blob: e3bef67bf3d2c8d668bff3570112c736cc6de058 [file] [log] [blame]
From 31015932b2e0f92626da1a9d94e9e300061c6938 Mon Sep 17 00:00:00 2001
From: Qian Cai <cai@lca.pw>
Date: Wed, 25 Mar 2020 18:01:00 -0400
Subject: [PATCH] ipv4: fix a RCU-list lock in fib_triestat_seq_show
commit fbe4e0c1b298b4665ee6915266c9d6c5b934ef4a upstream.
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
Fix it by adding a pair of rcu_read_lock/unlock() and use
cond_resched_rcu() to avoid the situation where walking of a large
number of items may prevent scheduling for a long time.
Signed-off-by: Qian Cai <cai@lca.pw>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index e6261756057f..77da7df84494 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -2347,6 +2347,7 @@ 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;
@@ -2366,7 +2367,9 @@ static int fib_triestat_seq_show(struct seq_file *seq, void *v)
trie_show_usage(seq, t->stats);
#endif
}
+ cond_resched_rcu();
}
+ rcu_read_unlock();
return 0;
}
--
2.27.0