On Wed, Jul 31, 2013 at 6:43 PM, Hannes Frederic Sowa <han...@stressinduktion.org> wrote: > On Wed, Jul 31, 2013 at 05:55:13AM -0700, Paul E. McKenney wrote: >> On Wed, Jul 31, 2013 at 04:40:47PM +0530, vinayak menon wrote: >> > Hi, >> > >> > A crash was seen on 3.4.5 kernel during some random wlan operations. >> > >> > CPU: Single core ARM Cortex A9. >> > >> > fib_route_seq_next was called with second argument (void *v) as 0xd6e3e360 >> > which is a "freed" object of the "ip_fib_trie" cache. I confirmed that the >> > object was freed with crash utility. >> > >> > Sequence: fib_route_seq_next->trie_nextleaf->leaf_walk_rcu >> > >> > As "v" was a freed object, inside trie_nextleaf(), node_parent_rcu() >> > returned an invalid tnode. But as I had enabled slab poisoning and the >> > object was already freed, the tnode was 0x6b6b6b6b. And this was passed to >> > leaf_walk_rcu and resulted in the crash. >> > >> > fib_route_seq_start, takes rcu_read_lock(), but free_leaf >> > calls call_rcu_bh. Can this be the problem ? >> > Should rcu_read_lock() in fib_route_seq_start be changed to >> > rcu_read_lock_bh() >> > ? >> >> One way or the other, the RCU read-side primitives need to match the RCU >> update-side primitives. Adding netdev... > > Already fixed by: > > commit 0c03eca3d995e73d691edea8c787e25929ec156d > Author: Eric Dumazet <eduma...@google.com> > Date: Tue Aug 7 00:47:11 2012 +0000 > > net: fib: fix incorrect call_rcu_bh() > > After IP route cache removal, I believe rcu_bh() has very little use and > we should remove this RCU variant, since it adds some cycles in fast > path. > > Anyway, the call_rcu_bh() use in fib_true is obviously wrong, since > some users only assert rcu_read_lock(). >
Thanks. I missed this somehow. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
