ip6_gre: fix ip6gre_err() invalid reads
authorEric Dumazet <edumazet@google.com>
Sun, 5 Feb 2017 07:18:55 +0000 (23:18 -0800)
committerDavid S. Miller <davem@davemloft.net>
Sun, 5 Feb 2017 22:23:04 +0000 (17:23 -0500)
commit7892032cfe67f4bde6fc2ee967e45a8fbaf33756
treecbadc1cb0484fbdcd3d5d68d5189c1d022d0d0d4
parentd71b7896886345c53ef1d84bda2bc758554f5d61
ip6_gre: fix ip6gre_err() invalid reads

Andrey Konovalov reported out of bound accesses in ip6gre_err()

If GRE flags contains GRE_KEY, the following expression
*(((__be32 *)p) + (grehlen / 4) - 1)

accesses data ~40 bytes after the expected point, since
grehlen includes the size of IPv6 headers.

Let's use a "struct gre_base_hdr *greh" pointer to make this
code more readable.

p[1] becomes greh->protocol.
grhlen is the GRE header length.

Fixes: c12b395a4664 ("gre: Support GRE over IPv6")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/ipv6/ip6_gre.c