Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 5.5 01/46] ipv4: fix a RCU-list lock in fib_triestat_seq_show | Date | Tue, 7 Apr 2020 12:21:32 +0200 |
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From: Qian Cai <cai@lca.pw>
[ Upstream commit fbe4e0c1b298b4665ee6915266c9d6c5b934ef4a ]
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- net/ipv4/fib_trie.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -2473,6 +2473,7 @@ static int fib_triestat_seq_show(struct " %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; @@ -2492,7 +2493,9 @@ static int fib_triestat_seq_show(struct trie_show_usage(seq, t->stats); #endif } + cond_resched_rcu(); } + rcu_read_unlock(); return 0; }
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