* [nf-next PATCH v2] netfilter: nft_exthdr: Fix for unsafe packet data read
@ 2021-06-08 9:40 Phil Sutter
2021-06-08 9:43 ` Florian Westphal
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Phil Sutter @ 2021-06-08 9:40 UTC (permalink / raw)
To: Pablo Neira Ayuso; +Cc: netfilter-devel, Florian Westphal
While iterating through an SCTP packet's chunks, skb_header_pointer() is
called for the minimum expected chunk header size. If (that part of) the
skbuff is non-linear, the following memcpy() may read data past
temporary buffer '_sch'. Use skb_copy_bits() instead which does the
right thing in this situation.
Fixes: 133dc203d77df ("netfilter: nft_exthdr: Support SCTP chunks")
Suggested-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Phil Sutter <phil@nwl.cc>
---
Changes since v1:
- skb_copy_bits() call error handling added
---
net/netfilter/nft_exthdr.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
index 1b0579cb62d08..7f705b5c09de8 100644
--- a/net/netfilter/nft_exthdr.c
+++ b/net/netfilter/nft_exthdr.c
@@ -327,7 +327,9 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr,
break;
dest[priv->len / NFT_REG32_SIZE] = 0;
- memcpy(dest, (char *)sch + priv->offset, priv->len);
+ if (skb_copy_bits(pkt->skb, offset + priv->offset,
+ dest, priv->len) < 0)
+ break;
return;
}
offset += SCTP_PAD4(ntohs(sch->length));
--
2.31.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [nf-next PATCH v2] netfilter: nft_exthdr: Fix for unsafe packet data read
2021-06-08 9:40 [nf-next PATCH v2] netfilter: nft_exthdr: Fix for unsafe packet data read Phil Sutter
@ 2021-06-08 9:43 ` Florian Westphal
2021-06-08 9:56 ` Pablo Neira Ayuso
2021-06-08 10:38 ` Pablo Neira Ayuso
2 siblings, 0 replies; 6+ messages in thread
From: Florian Westphal @ 2021-06-08 9:43 UTC (permalink / raw)
To: Phil Sutter; +Cc: Pablo Neira Ayuso, netfilter-devel, Florian Westphal
Phil Sutter <phil@nwl.cc> wrote:
> While iterating through an SCTP packet's chunks, skb_header_pointer() is
> called for the minimum expected chunk header size. If (that part of) the
> skbuff is non-linear, the following memcpy() may read data past
> temporary buffer '_sch'. Use skb_copy_bits() instead which does the
> right thing in this situation.
>
> Fixes: 133dc203d77df ("netfilter: nft_exthdr: Support SCTP chunks")
> Suggested-by: Florian Westphal <fw@strlen.de>
> Signed-off-by: Phil Sutter <phil@nwl.cc>
Reviewed-by: Florian Westphal <fw@strlen.de>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [nf-next PATCH v2] netfilter: nft_exthdr: Fix for unsafe packet data read
2021-06-08 9:40 [nf-next PATCH v2] netfilter: nft_exthdr: Fix for unsafe packet data read Phil Sutter
2021-06-08 9:43 ` Florian Westphal
@ 2021-06-08 9:56 ` Pablo Neira Ayuso
2021-06-08 10:07 ` Florian Westphal
2021-06-08 10:38 ` Pablo Neira Ayuso
2 siblings, 1 reply; 6+ messages in thread
From: Pablo Neira Ayuso @ 2021-06-08 9:56 UTC (permalink / raw)
To: Phil Sutter; +Cc: netfilter-devel, Florian Westphal
On Tue, Jun 08, 2021 at 11:40:57AM +0200, Phil Sutter wrote:
> While iterating through an SCTP packet's chunks, skb_header_pointer() is
> called for the minimum expected chunk header size. If (that part of) the
> skbuff is non-linear, the following memcpy() may read data past
> temporary buffer '_sch'. Use skb_copy_bits() instead which does the
> right thing in this situation.
>
> Fixes: 133dc203d77df ("netfilter: nft_exthdr: Support SCTP chunks")
> Suggested-by: Florian Westphal <fw@strlen.de>
> Signed-off-by: Phil Sutter <phil@nwl.cc>
> ---
> Changes since v1:
> - skb_copy_bits() call error handling added
> ---
> net/netfilter/nft_exthdr.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
> index 1b0579cb62d08..7f705b5c09de8 100644
> --- a/net/netfilter/nft_exthdr.c
> +++ b/net/netfilter/nft_exthdr.c
> @@ -327,7 +327,9 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr,
> break;
>
> dest[priv->len / NFT_REG32_SIZE] = 0;
> - memcpy(dest, (char *)sch + priv->offset, priv->len);
> + if (skb_copy_bits(pkt->skb, offset + priv->offset,
> + dest, priv->len) < 0)
> + break;
Hm, it looks like tcp exthdt matching has the same problem?
> return;
> }
> offset += SCTP_PAD4(ntohs(sch->length));
> --
> 2.31.1
>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [nf-next PATCH v2] netfilter: nft_exthdr: Fix for unsafe packet data read
2021-06-08 9:56 ` Pablo Neira Ayuso
@ 2021-06-08 10:07 ` Florian Westphal
2021-06-08 10:16 ` Pablo Neira Ayuso
0 siblings, 1 reply; 6+ messages in thread
From: Florian Westphal @ 2021-06-08 10:07 UTC (permalink / raw)
To: Pablo Neira Ayuso; +Cc: Phil Sutter, netfilter-devel, Florian Westphal
Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> On Tue, Jun 08, 2021 at 11:40:57AM +0200, Phil Sutter wrote:
> > While iterating through an SCTP packet's chunks, skb_header_pointer() is
> > called for the minimum expected chunk header size. If (that part of) the
> > skbuff is non-linear, the following memcpy() may read data past
> > temporary buffer '_sch'. Use skb_copy_bits() instead which does the
> > right thing in this situation.
> >
> > Fixes: 133dc203d77df ("netfilter: nft_exthdr: Support SCTP chunks")
> > Suggested-by: Florian Westphal <fw@strlen.de>
> > Signed-off-by: Phil Sutter <phil@nwl.cc>
> > ---
> > Changes since v1:
> > - skb_copy_bits() call error handling added
> > ---
> > net/netfilter/nft_exthdr.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
> > index 1b0579cb62d08..7f705b5c09de8 100644
> > --- a/net/netfilter/nft_exthdr.c
> > +++ b/net/netfilter/nft_exthdr.c
> > @@ -327,7 +327,9 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr,
> > break;
> >
> > dest[priv->len / NFT_REG32_SIZE] = 0;
> > - memcpy(dest, (char *)sch + priv->offset, priv->len);
> > + if (skb_copy_bits(pkt->skb, offset + priv->offset,
> > + dest, priv->len) < 0)
> > + break;
>
> Hm, it looks like tcp exthdt matching has the same problem?
Tcp exthdr either copies from skb linear area or a on-stack scratch space,
it looks ok to me.
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [nf-next PATCH v2] netfilter: nft_exthdr: Fix for unsafe packet data read
2021-06-08 10:07 ` Florian Westphal
@ 2021-06-08 10:16 ` Pablo Neira Ayuso
0 siblings, 0 replies; 6+ messages in thread
From: Pablo Neira Ayuso @ 2021-06-08 10:16 UTC (permalink / raw)
To: Florian Westphal; +Cc: Phil Sutter, netfilter-devel
On Tue, Jun 08, 2021 at 12:07:54PM +0200, Florian Westphal wrote:
> Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> > On Tue, Jun 08, 2021 at 11:40:57AM +0200, Phil Sutter wrote:
> > > While iterating through an SCTP packet's chunks, skb_header_pointer() is
> > > called for the minimum expected chunk header size. If (that part of) the
> > > skbuff is non-linear, the following memcpy() may read data past
> > > temporary buffer '_sch'. Use skb_copy_bits() instead which does the
> > > right thing in this situation.
> > >
> > > Fixes: 133dc203d77df ("netfilter: nft_exthdr: Support SCTP chunks")
> > > Suggested-by: Florian Westphal <fw@strlen.de>
> > > Signed-off-by: Phil Sutter <phil@nwl.cc>
> > > ---
> > > Changes since v1:
> > > - skb_copy_bits() call error handling added
> > > ---
> > > net/netfilter/nft_exthdr.c | 4 +++-
> > > 1 file changed, 3 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
> > > index 1b0579cb62d08..7f705b5c09de8 100644
> > > --- a/net/netfilter/nft_exthdr.c
> > > +++ b/net/netfilter/nft_exthdr.c
> > > @@ -327,7 +327,9 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr,
> > > break;
> > >
> > > dest[priv->len / NFT_REG32_SIZE] = 0;
> > > - memcpy(dest, (char *)sch + priv->offset, priv->len);
> > > + if (skb_copy_bits(pkt->skb, offset + priv->offset,
> > > + dest, priv->len) < 0)
> > > + break;
> >
> > Hm, it looks like tcp exthdt matching has the same problem?
>
> Tcp exthdr either copies from skb linear area or a on-stack scratch space,
> it looks ok to me.
Indeed, I overlook the nft_tcp_header_pointer() call a few lines before.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [nf-next PATCH v2] netfilter: nft_exthdr: Fix for unsafe packet data read
2021-06-08 9:40 [nf-next PATCH v2] netfilter: nft_exthdr: Fix for unsafe packet data read Phil Sutter
2021-06-08 9:43 ` Florian Westphal
2021-06-08 9:56 ` Pablo Neira Ayuso
@ 2021-06-08 10:38 ` Pablo Neira Ayuso
2 siblings, 0 replies; 6+ messages in thread
From: Pablo Neira Ayuso @ 2021-06-08 10:38 UTC (permalink / raw)
To: Phil Sutter; +Cc: netfilter-devel, Florian Westphal
On Tue, Jun 08, 2021 at 11:40:57AM +0200, Phil Sutter wrote:
> While iterating through an SCTP packet's chunks, skb_header_pointer() is
> called for the minimum expected chunk header size. If (that part of) the
> skbuff is non-linear, the following memcpy() may read data past
> temporary buffer '_sch'. Use skb_copy_bits() instead which does the
> right thing in this situation.
Applied, thanks.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2021-06-08 10:38 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2021-06-08 9:40 [nf-next PATCH v2] netfilter: nft_exthdr: Fix for unsafe packet data read Phil Sutter
2021-06-08 9:43 ` Florian Westphal
2021-06-08 9:56 ` Pablo Neira Ayuso
2021-06-08 10:07 ` Florian Westphal
2021-06-08 10:16 ` Pablo Neira Ayuso
2021-06-08 10:38 ` Pablo Neira Ayuso
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