From: Pablo Neira Ayuso <pablo@netfilter.org>
To: netfilter-devel@vger.kernel.org
Cc: davem@davemloft.net, netdev@vger.kernel.org
Subject: [PATCH 5/6] netfilter: nf_conntrack: Fix possible possible crash on module loading.
Date: Mon, 9 Jul 2018 19:19:03 +0200 [thread overview]
Message-ID: <20180709171904.2460-6-pablo@netfilter.org> (raw)
In-Reply-To: <20180709171904.2460-1-pablo@netfilter.org>
From: Andrey Ryabinin <aryabinin@virtuozzo.com>
Loading the nf_conntrack module with doubled hashsize parameter, i.e.
modprobe nf_conntrack hashsize=12345 hashsize=12345
causes NULL-ptr deref.
If 'hashsize' specified twice, the nf_conntrack_set_hashsize() function
will be called also twice.
The first nf_conntrack_set_hashsize() call will set the
'nf_conntrack_htable_size' variable:
nf_conntrack_set_hashsize()
...
/* On boot, we can set this without any fancy locking. */
if (!nf_conntrack_htable_size)
return param_set_uint(val, kp);
But on the second invocation, the nf_conntrack_htable_size is already set,
so the nf_conntrack_set_hashsize() will take a different path and call
the nf_conntrack_hash_resize() function. Which will crash on the attempt
to dereference 'nf_conntrack_hash' pointer:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
RIP: 0010:nf_conntrack_hash_resize+0x255/0x490 [nf_conntrack]
Call Trace:
nf_conntrack_set_hashsize+0xcd/0x100 [nf_conntrack]
parse_args+0x1f9/0x5a0
load_module+0x1281/0x1a50
__se_sys_finit_module+0xbe/0xf0
do_syscall_64+0x7c/0x390
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Fix this, by checking !nf_conntrack_hash instead of
!nf_conntrack_htable_size. nf_conntrack_hash will be initialized only
after the module loaded, so the second invocation of the
nf_conntrack_set_hashsize() won't crash, it will just reinitialize
nf_conntrack_htable_size again.
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
net/netfilter/nf_conntrack_core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 3465da2a98bd..3d5280425027 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -2043,7 +2043,7 @@ int nf_conntrack_set_hashsize(const char *val, const struct kernel_param *kp)
return -EOPNOTSUPP;
/* On boot, we can set this without any fancy locking. */
- if (!nf_conntrack_htable_size)
+ if (!nf_conntrack_hash)
return param_set_uint(val, kp);
rc = kstrtouint(val, 0, &hashsize);
--
2.11.0
next prev parent reply other threads:[~2018-07-09 17:19 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-09 17:18 [PATCH 0/6] Netfilter fixes for net Pablo Neira Ayuso
2018-07-09 17:18 ` [PATCH 1/6] netfilter: x_tables: set module owner for icmp(6) matches Pablo Neira Ayuso
2018-07-09 17:19 ` [PATCH 2/6] netfilter: nf_tproxy: fix possible non-linear access to transport header Pablo Neira Ayuso
2018-07-09 17:19 ` [PATCH 3/6] netfilter: nf_tables: place all set backends in one single module Pablo Neira Ayuso
2018-07-09 17:19 ` [PATCH 4/6] netfilter: nft_compat: explicitly reject ERROR and standard target Pablo Neira Ayuso
2018-07-09 17:19 ` Pablo Neira Ayuso [this message]
2018-07-09 17:19 ` [PATCH 6/6] netfilter: ipv6: nf_defrag: drop skb dst before queueing Pablo Neira Ayuso
2018-07-09 21:24 ` [PATCH 0/6] Netfilter fixes for net David Miller
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