| Message ID | 155660964874.18872.7446174793302616529.stgit@warthog.procyon.org.uk |
|---|---|
| State | Accepted |
| Delegated to: | David Miller |
| Headers | show |
| Series | [net] rxrpc: Fix net namespace cleanup | expand |
From: David Howells <dhowells@redhat.com> Date: Tue, 30 Apr 2019 08:34:08 +0100 > In rxrpc_destroy_all_calls(), there are two phases: (1) make sure the > ->calls list is empty, emitting error messages if not, and (2) wait for the > RCU cleanup to happen on outstanding calls (ie. ->nr_calls becomes 0). > > To avoid taking the call_lock, the function prechecks ->calls and if empty, > it returns to avoid taking the lock - this is wrong, however: it still > needs to go and do the second phase and wait for ->nr_calls to become 0. > > Without this, the rxrpc_net struct may get deallocated before we get to the > RCU cleanup for the last calls. This can lead to: > > Slab corruption (Not tainted): kmalloc-16k start=ffff88802b178000, len=16384 > 050: 6b 6b 6b 6b 6b 6b 6b 6b 61 6b 6b 6b 6b 6b 6b 6b kkkkkkkkakkkkkkk > > Note the "61" at offset 0x58. This corresponds to the ->nr_calls member of > struct rxrpc_net (which is >9k in size, and thus allocated out of the 16k > slab). > > > Fix this by flipping the condition on the if-statement, putting the locked > section inside the if-body and dropping the return from there. The > function will then always go on to wait for the RCU cleanup on outstanding > calls. > > Fixes: 2baec2c3f854 ("rxrpc: Support network namespacing") > Signed-off-by: David Howells <dhowells@redhat.com> Applied and queued up for -stable, thanks.
diff --git a/net/rxrpc/call_object.c b/net/rxrpc/call_object.c index 8aa2937b069f..fe96881a334d 100644 --- a/net/rxrpc/call_object.c +++ b/net/rxrpc/call_object.c @@ -604,30 +604,30 @@ void rxrpc_destroy_all_calls(struct rxrpc_net *rxnet) _enter(""); - if (list_empty(&rxnet->calls)) - return; + if (!list_empty(&rxnet->calls)) { + write_lock(&rxnet->call_lock); - write_lock(&rxnet->call_lock); + while (!list_empty(&rxnet->calls)) { + call = list_entry(rxnet->calls.next, + struct rxrpc_call, link); + _debug("Zapping call %p", call); - while (!list_empty(&rxnet->calls)) { - call = list_entry(rxnet->calls.next, struct rxrpc_call, link); - _debug("Zapping call %p", call); + rxrpc_see_call(call); + list_del_init(&call->link); - rxrpc_see_call(call); - list_del_init(&call->link); + pr_err("Call %p still in use (%d,%s,%lx,%lx)!\n", + call, atomic_read(&call->usage), + rxrpc_call_states[call->state], + call->flags, call->events); - pr_err("Call %p still in use (%d,%s,%lx,%lx)!\n", - call, atomic_read(&call->usage), - rxrpc_call_states[call->state], - call->flags, call->events); + write_unlock(&rxnet->call_lock); + cond_resched(); + write_lock(&rxnet->call_lock); + } write_unlock(&rxnet->call_lock); - cond_resched(); - write_lock(&rxnet->call_lock); } - write_unlock(&rxnet->call_lock); - atomic_dec(&rxnet->nr_calls); wait_var_event(&rxnet->nr_calls, !atomic_read(&rxnet->nr_calls)); }
In rxrpc_destroy_all_calls(), there are two phases: (1) make sure the ->calls list is empty, emitting error messages if not, and (2) wait for the RCU cleanup to happen on outstanding calls (ie. ->nr_calls becomes 0). To avoid taking the call_lock, the function prechecks ->calls and if empty, it returns to avoid taking the lock - this is wrong, however: it still needs to go and do the second phase and wait for ->nr_calls to become 0. Without this, the rxrpc_net struct may get deallocated before we get to the RCU cleanup for the last calls. This can lead to: Slab corruption (Not tainted): kmalloc-16k start=ffff88802b178000, len=16384 050: 6b 6b 6b 6b 6b 6b 6b 6b 61 6b 6b 6b 6b 6b 6b 6b kkkkkkkkakkkkkkk Note the "61" at offset 0x58. This corresponds to the ->nr_calls member of struct rxrpc_net (which is >9k in size, and thus allocated out of the 16k slab). Fix this by flipping the condition on the if-statement, putting the locked section inside the if-body and dropping the return from there. The function will then always go on to wait for the RCU cleanup on outstanding calls. Fixes: 2baec2c3f854 ("rxrpc: Support network namespacing") Signed-off-by: David Howells <dhowells@redhat.com> --- net/rxrpc/call_object.c | 32 ++++++++++++++++---------------- 1 file changed, 16 insertions(+), 16 deletions(-)