diff mbox series

[net,1/5] netfilter: nft_ct: protect nft_ct_pcpu_template_refcnt with mutex

Message ID 20210903163020.13741-2-pablo@netfilter.org
State Accepted
Delegated to: Pablo Neira
Headers show
Series [net,1/5] netfilter: nft_ct: protect nft_ct_pcpu_template_refcnt with mutex | expand

Commit Message

Pablo Neira Ayuso Sept. 3, 2021, 4:30 p.m. UTC 
From: Pavel Skripkin <paskripkin@gmail.com>

Syzbot hit use-after-free in nf_tables_dump_sets. The problem was in
missing lock protection for nft_ct_pcpu_template_refcnt.

Before commit f102d66b335a ("netfilter: nf_tables: use dedicated
mutex to guard transactions") all transactions were serialized by global
mutex, but then global mutex was changed to local per netnamespace
commit_mutex.

This change causes use-after-free bug, when 2 netnamespaces concurently
changing nft_ct_pcpu_template_refcnt without proper locking. Fix it by
adding nft_ct_pcpu_mutex and protect all nft_ct_pcpu_template_refcnt
changes with it.

Fixes: f102d66b335a ("netfilter: nf_tables: use dedicated mutex to guard transactions")
Reported-and-tested-by: syzbot+649e339fa6658ee623d3@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nft_ct.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

Comments

patchwork-bot+netdevbpf@kernel.org Sept. 4, 2021, 1:30 a.m. UTC | #1 
Hello:

This series was applied to netdev/net.git (refs/heads/master):

On Fri,  3 Sep 2021 18:30:16 +0200 you wrote:
> From: Pavel Skripkin <paskripkin@gmail.com>
> 
> Syzbot hit use-after-free in nf_tables_dump_sets. The problem was in
> missing lock protection for nft_ct_pcpu_template_refcnt.
> 
> Before commit f102d66b335a ("netfilter: nf_tables: use dedicated
> mutex to guard transactions") all transactions were serialized by global
> mutex, but then global mutex was changed to local per netnamespace
> commit_mutex.
> 
> [...]

Here is the summary with links:
  - [net,1/5] netfilter: nft_ct: protect nft_ct_pcpu_template_refcnt with mutex
    https://git.kernel.org/netdev/net/c/e3245a7b7b34
  - [net,2/5] netfilter: conntrack: sanitize table size default settings
    https://git.kernel.org/netdev/net/c/d532bcd0b269
  - [net,3/5] netfilter: conntrack: switch to siphash
    https://git.kernel.org/netdev/net/c/dd6d2910c5e0
  - [net,4/5] netfilter: refuse insertion if chain has grown too large
    https://git.kernel.org/netdev/net/c/d7e7747ac5c2
  - [net,5/5] netfilter: socket: icmp6: fix use-after-scope
    https://git.kernel.org/netdev/net/c/730affed24bf

You are awesome, thank you!
--
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diff mbox series

Patch

diff --git a/net/netfilter/nft_ct.c b/net/netfilter/nft_ct.c
index 337e22d8b40b..99b1de14ff7e 100644
--- a/net/netfilter/nft_ct.c
+++ b/net/netfilter/nft_ct.c
@@ -41,6 +41,7 @@  struct nft_ct_helper_obj  {
 #ifdef CONFIG_NF_CONNTRACK_ZONES
 static DEFINE_PER_CPU(struct nf_conn *, nft_ct_pcpu_template);
 static unsigned int nft_ct_pcpu_template_refcnt __read_mostly;
+static DEFINE_MUTEX(nft_ct_pcpu_mutex);
 #endif
 
 static u64 nft_ct_get_eval_counter(const struct nf_conn_counter *c,
@@ -525,8 +526,10 @@  static void __nft_ct_set_destroy(const struct nft_ctx *ctx, struct nft_ct *priv)
 #endif
 #ifdef CONFIG_NF_CONNTRACK_ZONES
 	case NFT_CT_ZONE:
+		mutex_lock(&nft_ct_pcpu_mutex);
 		if (--nft_ct_pcpu_template_refcnt == 0)
 			nft_ct_tmpl_put_pcpu();
+		mutex_unlock(&nft_ct_pcpu_mutex);
 		break;
 #endif
 	default:
@@ -564,9 +567,13 @@  static int nft_ct_set_init(const struct nft_ctx *ctx,
 #endif
 #ifdef CONFIG_NF_CONNTRACK_ZONES
 	case NFT_CT_ZONE:
-		if (!nft_ct_tmpl_alloc_pcpu())
+		mutex_lock(&nft_ct_pcpu_mutex);
+		if (!nft_ct_tmpl_alloc_pcpu()) {
+			mutex_unlock(&nft_ct_pcpu_mutex);
 			return -ENOMEM;
+		}
 		nft_ct_pcpu_template_refcnt++;
+		mutex_unlock(&nft_ct_pcpu_mutex);
 		len = sizeof(u16);
 		break;
 #endif