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author | Liping Zhang | 2016-07-03 07:18:43 +0200 |
---|---|---|
committer | Pablo Neira Ayuso | 2016-07-11 11:38:57 +0200 |
commit | 64b87639c9cbeb03e26bc65528416c961b1dde96 (patch) | |
tree | 2afc50f1b43b66f37f5fd07c3deefff94c960302 /net | |
parent | Merge tag 'mac80211-next-for-davem-2016-07-06' of git://git.kernel.org/pub/sc... (diff) | |
download | kernel-qcow2-linux-64b87639c9cbeb03e26bc65528416c961b1dde96.tar.gz kernel-qcow2-linux-64b87639c9cbeb03e26bc65528416c961b1dde96.tar.xz kernel-qcow2-linux-64b87639c9cbeb03e26bc65528416c961b1dde96.zip |
netfilter: conntrack: fix race between nf_conntrack proc read and hash resize
When we do "cat /proc/net/nf_conntrack", and meanwhile resize the conntrack
hash table via /sys/module/nf_conntrack/parameters/hashsize, race will
happen, because reader can observe a newly allocated hash but the old size
(or vice versa). So oops will happen like follows:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000017
IP: [<ffffffffa0418e21>] seq_print_acct+0x11/0x50 [nf_conntrack]
Call Trace:
[<ffffffffa0412f4e>] ? ct_seq_show+0x14e/0x340 [nf_conntrack]
[<ffffffff81261a1c>] seq_read+0x2cc/0x390
[<ffffffff812a8d62>] proc_reg_read+0x42/0x70
[<ffffffff8123bee7>] __vfs_read+0x37/0x130
[<ffffffff81347980>] ? security_file_permission+0xa0/0xc0
[<ffffffff8123cf75>] vfs_read+0x95/0x140
[<ffffffff8123e475>] SyS_read+0x55/0xc0
[<ffffffff817c2572>] entry_SYSCALL_64_fastpath+0x1a/0xa4
It is very easy to reproduce this kernel crash.
1. open one shell and input the following cmds:
while : ; do
echo $RANDOM > /sys/module/nf_conntrack/parameters/hashsize
done
2. open more shells and input the following cmds:
while : ; do
cat /proc/net/nf_conntrack
done
3. just wait a monent, oops will happen soon.
The solution in this patch is based on Florian's Commit 5e3c61f98175
("netfilter: conntrack: fix lookup race during hash resize"). And
add a wrapper function nf_conntrack_get_ht to get hash and hsize
suggested by Florian Westphal.
Signed-off-by: Liping Zhang <liping.zhang@spreadtrum.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'net')
-rw-r--r-- | net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c | 14 | ||||
-rw-r--r-- | net/netfilter/nf_conntrack_core.c | 17 | ||||
-rw-r--r-- | net/netfilter/nf_conntrack_standalone.c | 14 |
3 files changed, 36 insertions, 9 deletions
diff --git a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c index c6f3c406f707..63923710f325 100644 --- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c +++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c @@ -26,6 +26,8 @@ struct ct_iter_state { struct seq_net_private p; + struct hlist_nulls_head *hash; + unsigned int htable_size; unsigned int bucket; }; @@ -35,10 +37,10 @@ static struct hlist_nulls_node *ct_get_first(struct seq_file *seq) struct hlist_nulls_node *n; for (st->bucket = 0; - st->bucket < nf_conntrack_htable_size; + st->bucket < st->htable_size; st->bucket++) { n = rcu_dereference( - hlist_nulls_first_rcu(&nf_conntrack_hash[st->bucket])); + hlist_nulls_first_rcu(&st->hash[st->bucket])); if (!is_a_nulls(n)) return n; } @@ -53,11 +55,11 @@ static struct hlist_nulls_node *ct_get_next(struct seq_file *seq, head = rcu_dereference(hlist_nulls_next_rcu(head)); while (is_a_nulls(head)) { if (likely(get_nulls_value(head) == st->bucket)) { - if (++st->bucket >= nf_conntrack_htable_size) + if (++st->bucket >= st->htable_size) return NULL; } head = rcu_dereference( - hlist_nulls_first_rcu(&nf_conntrack_hash[st->bucket])); + hlist_nulls_first_rcu(&st->hash[st->bucket])); } return head; } @@ -75,7 +77,11 @@ static struct hlist_nulls_node *ct_get_idx(struct seq_file *seq, loff_t pos) static void *ct_seq_start(struct seq_file *seq, loff_t *pos) __acquires(RCU) { + struct ct_iter_state *st = seq->private; + rcu_read_lock(); + + nf_conntrack_get_ht(&st->hash, &st->htable_size); return ct_get_idx(seq, *pos); } diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index 153e33ffeeaa..1289e7e5e0de 100644 --- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c @@ -460,6 +460,23 @@ nf_ct_key_equal(struct nf_conntrack_tuple_hash *h, net_eq(net, nf_ct_net(ct)); } +/* must be called with rcu read lock held */ +void nf_conntrack_get_ht(struct hlist_nulls_head **hash, unsigned int *hsize) +{ + struct hlist_nulls_head *hptr; + unsigned int sequence, hsz; + + do { + sequence = read_seqcount_begin(&nf_conntrack_generation); + hsz = nf_conntrack_htable_size; + hptr = nf_conntrack_hash; + } while (read_seqcount_retry(&nf_conntrack_generation, sequence)); + + *hash = hptr; + *hsize = hsz; +} +EXPORT_SYMBOL_GPL(nf_conntrack_get_ht); + /* * Warning : * - Caller must take a reference on returned object diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c index 2aaa188ee961..958a1455ca7f 100644 --- a/net/netfilter/nf_conntrack_standalone.c +++ b/net/netfilter/nf_conntrack_standalone.c @@ -48,6 +48,8 @@ EXPORT_SYMBOL_GPL(print_tuple); struct ct_iter_state { struct seq_net_private p; + struct hlist_nulls_head *hash; + unsigned int htable_size; unsigned int bucket; u_int64_t time_now; }; @@ -58,9 +60,10 @@ static struct hlist_nulls_node *ct_get_first(struct seq_file *seq) struct hlist_nulls_node *n; for (st->bucket = 0; - st->bucket < nf_conntrack_htable_size; + st->bucket < st->htable_size; st->bucket++) { - n = rcu_dereference(hlist_nulls_first_rcu(&nf_conntrack_hash[st->bucket])); + n = rcu_dereference( + hlist_nulls_first_rcu(&st->hash[st->bucket])); if (!is_a_nulls(n)) return n; } @@ -75,12 +78,11 @@ static struct hlist_nulls_node *ct_get_next(struct seq_file *seq, head = rcu_dereference(hlist_nulls_next_rcu(head)); while (is_a_nulls(head)) { if (likely(get_nulls_value(head) == st->bucket)) { - if (++st->bucket >= nf_conntrack_htable_size) + if (++st->bucket >= st->htable_size) return NULL; } head = rcu_dereference( - hlist_nulls_first_rcu( - &nf_conntrack_hash[st->bucket])); + hlist_nulls_first_rcu(&st->hash[st->bucket])); } return head; } @@ -102,6 +104,8 @@ static void *ct_seq_start(struct seq_file *seq, loff_t *pos) st->time_now = ktime_get_real_ns(); rcu_read_lock(); + + nf_conntrack_get_ht(&st->hash, &st->htable_size); return ct_get_idx(seq, *pos); } |