rxrpc: Fix recvmsg() unconditional requeue

If rxrpc_recvmsg() fails because MSG_DONTWAIT was specified but the call at
the front of the recvmsg queue already has its mutex locked, it requeues
the call - whether or not the call is already queued.  The call may be on
the queue because MSG_PEEK was also passed and so the call was not dequeued
or because the I/O thread requeued it.

The unconditional requeue may then corrupt the recvmsg queue, leading to
things like UAFs or refcount underruns.

Fix this by only requeuing the call if it isn't already on the queue - and
moving it to the front if it is already queued.  If we don't queue it, we
have to put the ref we obtained by dequeuing it.

Also, MSG_PEEK doesn't dequeue the call so shouldn't call
rxrpc_notify_socket() for the call if we didn't use up all the data on the
queue, so fix that also.

Fixes: 540b1c48c37a ("rxrpc: Fix deadlock between call creation and sendmsg/recvmsg")
Reported-by: Faith <faith@zellic.io>
Reported-by: Pumpkin Chang <pumpkin@devco.re>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Marc Dionne <marc.dionne@auristor.com>
cc: Nir Ohfeld <niro@wiz.io>
cc: Willy Tarreau <w@1wt.eu>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: stable@kernel.org
Link: https://patch.msgid.link/95163.1768428203@warthog.procyon.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/trace/events/rxrpc.h b/include/trace/events/rxrpc.h
index de6f6d25767c6e240ebba89c051e6cc1194d09a2..869f97c9bf733e48ed69b038e3f592a5a3a0ff7f 100644 (file)
--- a/include/trace/events/rxrpc.h
+++ b/include/trace/events/rxrpc.h
@@ -322,6 +322,7 @@
        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_recvmsg_peek_nowait,  "PUT peek-nwt") \
        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") \
@@ -340,6 +341,9 @@
        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_recvmsg_requeue,      "SEE recv-rqu") \
+       EM(rxrpc_call_see_recvmsg_requeue_first, "SEE recv-rqF") \
+       EM(rxrpc_call_see_recvmsg_requeue_move, "SEE recv-rqM") \
        EM(rxrpc_call_see_release,              "SEE release ") \
        EM(rxrpc_call_see_userid_exists,        "SEE u-exists") \
        EM(rxrpc_call_see_waiting_call,         "SEE q-conn  ") \

diff --git a/net/rxrpc/recvmsg.c b/net/rxrpc/recvmsg.c
index 7fa7e77f6bb9907cae26f5444e845c561ef5b2a7..e1f7513a46dbe3ba67ca3638ebb6ad72a7e672f0 100644 (file)
--- a/net/rxrpc/recvmsg.c
+++ b/net/rxrpc/recvmsg.c
@@ -518,7 +518,8 @@ try_again:
        if (rxrpc_call_has_failed(call))
                goto call_failed;
 
-       if (!skb_queue_empty(&call->recvmsg_queue))
+       if (!(flags & MSG_PEEK) &&
+           !skb_queue_empty(&call->recvmsg_queue))
                rxrpc_notify_socket(call);
        goto not_yet_complete;
 
@@ -549,11 +550,21 @@ error_unlock_call:
 error_requeue_call:
        if (!(flags & MSG_PEEK)) {
                spin_lock_irq(&rx->recvmsg_lock);
-               list_add(&call->recvmsg_link, &rx->recvmsg_q);
-               spin_unlock_irq(&rx->recvmsg_lock);
+               if (list_empty(&call->recvmsg_link)) {
+                       list_add(&call->recvmsg_link, &rx->recvmsg_q);
+                       rxrpc_see_call(call, rxrpc_call_see_recvmsg_requeue);
+                       spin_unlock_irq(&rx->recvmsg_lock);
+               } else if (list_is_first(&call->recvmsg_link, &rx->recvmsg_q)) {
+                       spin_unlock_irq(&rx->recvmsg_lock);
+                       rxrpc_put_call(call, rxrpc_call_see_recvmsg_requeue_first);
+               } else {
+                       list_move(&call->recvmsg_link, &rx->recvmsg_q);
+                       spin_unlock_irq(&rx->recvmsg_lock);
+                       rxrpc_put_call(call, rxrpc_call_see_recvmsg_requeue_move);
+               }
                trace_rxrpc_recvmsg(call_debug_id, rxrpc_recvmsg_requeue, 0);
        } else {
-               rxrpc_put_call(call, rxrpc_call_put_recvmsg);
+               rxrpc_put_call(call, rxrpc_call_put_recvmsg_peek_nowait);
        }
 error_no_call:
        release_sock(&rx->sk);