Messages in this thread Patch in this message | | | Subject | [PATCH] fib: add rtnl locking in ip_fib_net_exit | From | Eric Dumazet <> | Date | Wed, 30 Mar 2011 14:28:02 +0200 |
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Le mercredi 30 mars 2011 à 18:05 +0800, Daniel J Blueman a écrit : > The loop in fib_table_flush [1] calls trie_firstleaf() which > RCU-dereferences a structure outside a RCU read critical section, > generating a warning [2]. >
Hi Daniel
> Since trie_leaf_remove() uses rcu_assign_pointer(), which should be > outside the RCU read critical section, is there any better solution > than spitting up the loop, with the first half covered by a RCU read > critical section lock? >
rcu_assign_pointer() can be done anywhere. This is done by a writer (holding RTNL), while RCU read is used by readers.
> Daniel > > --- [1] > > int fib_table_flush(struct fib_table *tb) > { > struct trie *t = (struct trie *) tb->tb_data; > struct leaf *l, *ll = NULL; > int found = 0; > > for (l = trie_firstleaf(t); l; l = trie_nextleaf(l)) { > found += trie_flush_leaf(l); > > if (ll && hlist_empty(&ll->list)) > trie_leaf_remove(t, ll); > ll = l; > } > > --- [2] > > =================================================== > [ INFO: suspicious rcu_dereference_check() usage. ] > --------------------------------------------------- > net/ipv4/fib_trie.c:1777 invoked rcu_dereference_check() without protection! > > other info that might help us debug this: > > rcu_scheduler_active = 1, debug_locks = 1 > 3 locks held by kworker/u:5/51: > #0: (netns){.+.+.+}, at: [<ffffffff8107b639>] process_one_work+0x149/0x470 > #1: (net_cleanup_work){+.+.+.}, at: [<ffffffff8107b639>] > process_one_work+0x149/0x470 > #2: (net_mutex){+.+.+.}, at: [<ffffffff8157b4b0>] cleanup_net+0x80/0x1b0 > > stack backtrace: > Pid: 51, comm: kworker/u:5 Tainted: G W 2.6.39-rc1-350cd #1 > Call Trace: > [<ffffffff81094cd4>] lockdep_rcu_dereference+0xa4/0xc0 > [<ffffffff8160aa23>] trie_firstleaf+0x93/0xa0 > [<ffffffff8156feb8>] ? __sk_free+0x148/0x1e0 > [<ffffffff8160d890>] fib_table_flush+0x20/0x1a0 > [<ffffffff81606da5>] ip_fib_net_exit+0x95/0xd0 > [<ffffffff81606e10>] fib_net_exit+0x30/0x40 > [<ffffffff8157ab8e>] ops_exit_list+0x2e/0x70 > [<ffffffff8157b52b>] cleanup_net+0xfb/0x1b0 > [<ffffffff8107b69a>] process_one_work+0x1aa/0x470 > [<ffffffff8107b639>] ? process_one_work+0x149/0x470 > [<ffffffff8157b430>] ? net_free+0x30/0x30 > [<ffffffff8107bd97>] worker_thread+0x157/0x3c0 > [<ffffffff816ea484>] ? preempt_schedule+0x44/0x60 > [<ffffffff8107bc40>] ? rescuer_thread+0x2e0/0x2e0 > [<ffffffff81080236>] kthread+0xb6/0xc0 > [<ffffffff81095f1d>] ? trace_hardirqs_on_caller+0x14d/0x190 > [<ffffffff816ef094>] kernel_thread_helper+0x4/0x10 > [<ffffffff810553f8>] ? finish_task_switch+0x78/0x110 > [<ffffffff816ed7c4>] ? retint_restore_args+0xe/0xe > [<ffffffff81080180>] ? __init_kthread_worker+0x70/0x70 > [<ffffffff816ef090>] ? gs_change+0xb/0xb
So fib_table_flush() is called (from ip_fib_net_exit) without RTNL being held.
Here is patch to fix this.
Thanks
[PATCH] fib: add rtnl locking in ip_fib_net_exit
Daniel J Blueman reported a lockdep splat in trie_firstleaf(), caused by RTNL being not locked before a call to fib_table_flush()
Reported-by: Daniel J Blueman <daniel.blueman@gmail.com> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> --- net/ipv4/fib_frontend.c | 2 ++ 1 files changed, 2 insertions(+)
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c index f116ce8..4510883 100644 --- a/net/ipv4/fib_frontend.c +++ b/net/ipv4/fib_frontend.c @@ -1068,6 +1068,7 @@ static void ip_fib_net_exit(struct net *net) fib4_rules_exit(net); #endif + rtnl_lock(); for (i = 0; i < FIB_TABLE_HASHSZ; i++) { struct fib_table *tb; struct hlist_head *head; @@ -1080,6 +1081,7 @@ static void ip_fib_net_exit(struct net *net) fib_free_table(tb); } } + rtnl_unlock(); kfree(net->ipv4.fib_table_hash); }
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