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authorEric Dumazet <edumazet@google.com>2021-06-10 07:27:37 -0700
committerDavid S. Miller <davem@davemloft.net>2021-06-10 14:12:54 -0700
commitf13ef10059ccf5f4ed201cd050176df62ec25bb8 (patch)
tree132e6d50863c18300c45a613dcced47ae166dbd6
parent172947ac678e426cc8eb0e4107017d1fb38c6037 (diff)
net: annotate data race in sock_error()
sock_error() is known to be racy. The code avoids an atomic operation is sk_err is zero, and this field could be changed under us, this is fine. Sysbot reported: BUG: KCSAN: data-race in sock_alloc_send_pskb / unix_release_sock write to 0xffff888131855630 of 4 bytes by task 9365 on cpu 1: unix_release_sock+0x2e9/0x6e0 net/unix/af_unix.c:550 unix_release+0x2f/0x50 net/unix/af_unix.c:859 __sock_release net/socket.c:599 [inline] sock_close+0x6c/0x150 net/socket.c:1258 __fput+0x25b/0x4e0 fs/file_table.c:280 ____fput+0x11/0x20 fs/file_table.c:313 task_work_run+0xae/0x130 kernel/task_work.c:164 tracehook_notify_resume include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop kernel/entry/common.c:174 [inline] exit_to_user_mode_prepare+0x156/0x190 kernel/entry/common.c:208 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline] syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:301 do_syscall_64+0x56/0x90 arch/x86/entry/common.c:57 entry_SYSCALL_64_after_hwframe+0x44/0xae read to 0xffff888131855630 of 4 bytes by task 9385 on cpu 0: sock_error include/net/sock.h:2269 [inline] sock_alloc_send_pskb+0xe4/0x4e0 net/core/sock.c:2336 unix_dgram_sendmsg+0x478/0x1610 net/unix/af_unix.c:1671 unix_seqpacket_sendmsg+0xc2/0x100 net/unix/af_unix.c:2055 sock_sendmsg_nosec net/socket.c:654 [inline] sock_sendmsg net/socket.c:674 [inline] ____sys_sendmsg+0x360/0x4d0 net/socket.c:2350 __sys_sendmsg_sock+0x25/0x30 net/socket.c:2416 io_sendmsg fs/io_uring.c:4367 [inline] io_issue_sqe+0x231a/0x6750 fs/io_uring.c:6135 __io_queue_sqe+0xe9/0x360 fs/io_uring.c:6414 __io_req_task_submit fs/io_uring.c:2039 [inline] io_async_task_func+0x312/0x590 fs/io_uring.c:5074 __tctx_task_work fs/io_uring.c:1910 [inline] tctx_task_work+0x1d4/0x3d0 fs/io_uring.c:1924 task_work_run+0xae/0x130 kernel/task_work.c:164 tracehook_notify_signal include/linux/tracehook.h:212 [inline] handle_signal_work kernel/entry/common.c:145 [inline] exit_to_user_mode_loop kernel/entry/common.c:171 [inline] exit_to_user_mode_prepare+0xf8/0x190 kernel/entry/common.c:208 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline] syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:301 do_syscall_64+0x56/0x90 arch/x86/entry/common.c:57 entry_SYSCALL_64_after_hwframe+0x44/0xae value changed: 0x00000000 -> 0x00000068 Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 9385 Comm: syz-executor.3 Not tainted 5.13.0-rc4-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--include/net/sock.h7
1 files changed, 6 insertions, 1 deletions
diff --git a/include/net/sock.h b/include/net/sock.h
index 0e962d8bc73b..2fc513aa114c 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2266,8 +2266,13 @@ struct sk_buff *sock_dequeue_err_skb(struct sock *sk);
static inline int sock_error(struct sock *sk)
{
int err;
- if (likely(!sk->sk_err))
+
+ /* Avoid an atomic operation for the common case.
+ * This is racy since another cpu/thread can change sk_err under us.
+ */
+ if (likely(data_race(!sk->sk_err)))
return 0;
+
err = xchg(&sk->sk_err, 0);
return -err;
}