From: David Howells dhowells@redhat.com
commit 7b5eab57cac45e270a0ad624ba157c5b30b3d44d upstream.
At the end of rxrpc_release_call(), rxrpc_cleanup_ring() is called to clear the Rx/Tx skbuff ring, but this doesn't lock the ring whilst it's accessing it. Unfortunately, rxrpc_resend() might be trying to retransmit a packet concurrently with this - and whilst it does lock the ring, this isn't protection against rxrpc_cleanup_call().
Fix this by removing the call to rxrpc_cleanup_ring() from rxrpc_release_call(). rxrpc_cleanup_ring() will be called again anyway from rxrpc_cleanup_call(). The earlier call is just an optimisation to recycle skbuffs more quickly.
Alternative solutions include rxrpc_release_call() could try to cancel the work item or wait for it to complete or rxrpc_cleanup_ring() could lock when accessing the ring (which would require a bh lock).
This can produce a report like the following:
BUG: KASAN: use-after-free in rxrpc_send_data_packet+0x19b4/0x1e70 net/rxrpc/output.c:372 Read of size 4 at addr ffff888011606e04 by task kworker/0:0/5 ... Workqueue: krxrpcd rxrpc_process_call Call Trace: ... kasan_report.cold+0x79/0xd5 mm/kasan/report.c:413 rxrpc_send_data_packet+0x19b4/0x1e70 net/rxrpc/output.c:372 rxrpc_resend net/rxrpc/call_event.c:266 [inline] rxrpc_process_call+0x1634/0x1f60 net/rxrpc/call_event.c:412 process_one_work+0x98d/0x15f0 kernel/workqueue.c:2275 ...
Allocated by task 2318: ... sock_alloc_send_pskb+0x793/0x920 net/core/sock.c:2348 rxrpc_send_data+0xb51/0x2bf0 net/rxrpc/sendmsg.c:358 rxrpc_do_sendmsg+0xc03/0x1350 net/rxrpc/sendmsg.c:744 rxrpc_sendmsg+0x420/0x630 net/rxrpc/af_rxrpc.c:560 ...
Freed by task 2318: ... kfree_skb+0x140/0x3f0 net/core/skbuff.c:704 rxrpc_free_skb+0x11d/0x150 net/rxrpc/skbuff.c:78 rxrpc_cleanup_ring net/rxrpc/call_object.c:485 [inline] rxrpc_release_call+0x5dd/0x860 net/rxrpc/call_object.c:552 rxrpc_release_calls_on_socket+0x21c/0x300 net/rxrpc/call_object.c:579 rxrpc_release_sock net/rxrpc/af_rxrpc.c:885 [inline] rxrpc_release+0x263/0x5a0 net/rxrpc/af_rxrpc.c:916 __sock_release+0xcd/0x280 net/socket.c:597 ...
The buggy address belongs to the object at ffff888011606dc0 which belongs to the cache skbuff_head_cache of size 232
Fixes: 248f219cb8bc ("rxrpc: Rewrite the data and ack handling code") Reported-by: syzbot+174de899852504e4a74a@syzkaller.appspotmail.com Reported-by: syzbot+3d1c772efafd3c38d007@syzkaller.appspotmail.com Signed-off-by: David Howells dhowells@redhat.com cc: Hillf Danton hdanton@sina.com Link: https://lore.kernel.org/r/161234207610.653119.5287360098400436976.stgit@wart... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/rxrpc/call_object.c | 2 -- 1 file changed, 2 deletions(-)
--- a/net/rxrpc/call_object.c +++ b/net/rxrpc/call_object.c @@ -548,8 +548,6 @@ void rxrpc_release_call(struct rxrpc_soc rxrpc_disconnect_call(call); if (call->security) call->security->free_call_crypto(call); - - rxrpc_cleanup_ring(call); _leave(""); }