From 2fd895842d49c23137ae48252dd211e5d6d8a3ed Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 17 Jul 2025 08:43:43 +0100 Subject: rxrpc: Fix notification vs call-release vs recvmsg When a call is released, rxrpc takes the spinlock and removes it from ->recvmsg_q in an effort to prevent racing recvmsg() invocations from seeing the same call. Now, rxrpc_recvmsg() only takes the spinlock when actually removing a call from the queue; it doesn't, however, take it in the lead up to that when it checks to see if the queue is empty. It *does* hold the socket lock, which prevents a recvmsg/recvmsg race - but this doesn't prevent sendmsg from ending the call because sendmsg() drops the socket lock and relies on the call->user_mutex. Fix this by firstly removing the bit in rxrpc_release_call() that dequeues the released call and, instead, rely on recvmsg() to simply discard released calls (done in a preceding fix). Secondly, rxrpc_notify_socket() is abandoned if the call is already marked as released rather than trying to be clever by setting both pointers in call->recvmsg_link to NULL to trick list_empty(). This isn't perfect and can still race, resulting in a released call on the queue, but recvmsg() will now clean that up. Fixes: 17926a79320a ("[AF_RXRPC]: Provide secure RxRPC sockets for use by userspace and kernel both") Signed-off-by: David Howells Reviewed-by: Jeffrey Altman cc: Marc Dionne cc: Junvyyang, Tencent Zhuque Lab cc: LePremierHomme cc: Simon Horman cc: linux-afs@lists.infradead.org Link: https://patch.msgid.link/20250717074350.3767366-4-dhowells@redhat.com Signed-off-by: Jakub Kicinski --- include/trace/events/rxrpc.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/trace/events/rxrpc.h b/include/trace/events/rxrpc.h index e7dcfb1369b6..de6f6d25767c 100644 --- a/include/trace/events/rxrpc.h +++ b/include/trace/events/rxrpc.h @@ -322,10 +322,10 @@ EM(rxrpc_call_put_kernel, "PUT kernel ") \ EM(rxrpc_call_put_poke, "PUT poke ") \ EM(rxrpc_call_put_recvmsg, "PUT recvmsg ") \ + EM(rxrpc_call_put_release_recvmsg_q, "PUT rls-rcmq") \ EM(rxrpc_call_put_release_sock, "PUT rls-sock") \ EM(rxrpc_call_put_release_sock_tba, "PUT rls-sk-a") \ EM(rxrpc_call_put_sendmsg, "PUT sendmsg ") \ - EM(rxrpc_call_put_unnotify, "PUT unnotify") \ EM(rxrpc_call_put_userid_exists, "PUT u-exists") \ EM(rxrpc_call_put_userid, "PUT user-id ") \ EM(rxrpc_call_see_accept, "SEE accept ") \ @@ -338,6 +338,7 @@ EM(rxrpc_call_see_disconnected, "SEE disconn ") \ EM(rxrpc_call_see_distribute_error, "SEE dist-err") \ EM(rxrpc_call_see_input, "SEE input ") \ + EM(rxrpc_call_see_notify_released, "SEE nfy-rlsd") \ EM(rxrpc_call_see_recvmsg, "SEE recvmsg ") \ EM(rxrpc_call_see_release, "SEE release ") \ EM(rxrpc_call_see_userid_exists, "SEE u-exists") \ -- cgit v1.2.3