Messages in this thread Patch in this message | | | Subject | Re: 3.2.0-rc3+ (Linus git - 883381d9f1c5a6329bbb796e23ae52c939940310) - INFO: suspicious RCU usage | From | Eric Dumazet <> | Date | Wed, 30 Nov 2011 07:05:55 +0100 |
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Le mercredi 30 novembre 2011 à 06:56 +0100, Eric Dumazet a écrit : > Le mercredi 30 novembre 2011 à 00:09 -0500, Miles Lane a écrit : > > I got the following message while running "find /proc | xargs head" to > > see whether accessing any proc files would cause trouble. > > > > [ 442.112632] [ INFO: suspicious RCU usage. ] > > [ 442.112634] ------------------------------- > > [ 442.112637] include/net/dst.h:91 suspicious rcu_dereference_check() usage! > > [ 442.112640] > > [ 442.112641] other info that might help us debug this: > > [ 442.112643] > > [ 442.112645] > > [ 442.112646] rcu_scheduler_active = 1, debug_locks = 1 > > [ 442.112650] 2 locks held by head/4903: > > [ 442.112652] #0: (&p->lock){+.+.+.}, at: [<ffffffff810e160a>] > > seq_read+0x38/0x35d > > [ 442.112665] #1: (rcu_read_lock_bh){.+....}, at: > > [<ffffffff812f831e>] rcu_read_lock_bh+0x0/0x35 > > [ 442.112676] > > [ 442.112677] stack backtrace: > > [ 442.112681] Pid: 4903, comm: head Not tainted 3.2.0-rc3+ #42 > > [ 442.112684] Call Trace: > > [ 442.112691] [<ffffffff8105cdd2>] lockdep_rcu_suspicious+0xaf/0xb8 > > [ 442.112697] [<ffffffff812f8e02>] dst_get_neighbour.isra.31+0x44/0x4c > > [ 442.112702] [<ffffffff812f8e86>] rt_cache_seq_show+0x46/0x194 > > [ 442.112708] [<ffffffff812f8351>] ? rcu_read_lock_bh+0x33/0x35 > > [ 442.112714] [<ffffffff8104b57a>] ? rcu_read_lock_bh_held+0x9/0x37 > > [ 442.112719] [<ffffffff812f85c2>] ? rt_cache_get_first+0x72/0x116 > > [ 442.112725] [<ffffffff810e184d>] seq_read+0x27b/0x35d > > [ 442.112730] [<ffffffff810e15d2>] ? seq_lseek+0xda/0xda > > [ 442.112736] [<ffffffff8110e3e1>] proc_reg_read+0x8e/0xad > > [ 442.112741] [<ffffffff810c6e23>] vfs_read+0xa0/0xc7 > > [ 442.112746] [<ffffffff810c80bf>] ? fget_light+0x35/0x98 > > [ 442.112750] [<ffffffff810c6e8f>] sys_read+0x45/0x69 > > [ 442.112756] [<ffffffff8136a27b>] system_call_fastpath+0x16/0x1b > > > Thanks for the report Miles, I'll provide a patch in a couple of minutes > after testing it > >
[PATCH] ipv4: fix lockdep splat in rt_cache_seq_show
After commit f2c31e32b378 (fix NULL dereferences in check_peer_redir()), dst_get_neighbour() should be guarded by rcu_read_lock() / rcu_read_unlock() section.
Reported-by: Miles Lane <miles.lane@gmail.com> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> --- net/ipv4/route.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 5c28472..57e01bc 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -417,9 +417,13 @@ static int rt_cache_seq_show(struct seq_file *seq, void *v) else { struct rtable *r = v; struct neighbour *n; - int len; + int len, HHUptod; + rcu_read_lock(); n = dst_get_neighbour(&r->dst); + HHUptod = (n && (n->nud_state & NUD_CONNECTED)) ? 1 : 0; + rcu_read_unlock(); + seq_printf(seq, "%s\t%08X\t%08X\t%8X\t%d\t%u\t%d\t" "%08X\t%d\t%u\t%u\t%02X\t%d\t%1d\t%08X%n", r->dst.dev ? r->dst.dev->name : "*", @@ -433,7 +437,7 @@ static int rt_cache_seq_show(struct seq_file *seq, void *v) dst_metric(&r->dst, RTAX_RTTVAR)), r->rt_key_tos, -1, - (n && (n->nud_state & NUD_CONNECTED)) ? 1 : 0, + HHUptod, r->rt_spec_dst, &len); seq_printf(seq, "%*s\n", 127 - len, "");
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