c3b4c3a47e
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: 8d79266bc48c ("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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.