[PATCH] netfilter: fix int overflow in xt_alloc_table_info()

[PATCH] netfilter: fix int overflow in xt_alloc_table_info()

[Dmitry Vyukov]

syzkaller triggered OOM kills by passing ipt_replace.size = -1
to IPT_SO_SET_REPLACE. The root cause is that SMP_ALIGN() in
xt_alloc_table_info() causes int overflow and the size check passes
when it should not. SMP_ALIGN() is no longer needed leftover.

Remove SMP_ALIGN() call in xt_alloc_table_info().

Reported-by: syzbot+4396883fa8c4f64e0175@syzkaller.appspotmail.com
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Cc: Florian Westphal <fw@strlen.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: netfilter-devel@vger.kernel.org
Cc: coreteam@netfilter.org
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 net/netfilter/x_tables.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 55802e97f906..e02a21549c99 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -39,7 +39,6 @@ MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
 MODULE_DESCRIPTION("{ip,ip6,arp,eb}_tables backend module");
 
-#define SMP_ALIGN(x) (((x) + SMP_CACHE_BYTES-1) & ~(SMP_CACHE_BYTES-1))
 #define XT_PCPU_BLOCK_SIZE 4096
 
 struct compat_delta {
@@ -1000,7 +999,7 @@ struct xt_table_info *xt_alloc_table_info(unsigned int size)
 		return NULL;
 
 	/* Pedantry: prevent them from hitting BUG() in vmalloc.c --RR */
-	if ((SMP_ALIGN(size) >> PAGE_SHIFT) + 2 > totalram_pages)
+	if ((size >> PAGE_SHIFT) + 2 > totalram_pages)
 		return NULL;
 
 	info = kvmalloc(sz, GFP_KERNEL);
-- 
2.15.1.620.gb9897f4670-goog

Re: [PATCH] netfilter: fix int overflow in xt_alloc_table_info()

[Dmitry Vyukov]

On Thu, Dec 28, 2017 at 9:48 AM, Dmitry Vyukov <dvyukov@google.com> wrote:
> syzkaller triggered OOM kills by passing ipt_replace.size = -1
> to IPT_SO_SET_REPLACE. The root cause is that SMP_ALIGN() in
> xt_alloc_table_info() causes int overflow and the size check passes
> when it should not. SMP_ALIGN() is no longer needed leftover.
>
> Remove SMP_ALIGN() call in xt_alloc_table_info().
>
> Reported-by: syzbot+4396883fa8c4f64e0175@syzkaller.appspotmail.com
> Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
> Cc: Pablo Neira Ayuso <pablo@netfilter.org>
> Cc: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
> Cc: Florian Westphal <fw@strlen.de>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: netfilter-devel@vger.kernel.org
> Cc: coreteam@netfilter.org
> Cc: netdev@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> ---
>  net/netfilter/x_tables.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
> index 55802e97f906..e02a21549c99 100644
> --- a/net/netfilter/x_tables.c
> +++ b/net/netfilter/x_tables.c
> @@ -39,7 +39,6 @@ MODULE_LICENSE("GPL");
>  MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
>  MODULE_DESCRIPTION("{ip,ip6,arp,eb}_tables backend module");
>
> -#define SMP_ALIGN(x) (((x) + SMP_CACHE_BYTES-1) & ~(SMP_CACHE_BYTES-1))
>  #define XT_PCPU_BLOCK_SIZE 4096
>
>  struct compat_delta {
> @@ -1000,7 +999,7 @@ struct xt_table_info *xt_alloc_table_info(unsigned int size)
>                 return NULL;
>
>         /* Pedantry: prevent them from hitting BUG() in vmalloc.c --RR */
> -       if ((SMP_ALIGN(size) >> PAGE_SHIFT) + 2 > totalram_pages)
> +       if ((size >> PAGE_SHIFT) + 2 > totalram_pages)
>                 return NULL;
>
>         info = kvmalloc(sz, GFP_KERNEL);


Ping.

Dave, will this go into net/net-next?

Re: [PATCH] netfilter: fix int overflow in xt_alloc_table_info()

[Pablo Neira Ayuso]

On Thu, Dec 28, 2017 at 09:48:54AM +0100, Dmitry Vyukov wrote:
> syzkaller triggered OOM kills by passing ipt_replace.size = -1
> to IPT_SO_SET_REPLACE. The root cause is that SMP_ALIGN() in
> xt_alloc_table_info() causes int overflow and the size check passes
> when it should not. SMP_ALIGN() is no longer needed leftover.
> 
> Remove SMP_ALIGN() call in xt_alloc_table_info().

Applied, thanks.