From: Kuniyuki Iwashima kuniyu@amazon.com
[ 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@googlegroups.com Signed-off-by: Kuniyuki Iwashima kuniyu@amazon.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/unix/af_unix.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)
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) {