linux/net/xfrm
Hangbin Liu c3b4c3a47e xfrm/xfrm_policy: fix dst dev null pointer dereference in collect_md mode
In decode_session{4,6} there is a possibility that the skb dst dev is NULL,
e,g, with tunnel collect_md mode, which will cause kernel crash.
Here is what the code path looks like, for GRE:

- ip6gre_tunnel_xmit
  - ip6gre_xmit_ipv6
    - __gre6_xmit
      - ip6_tnl_xmit
        - if skb->len - t->tun_hlen - eth_hlen > mtu; return -EMSGSIZE
    - icmpv6_send
      - icmpv6_route_lookup
        - xfrm_decode_session_reverse
          - decode_session4
            - oif = skb_dst(skb)->dev->ifindex; <-- here
          - decode_session6
            - oif = skb_dst(skb)->dev->ifindex; <-- here

The reason is __metadata_dst_init() init dst->dev to NULL by default.
We could not fix it in __metadata_dst_init() as there is no dev supplied.
On the other hand, the skb_dst(skb)->dev is actually not needed as we
called decode_session{4,6} via xfrm_decode_session_reverse(), so oif is not
used by: fl4->flowi4_oif = reverse ? skb->skb_iif : oif;

So make a dst dev check here should be clean and safe.

v4: No changes.

v3: No changes.

v2: fix the issue in decode_session{4,6} instead of updating shared dst dev
in {ip_md, ip6}_tunnel_xmit.

Fixes: 8d79266bc4 ("ip6_tunnel: add collect_md mode to IPv6 tunnels")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Tested-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2019-08-24 14:49:35 -07:00
..
Kconfig Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec 2019-07-05 14:58:22 -07:00
Makefile xfrm: Add virtual xfrm interfaces 2018-06-23 16:07:25 +02:00
xfrm_algo.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
xfrm_device.c Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec-next 2019-07-05 15:01:15 -07:00
xfrm_hash.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
xfrm_hash.h xfrm: use complete IPv6 addresses for hash 2018-10-15 10:09:18 +02:00
xfrm_inout.h xfrm: remove input2 indirection from xfrm_mode 2019-04-08 09:14:55 +02:00
xfrm_input.c xfrm: fix bogus WARN_ON with ipv6 2019-06-12 11:01:56 +02:00
xfrm_interface.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-07-08 19:48:57 -07:00
xfrm_ipcomp.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
xfrm_output.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
xfrm_policy.c xfrm/xfrm_policy: fix dst dev null pointer dereference in collect_md mode 2019-08-24 14:49:35 -07:00
xfrm_proc.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
xfrm_replay.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 335 2019-06-05 17:37:06 +02:00
xfrm_state.c xfrm: remove get_mtu indirection from xfrm_type 2019-07-01 06:16:40 +02:00
xfrm_sysctl.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
xfrm_user.c Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec 2019-07-05 14:58:22 -07:00