem_alloc));
DEBUG_NET_WARN_ON_ONCE(!sk_unhashed(sk));
DEBUG_NET_WARN_ON_ONCE(sk->sk_socket);
@@ -620,6 +614,13 @@ static void unix_release_sock(struct sock *sk, int embrion)
unix_state_unlock(sk);
+#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
+ if (u->oob_skb) {
+ kfree_skb(u->oob_skb);
+ u->oob_skb = NULL;
+ }
+#endif
+
wake_up_interruptible_all(&u->peer_wait);
if (skpair != NULL) {
