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Subject[PATCH] ipv4: fix a RCU-list lock in fib_triestat_seq_show
Date
fib_triestat_seq_show() calls hlist_for_each_entry_rcu(tb, head,
tb_hlist) without rcu_read_lock() will trigger a warning,

net/ipv4/fib_trie.c:2579 RCU-list traversed in non-reader section!!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
1 lock held by proc01/115277:
#0: c0000014507acf00 (&p->lock){+.+.}-{3:3}, at: seq_read+0x58/0x670

Call Trace:
dump_stack+0xf4/0x164 (unreliable)
lockdep_rcu_suspicious+0x140/0x164
fib_triestat_seq_show+0x750/0x880
seq_read+0x1a0/0x670
proc_reg_read+0x10c/0x1b0
__vfs_read+0x3c/0x70
vfs_read+0xac/0x170
ksys_read+0x7c/0x140
system_call+0x5c/0x68

Signed-off-by: Qian Cai <cai@lca.pw>
---
net/ipv4/fib_trie.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index ff0c24371e33..73fa37476f03 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -2577,6 +2577,7 @@ static int fib_triestat_seq_show(struct seq_file *seq, void *v)
" %zd bytes, size of tnode: %zd bytes.\n",
LEAF_SIZE, TNODE_SIZE(0));

+ rcu_read_lock();
for (h = 0; h < FIB_TABLE_HASHSZ; h++) {
struct hlist_head *head = &net->ipv4.fib_table_hash[h];
struct fib_table *tb;
@@ -2597,6 +2598,7 @@ static int fib_triestat_seq_show(struct seq_file *seq, void *v)
#endif
}
}
+ rcu_read_unlock();

return 0;
}
--
2.21.0 (Apple Git-122.2)
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