2017-12-28 08:49:01

by Dmitry Vyukov

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

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: [email protected]
Signed-off-by: Dmitry Vyukov <[email protected]>
Cc: Pablo Neira Ayuso <[email protected]>
Cc: Jozsef Kadlecsik <[email protected]>
Cc: Florian Westphal <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
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 <[email protected]>");
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

2018-01-06 14:07:30

by Dmitry Vyukov

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

On Thu, Dec 28, 2017 at 9:48 AM, Dmitry Vyukov <[email protected]> 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: [email protected]
> Signed-off-by: Dmitry Vyukov <[email protected]>
> Cc: Pablo Neira Ayuso <[email protected]>
> Cc: Jozsef Kadlecsik <[email protected]>
> Cc: Florian Westphal <[email protected]>
> Cc: "David S. Miller" <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> ---
> 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 <[email protected]>");
> 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?

2018-01-06 22:52:22

by Pablo Neira Ayuso

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

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.