Inside the loop in rxrpc_wait_to_be_connected() it checks call->error to
see if it should exit the loop without first checking the call state. This
is probably safe as if call->error is set, the call is dead anyway, but we
should probably wait for the call state to have been set to completion
first, lest it cause surprise on the way out.
Fix this by only accessing call->error if the call is complete. We don't
actually need to access the error inside the loop as we'll do that after.
This caused the following report:
BUG: KCSAN: data-race in rxrpc_send_data / rxrpc_set_call_completion
write to 0xffff888159cf3c50 of 4 bytes by task 25673 on cpu 1:
rxrpc_set_call_completion+0x71/0x1c0 net/rxrpc/call_state.c:22
rxrpc_send_data_packet+0xba9/0x1650 net/rxrpc/output.c:479
rxrpc_transmit_one+0x1e/0x130 net/rxrpc/output.c:714
rxrpc_decant_prepared_tx net/rxrpc/call_event.c:326 [inline]
rxrpc_transmit_some_data+0x496/0x600 net/rxrpc/call_event.c:350
rxrpc_input_call_event+0x564/0x1220 net/rxrpc/call_event.c:464
rxrpc_io_thread+0x307/0x1d80 net/rxrpc/io_thread.c:461
kthread+0x1ac/0x1e0 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
read to 0xffff888159cf3c50 of 4 bytes by task 25672 on cpu 0:
rxrpc_send_data+0x29e/0x1950 net/rxrpc/sendmsg.c:296
rxrpc_do_sendmsg+0xb7a/0xc20 net/rxrpc/sendmsg.c:726
rxrpc_sendmsg+0x413/0x520 net/rxrpc/af_rxrpc.c:565
sock_sendmsg_nosec net/socket.c:724 [inline]
sock_sendmsg net/socket.c:747 [inline]
____sys_sendmsg+0x375/0x4c0 net/socket.c:2501
___sys_sendmsg net/socket.c:2555 [inline]
__sys_sendmmsg+0x263/0x500 net/socket.c:2641
__do_sys_sendmmsg net/socket.c:2670 [inline]
__se_sys_sendmmsg net/socket.c:2667 [inline]
__x64_sys_sendmmsg+0x57/0x60 net/socket.c:2667
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
value changed: 0x00000000 -> 0xffffffea
Fixes: 9d35d880e0e4 ("rxrpc: Move client call connection to the I/O thread")
Reported-by: [email protected]
Link: https://lore.kernel.org/r/[email protected]/
Signed-off-by: David Howells <[email protected]>
cc: Marc Dionne <[email protected]>
cc: Dmitry Vyukov <[email protected]>
cc: "David S. Miller" <[email protected]>
cc: Eric Dumazet <[email protected]>
cc: Jakub Kicinski <[email protected]>
cc: Paolo Abeni <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
---
net/rxrpc/sendmsg.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/net/rxrpc/sendmsg.c b/net/rxrpc/sendmsg.c
index da49fcf1c456..6caa47d352ed 100644
--- a/net/rxrpc/sendmsg.c
+++ b/net/rxrpc/sendmsg.c
@@ -50,15 +50,11 @@ static int rxrpc_wait_to_be_connected(struct rxrpc_call *call, long *timeo)
_enter("%d", call->debug_id);
if (rxrpc_call_state(call) != RXRPC_CALL_CLIENT_AWAIT_CONN)
- return call->error;
+ goto no_wait;
add_wait_queue_exclusive(&call->waitq, &myself);
for (;;) {
- ret = call->error;
- if (ret < 0)
- break;
-
switch (call->interruptibility) {
case RXRPC_INTERRUPTIBLE:
case RXRPC_PREINTERRUPTIBLE:
@@ -69,10 +65,9 @@ static int rxrpc_wait_to_be_connected(struct rxrpc_call *call, long *timeo)
set_current_state(TASK_UNINTERRUPTIBLE);
break;
}
- if (rxrpc_call_state(call) != RXRPC_CALL_CLIENT_AWAIT_CONN) {
- ret = call->error;
+
+ if (rxrpc_call_state(call) != RXRPC_CALL_CLIENT_AWAIT_CONN)
break;
- }
if ((call->interruptibility == RXRPC_INTERRUPTIBLE ||
call->interruptibility == RXRPC_PREINTERRUPTIBLE) &&
signal_pending(current)) {
@@ -85,6 +80,7 @@ static int rxrpc_wait_to_be_connected(struct rxrpc_call *call, long *timeo)
remove_wait_queue(&call->waitq, &myself);
__set_current_state(TASK_RUNNING);
+no_wait:
if (ret == 0 && rxrpc_call_is_complete(call))
ret = call->error;
Hello:
This patch was applied to netdev/net.git (main)
by Paolo Abeni <[email protected]>:
On Tue, 25 Apr 2023 13:56:35 +0100 you wrote:
> Inside the loop in rxrpc_wait_to_be_connected() it checks call->error to
> see if it should exit the loop without first checking the call state. This
> is probably safe as if call->error is set, the call is dead anyway, but we
> should probably wait for the call state to have been set to completion
> first, lest it cause surprise on the way out.
>
> Fix this by only accessing call->error if the call is complete. We don't
> actually need to access the error inside the loop as we'll do that after.
>
> [...]
Here is the summary with links:
- [net] rxrpc: Fix potential data race in rxrpc_wait_to_be_connected()
https://git.kernel.org/netdev/net/c/2b5fdc0f5caa
You are awesome, thank you!
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