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Date: Tue, 9 Aug 2011 18:02:40 +0100 From: Mark Rutland <mark.rutland@....com> To: netdev@...r.kernel.org Cc: Mark Rutland <mark.rutland@....com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <eric.dumazet@...il.com>, Gergely Kalman <synapse@...py.csoma.elte.hu> Subject: [PATCH] Fix RCU warning in rt_cache_seq_show Commit f2c31e32 ("net: fix NULL dereferences in check_peer_redir()") added rcu protection to dst neighbour, and updated callsites for dst_{get,set}_neighbour. Unfortunately, it missed rt_cache_seq_show. This produces a warning on v3.1-rc1 (on a preemptible kernel, on an ARM Vexpress A9x4): =================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- include/net/dst.h:91 invoked rcu_dereference_check() without protection! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 0 2 locks held by proc01/32159: stack backtrace: [<80014880>] (unwind_backtrace+0x0/0xf8) from [<802e5c78>] (rt_cache_seq_show+0x18c/0x1c4) [<802e5c78>] (rt_cache_seq_show+0x18c/0x1c4) from [<800e0c5c>] (seq_read+0x324/0x4a4) [<800e0c5c>] (seq_read+0x324/0x4a4) from [<8010786c>] (proc_reg_read+0x70/0x94) [<8010786c>] (proc_reg_read+0x70/0x94) from [<800c0ba8>] (vfs_read+0xb0/0x144) [<800c0ba8>] (vfs_read+0xb0/0x144) from [<800c0ea8>] (sys_read+0x40/0x70) [<800c0ea8>] (sys_read+0x40/0x70) from [<8000e0c0>] (ret_fast_syscall+0x0/0x3c) This patch adds calls to rcu_read_{lock,unlock} in rt_cache_seq_show, protecting the dereferenced variable, and clearing the warning. Signed-off-by: Mark Rutland <mark.rutland@....com> Cc: David S. Miller <davem@...emloft.net> Cc: Eric Dumazet <eric.dumazet@...il.com> Cc: Gergely Kalman <synapse@...py.csoma.elte.hu> --- net/ipv4/route.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/net/ipv4/route.c b/net/ipv4/route.c index e3dec1c..6699ef7 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -419,6 +419,7 @@ static int rt_cache_seq_show(struct seq_file *seq, void *v) struct neighbour *n; int len; + rcu_read_lock(); n = dst_get_neighbour(&r->dst); 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", @@ -435,6 +436,7 @@ static int rt_cache_seq_show(struct seq_file *seq, void *v) -1, (n && (n->nud_state & NUD_CONNECTED)) ? 1 : 0, r->rt_spec_dst, &len); + rcu_read_unlock(); seq_printf(seq, "%*s\n", 127 - len, ""); } -- 1.7.0.4 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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