Messages in this thread | | | Date | Tue, 30 Apr 2019 10:53:06 -0400 (EDT) | Subject | Re: [PATCH net] rxrpc: Fix net namespace cleanup | From | David Miller <> |
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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.
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