]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
rxrpc: Fix incoming call setup race
authorDavid Howells <dhowells@redhat.com>
Fri, 6 Jan 2023 13:03:18 +0000 (13:03 +0000)
committerDavid Howells <dhowells@redhat.com>
Sat, 7 Jan 2023 09:30:26 +0000 (09:30 +0000)
commit42f229c350f57a8e825f7591e17cbc5c87e50235
treed23e4db2c49fee5670e336e3c25624ee6a5509a9
parent9d35d880e0e4a3ab32d8c12f9e4d76198aadd42d
rxrpc: Fix incoming call setup race

An incoming call can race with rxrpc socket destruction, leading to a
leaked call.  This may result in an oops when the call timer eventually
expires:

   BUG: kernel NULL pointer dereference, address: 0000000000000874
   RIP: 0010:_raw_spin_lock_irqsave+0x2a/0x50
   Call Trace:
    <IRQ>
    try_to_wake_up+0x59/0x550
    ? __local_bh_enable_ip+0x37/0x80
    ? rxrpc_poke_call+0x52/0x110 [rxrpc]
    ? rxrpc_poke_call+0x110/0x110 [rxrpc]
    ? rxrpc_poke_call+0x110/0x110 [rxrpc]
    call_timer_fn+0x24/0x120

with a warning in the kernel log looking something like:

   rxrpc: Call 00000000ba5e571a still in use (1,SvAwtACK,1061d,0)!

incurred during rmmod of rxrpc.  The 1061d is the call flags:

   RECVMSG_READ_ALL, RX_HEARD, BEGAN_RX_TIMER, RX_LAST, EXPOSED,
   IS_SERVICE, RELEASED

but no DISCONNECTED flag (0x800), so it's an incoming (service) call and
it's still connected.

The race appears to be that:

 (1) rxrpc_new_incoming_call() consults the service struct, checks sk_state
     and allocates a call - then pauses, possibly for an interrupt.

 (2) rxrpc_release_sock() sets RXRPC_CLOSE, nulls the service pointer,
     discards the prealloc and releases all calls attached to the socket.

 (3) rxrpc_new_incoming_call() resumes, launching the new call, including
     its timer and attaching it to the socket.

Fix this by read-locking local->services_lock to access the AF_RXRPC socket
providing the service rather than RCU in rxrpc_new_incoming_call().
There's no real need to use RCU here as local->services_lock is only
write-locked by the socket side in two places: when binding and when
shutting down.

Fixes: 5e6ef4f1017c ("rxrpc: Make the I/O thread take over the call and local processor work")
Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
net/rxrpc/af_rxrpc.c
net/rxrpc/ar-internal.h
net/rxrpc/call_accept.c
net/rxrpc/security.c