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authorPeilin Ye2022-08-08 11:04:47 -0700
committerDavid S. Miller2022-08-10 09:50:18 +0100
commit7e97cfed9929eaabc41829c395eb0d1350fccb9d (patch)
tree071ee789d5405db1155b1518329e519607f2c620 /net
parent6fd2c17fb6e02a8c0ab51df1cfec82ce96b8e83d (diff)
vsock: Fix memory leak in vsock_connect()
An O_NONBLOCK vsock_connect() request may try to reschedule @connect_work. Imagine the following sequence of vsock_connect() requests: 1. The 1st, non-blocking request schedules @connect_work, which will expire after 200 jiffies. Socket state is now SS_CONNECTING; 2. Later, the 2nd, blocking request gets interrupted by a signal after a few jiffies while waiting for the connection to be established. Socket state is back to SS_UNCONNECTED, but @connect_work is still pending, and will expire after 100 jiffies. 3. Now, the 3rd, non-blocking request tries to schedule @connect_work again. Since @connect_work is already scheduled, schedule_delayed_work() silently returns. sock_hold() is called twice, but sock_put() will only be called once in vsock_connect_timeout(), causing a memory leak reported by syzbot: BUG: memory leak unreferenced object 0xffff88810ea56a40 (size 1232): comm "syz-executor756", pid 3604, jiffies 4294947681 (age 12.350s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 28 00 07 40 00 00 00 00 00 00 00 00 00 00 00 00 (..@............ backtrace: [<ffffffff837c830e>] sk_prot_alloc+0x3e/0x1b0 net/core/sock.c:1930 [<ffffffff837cbe22>] sk_alloc+0x32/0x2e0 net/core/sock.c:1989 [<ffffffff842ccf68>] __vsock_create.constprop.0+0x38/0x320 net/vmw_vsock/af_vsock.c:734 [<ffffffff842ce8f1>] vsock_create+0xc1/0x2d0 net/vmw_vsock/af_vsock.c:2203 [<ffffffff837c0cbb>] __sock_create+0x1ab/0x2b0 net/socket.c:1468 [<ffffffff837c3acf>] sock_create net/socket.c:1519 [inline] [<ffffffff837c3acf>] __sys_socket+0x6f/0x140 net/socket.c:1561 [<ffffffff837c3bba>] __do_sys_socket net/socket.c:1570 [inline] [<ffffffff837c3bba>] __se_sys_socket net/socket.c:1568 [inline] [<ffffffff837c3bba>] __x64_sys_socket+0x1a/0x20 net/socket.c:1568 [<ffffffff84512815>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [<ffffffff84512815>] do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80 [<ffffffff84600068>] entry_SYSCALL_64_after_hwframe+0x44/0xae <...> Use mod_delayed_work() instead: if @connect_work is already scheduled, reschedule it, and undo sock_hold() to keep the reference count balanced. Reported-and-tested-by: syzbot+b03f55bf128f9a38f064@syzkaller.appspotmail.com Fixes: d021c344051a ("VSOCK: Introduce VM Sockets") Co-developed-by: Stefano Garzarella <sgarzare@redhat.com> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com> Signed-off-by: Peilin Ye <peilin.ye@bytedance.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/vmw_vsock/af_vsock.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index f04abf662ec6..4d68681f5abe 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1391,7 +1391,14 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr,
* timeout fires.
*/
sock_hold(sk);
- schedule_delayed_work(&vsk->connect_work, timeout);
+
+ /* If the timeout function is already scheduled,
+ * reschedule it, then ungrab the socket refcount to
+ * keep it balanced.
+ */
+ if (mod_delayed_work(system_wq, &vsk->connect_work,
+ timeout))
+ sock_put(sk);
/* Skip ahead to preserve error code set above. */
goto out_wait;