* [PATCH net] ip: in cmsg IP(V6)_ORIGDSTADDR do not read beyond headlen
@ 2018-07-23 0:43 Willem de Bruijn
2018-07-23 1:43 ` Eric Dumazet
0 siblings, 1 reply; 3+ messages in thread
From: Willem de Bruijn @ 2018-07-23 0:43 UTC (permalink / raw)
To: netdev; +Cc: davem, Willem de Bruijn
From: Willem de Bruijn <willemb@google.com>
Syzbot reported a read beyond the end of the skb head when returning
IPV6_ORIGDSTADDR:
BUG: KMSAN: kernel-infoleak in put_cmsg+0x5ef/0x860 net/core/scm.c:242
CPU: 0 PID: 4501 Comm: syz-executor128 Not tainted 4.17.0+ #9
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x185/0x1d0 lib/dump_stack.c:113
kmsan_report+0x188/0x2a0 mm/kmsan/kmsan.c:1125
kmsan_internal_check_memory+0x138/0x1f0 mm/kmsan/kmsan.c:1219
kmsan_copy_to_user+0x7a/0x160 mm/kmsan/kmsan.c:1261
copy_to_user include/linux/uaccess.h:184 [inline]
put_cmsg+0x5ef/0x860 net/core/scm.c:242
ip6_datagram_recv_specific_ctl+0x1cf3/0x1eb0 net/ipv6/datagram.c:719
ip6_datagram_recv_ctl+0x41c/0x450 net/ipv6/datagram.c:733
rawv6_recvmsg+0x10fb/0x1460 net/ipv6/raw.c:521
[..]
This logic and its ipv4 counterpart read the destination port from
the packet at skb_transport_offset(skb) + 4.
With MSG_MORE and a local SOCK_RAW sender, syzbot was able to cook a
packet that stores headers exactly up to skb_transport_offset(skb) in
the head and the remainder in a frag.
Avoid reading beyond skb->tail by testing skb_headlen(skb) instead of
skb->len when trying to access this field.
Link: http://lkml.kernel.org/r/CAF=yD-LEJwZj5a1-bAAj2Oy_hKmGygV6rsJ_WOrAYnv-fnayiQ@mail.gmail.com
Reported-by: syzbot+9adb4b567003cac781f0@syzkaller.appspotmail.com
Signed-off-by: Willem de Bruijn <willemb@google.com>
---
net/ipv4/ip_sockglue.c | 2 +-
net/ipv6/datagram.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 64c76dcf7386..5f228d641d9b 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -152,7 +152,7 @@ static void ip_cmsg_recv_dstaddr(struct msghdr *msg, struct sk_buff *skb)
const struct iphdr *iph = ip_hdr(skb);
__be16 *ports = (__be16 *)skb_transport_header(skb);
- if (skb_transport_offset(skb) + 4 > (int)skb->len)
+ if (skb_transport_offset(skb) + 4 > (int)skb_headlen(skb))
return;
/* All current transport protocols have the port numbers in the
diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
index 2ee08b6a86a4..fd43810aacd2 100644
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -702,7 +702,7 @@ void ip6_datagram_recv_specific_ctl(struct sock *sk, struct msghdr *msg,
struct sockaddr_in6 sin6;
__be16 *ports = (__be16 *) skb_transport_header(skb);
- if (skb_transport_offset(skb) + 4 <= (int)skb->len) {
+ if (skb_transport_offset(skb) + 4 <= (int)skb_headlen(skb)) {
/* All current transport protocols have the port numbers in the
* first four bytes of the transport header and this function is
* written with this assumption in mind.
--
2.18.0.233.g985f88cf7e-goog
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH net] ip: in cmsg IP(V6)_ORIGDSTADDR do not read beyond headlen
2018-07-23 0:43 [PATCH net] ip: in cmsg IP(V6)_ORIGDSTADDR do not read beyond headlen Willem de Bruijn
@ 2018-07-23 1:43 ` Eric Dumazet
2018-07-23 2:01 ` Willem de Bruijn
0 siblings, 1 reply; 3+ messages in thread
From: Eric Dumazet @ 2018-07-23 1:43 UTC (permalink / raw)
To: Willem de Bruijn, netdev; +Cc: davem, Willem de Bruijn
On 07/22/2018 05:43 PM, Willem de Bruijn wrote:
> From: Willem de Bruijn <willemb@google.com>
>
> Syzbot reported a read beyond the end of the skb head when returning
> IPV6_ORIGDSTADDR:
>
> BUG: KMSAN: kernel-infoleak in put_cmsg+0x5ef/0x860 net/core/scm.c:242
> CPU: 0 PID: 4501 Comm: syz-executor128 Not tainted 4.17.0+ #9
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
> __dump_stack lib/dump_stack.c:77 [inline]
> dump_stack+0x185/0x1d0 lib/dump_stack.c:113
> kmsan_report+0x188/0x2a0 mm/kmsan/kmsan.c:1125
> kmsan_internal_check_memory+0x138/0x1f0 mm/kmsan/kmsan.c:1219
> kmsan_copy_to_user+0x7a/0x160 mm/kmsan/kmsan.c:1261
> copy_to_user include/linux/uaccess.h:184 [inline]
> put_cmsg+0x5ef/0x860 net/core/scm.c:242
> ip6_datagram_recv_specific_ctl+0x1cf3/0x1eb0 net/ipv6/datagram.c:719
> ip6_datagram_recv_ctl+0x41c/0x450 net/ipv6/datagram.c:733
> rawv6_recvmsg+0x10fb/0x1460 net/ipv6/raw.c:521
> [..]
>
> This logic and its ipv4 counterpart read the destination port from
> the packet at skb_transport_offset(skb) + 4.
>
> With MSG_MORE and a local SOCK_RAW sender, syzbot was able to cook a
> packet that stores headers exactly up to skb_transport_offset(skb) in
> the head and the remainder in a frag.
>
> Avoid reading beyond skb->tail by testing skb_headlen(skb) instead of
> skb->len when trying to access this field.
>
> Link: http://lkml.kernel.org/r/CAF=yD-LEJwZj5a1-bAAj2Oy_hKmGygV6rsJ_WOrAYnv-fnayiQ@mail.gmail.com
> Reported-by: syzbot+9adb4b567003cac781f0@syzkaller.appspotmail.com
> Signed-off-by: Willem de Bruijn <willemb@google.com>
> ---
> net/ipv4/ip_sockglue.c | 2 +-
> net/ipv6/datagram.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
> index 64c76dcf7386..5f228d641d9b 100644
> --- a/net/ipv4/ip_sockglue.c
> +++ b/net/ipv4/ip_sockglue.c
> @@ -152,7 +152,7 @@ static void ip_cmsg_recv_dstaddr(struct msghdr *msg, struct sk_buff *skb)
> const struct iphdr *iph = ip_hdr(skb);
> __be16 *ports = (__be16 *)skb_transport_header(skb);
>
> - if (skb_transport_offset(skb) + 4 > (int)skb->len)
> + if (skb_transport_offset(skb) + 4 > (int)skb_headlen(skb))
> return;
>
This really should call pskb_may_pull() or skb_header_pointer().
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH net] ip: in cmsg IP(V6)_ORIGDSTADDR do not read beyond headlen
2018-07-23 1:43 ` Eric Dumazet
@ 2018-07-23 2:01 ` Willem de Bruijn
0 siblings, 0 replies; 3+ messages in thread
From: Willem de Bruijn @ 2018-07-23 2:01 UTC (permalink / raw)
To: Eric Dumazet; +Cc: Network Development, David Miller, Willem de Bruijn
On Sun, Jul 22, 2018 at 9:43 PM Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
>
>
> On 07/22/2018 05:43 PM, Willem de Bruijn wrote:
> > From: Willem de Bruijn <willemb@google.com>
> >
> > Syzbot reported a read beyond the end of the skb head when returning
> > IPV6_ORIGDSTADDR:
> >
> > BUG: KMSAN: kernel-infoleak in put_cmsg+0x5ef/0x860 net/core/scm.c:242
> > CPU: 0 PID: 4501 Comm: syz-executor128 Not tainted 4.17.0+ #9
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > Call Trace:
> > __dump_stack lib/dump_stack.c:77 [inline]
> > dump_stack+0x185/0x1d0 lib/dump_stack.c:113
> > kmsan_report+0x188/0x2a0 mm/kmsan/kmsan.c:1125
> > kmsan_internal_check_memory+0x138/0x1f0 mm/kmsan/kmsan.c:1219
> > kmsan_copy_to_user+0x7a/0x160 mm/kmsan/kmsan.c:1261
> > copy_to_user include/linux/uaccess.h:184 [inline]
> > put_cmsg+0x5ef/0x860 net/core/scm.c:242
> > ip6_datagram_recv_specific_ctl+0x1cf3/0x1eb0 net/ipv6/datagram.c:719
> > ip6_datagram_recv_ctl+0x41c/0x450 net/ipv6/datagram.c:733
> > rawv6_recvmsg+0x10fb/0x1460 net/ipv6/raw.c:521
> > [..]
> >
> > This logic and its ipv4 counterpart read the destination port from
> > the packet at skb_transport_offset(skb) + 4.
> >
> > With MSG_MORE and a local SOCK_RAW sender, syzbot was able to cook a
> > packet that stores headers exactly up to skb_transport_offset(skb) in
> > the head and the remainder in a frag.
> >
> > Avoid reading beyond skb->tail by testing skb_headlen(skb) instead of
> > skb->len when trying to access this field.
> >
> > Link: http://lkml.kernel.org/r/CAF=yD-LEJwZj5a1-bAAj2Oy_hKmGygV6rsJ_WOrAYnv-fnayiQ@mail.gmail.com
> > Reported-by: syzbot+9adb4b567003cac781f0@syzkaller.appspotmail.com
> > Signed-off-by: Willem de Bruijn <willemb@google.com>
> > ---
> > net/ipv4/ip_sockglue.c | 2 +-
> > net/ipv6/datagram.c | 2 +-
> > 2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
> > index 64c76dcf7386..5f228d641d9b 100644
> > --- a/net/ipv4/ip_sockglue.c
> > +++ b/net/ipv4/ip_sockglue.c
> > @@ -152,7 +152,7 @@ static void ip_cmsg_recv_dstaddr(struct msghdr *msg, struct sk_buff *skb)
> > const struct iphdr *iph = ip_hdr(skb);
> > __be16 *ports = (__be16 *)skb_transport_header(skb);
> >
> > - if (skb_transport_offset(skb) + 4 > (int)skb->len)
> > + if (skb_transport_offset(skb) + 4 > (int)skb_headlen(skb))
> > return;
> >
>
> This really should call pskb_may_pull() or skb_header_pointer().
Okay. Since in all common cases these bytes do lie in the skb head,
pskb_may_pull is pretty cheap. I'll use that. The linked discussion
already outlines a rough patch.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-07-23 0:43 [PATCH net] ip: in cmsg IP(V6)_ORIGDSTADDR do not read beyond headlen Willem de Bruijn
2018-07-23 1:43 ` Eric Dumazet
2018-07-23 2:01 ` Willem de Bruijn
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