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* [PATCH v2 net] ipv6: fix out-of-bound access in ip6_parse_tlv()
@ 2021-06-24 10:07 Eric Dumazet
  2021-06-24 13:15 ` Paolo Abeni
  2021-06-24 19:50 ` patchwork-bot+netdevbpf
  0 siblings, 2 replies; 3+ messages in thread
From: Eric Dumazet @ 2021-06-24 10:07 UTC (permalink / raw)
  To: David S . Miller, Jakub Kicinski
  Cc: netdev, Eric Dumazet, Eric Dumazet, Paolo Abeni, Tom Herbert

From: Eric Dumazet <edumazet@google.com>

First problem is that optlen is fetched without checking
there is more than one byte to parse.

Fix this by taking care of IPV6_TLV_PAD1 before
fetching optlen (under appropriate sanity checks against len)

Second problem is that IPV6_TLV_PADN checks of zero
padding are performed before the check of remaining length.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Fixes: c1412fce7ecc ("net/ipv6/exthdrs.c: Strict PadN option checking")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Tom Herbert <tom@herbertland.com>
---
v2: Removed not needed optlen assignment for IPV6_TLV_PAD1 handling,
    added the Fixes: tag for first problem, feedback from Paolo, thanks !

 net/ipv6/exthdrs.c | 27 +++++++++++++--------------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
index 6f7da8f3e2e5849f917853984c69bf02a0f1e27c..26882e165c9e37a105f988020031f03d6b1a5cf9 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -135,18 +135,23 @@ static bool ip6_parse_tlv(const struct tlvtype_proc *procs,
 	len -= 2;
 
 	while (len > 0) {
-		int optlen = nh[off + 1] + 2;
-		int i;
+		int optlen, i;
 
-		switch (nh[off]) {
-		case IPV6_TLV_PAD1:
-			optlen = 1;
+		if (nh[off] == IPV6_TLV_PAD1) {
 			padlen++;
 			if (padlen > 7)
 				goto bad;
-			break;
+			off++;
+			len--;
+			continue;
+		}
+		if (len < 2)
+			goto bad;
+		optlen = nh[off + 1] + 2;
+		if (optlen > len)
+			goto bad;
 
-		case IPV6_TLV_PADN:
+		if (nh[off] == IPV6_TLV_PADN) {
 			/* RFC 2460 states that the purpose of PadN is
 			 * to align the containing header to multiples
 			 * of 8. 7 is therefore the highest valid value.
@@ -163,12 +168,7 @@ static bool ip6_parse_tlv(const struct tlvtype_proc *procs,
 				if (nh[off + i] != 0)
 					goto bad;
 			}
-			break;
-
-		default: /* Other TLV code so scan list */
-			if (optlen > len)
-				goto bad;
-
+		} else {
 			tlv_count++;
 			if (tlv_count > max_count)
 				goto bad;
@@ -188,7 +188,6 @@ static bool ip6_parse_tlv(const struct tlvtype_proc *procs,
 				return false;
 
 			padlen = 0;
-			break;
 		}
 		off += optlen;
 		len -= optlen;
-- 
2.32.0.288.g62a8d224e6-goog


^ permalink raw reply related	[flat|nested] 3+ messages in thread

* Re: [PATCH v2 net] ipv6: fix out-of-bound access in ip6_parse_tlv()
  2021-06-24 10:07 [PATCH v2 net] ipv6: fix out-of-bound access in ip6_parse_tlv() Eric Dumazet
@ 2021-06-24 13:15 ` Paolo Abeni
  2021-06-24 19:50 ` patchwork-bot+netdevbpf
  1 sibling, 0 replies; 3+ messages in thread
From: Paolo Abeni @ 2021-06-24 13:15 UTC (permalink / raw)
  To: Eric Dumazet, David S . Miller, Jakub Kicinski
  Cc: netdev, Eric Dumazet, Tom Herbert

On Thu, 2021-06-24 at 03:07 -0700, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> First problem is that optlen is fetched without checking
> there is more than one byte to parse.
> 
> Fix this by taking care of IPV6_TLV_PAD1 before
> fetching optlen (under appropriate sanity checks against len)
> 
> Second problem is that IPV6_TLV_PADN checks of zero
> padding are performed before the check of remaining length.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Fixes: c1412fce7ecc ("net/ipv6/exthdrs.c: Strict PadN option checking")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: Tom Herbert <tom@herbertland.com>
> ---
> v2: Removed not needed optlen assignment for IPV6_TLV_PAD1 handling,
>     added the Fixes: tag for first problem, feedback from Paolo, thanks !
> 
>  net/ipv6/exthdrs.c | 27 +++++++++++++--------------
>  1 file changed, 13 insertions(+), 14 deletions(-)
> 
> diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
> index 6f7da8f3e2e5849f917853984c69bf02a0f1e27c..26882e165c9e37a105f988020031f03d6b1a5cf9 100644
> --- a/net/ipv6/exthdrs.c
> +++ b/net/ipv6/exthdrs.c
> @@ -135,18 +135,23 @@ static bool ip6_parse_tlv(const struct tlvtype_proc *procs,
>  	len -= 2;
>  
>  	while (len > 0) {
> -		int optlen = nh[off + 1] + 2;
> -		int i;
> +		int optlen, i;
>  
> -		switch (nh[off]) {
> -		case IPV6_TLV_PAD1:
> -			optlen = 1;
> +		if (nh[off] == IPV6_TLV_PAD1) {
>  			padlen++;
>  			if (padlen > 7)
>  				goto bad;
> -			break;
> +			off++;
> +			len--;
> +			continue;
> +		}
> +		if (len < 2)
> +			goto bad;
> +		optlen = nh[off + 1] + 2;
> +		if (optlen > len)
> +			goto bad;
>  
> -		case IPV6_TLV_PADN:
> +		if (nh[off] == IPV6_TLV_PADN) {
>  			/* RFC 2460 states that the purpose of PadN is
>  			 * to align the containing header to multiples
>  			 * of 8. 7 is therefore the highest valid value.
> @@ -163,12 +168,7 @@ static bool ip6_parse_tlv(const struct tlvtype_proc *procs,
>  				if (nh[off + i] != 0)
>  					goto bad;
>  			}
> -			break;
> -
> -		default: /* Other TLV code so scan list */
> -			if (optlen > len)
> -				goto bad;
> -
> +		} else {
>  			tlv_count++;
>  			if (tlv_count > max_count)
>  				goto bad;
> @@ -188,7 +188,6 @@ static bool ip6_parse_tlv(const struct tlvtype_proc *procs,
>  				return false;
>  
>  			padlen = 0;
> -			break;
>  		}
>  		off += optlen;
>  		len -= optlen;

LGTM!

Reviewd-by: Paolo Abeni <pabeni@redhat.com>


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH v2 net] ipv6: fix out-of-bound access in ip6_parse_tlv()
  2021-06-24 10:07 [PATCH v2 net] ipv6: fix out-of-bound access in ip6_parse_tlv() Eric Dumazet
  2021-06-24 13:15 ` Paolo Abeni
@ 2021-06-24 19:50 ` patchwork-bot+netdevbpf
  1 sibling, 0 replies; 3+ messages in thread
From: patchwork-bot+netdevbpf @ 2021-06-24 19:50 UTC (permalink / raw)
  To: Eric Dumazet; +Cc: davem, kuba, netdev, edumazet, pabeni, tom

Hello:

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

On Thu, 24 Jun 2021 03:07:20 -0700 you wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> First problem is that optlen is fetched without checking
> there is more than one byte to parse.
> 
> Fix this by taking care of IPV6_TLV_PAD1 before
> fetching optlen (under appropriate sanity checks against len)
> 
> [...]

Here is the summary with links:
  - [v2,net] ipv6: fix out-of-bound access in ip6_parse_tlv()
    https://git.kernel.org/netdev/net/c/624085a31c1a

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html



^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2021-06-24 19:50 UTC | newest]

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2021-06-24 10:07 [PATCH v2 net] ipv6: fix out-of-bound access in ip6_parse_tlv() Eric Dumazet
2021-06-24 13:15 ` Paolo Abeni
2021-06-24 19:50 ` patchwork-bot+netdevbpf

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