tree c73c7e79c25024f6865f8e349789ac62d66776b8
parent 3e59cb0ddfd2c59991f38e89352ad8a3c71b2374
author Eric Dumazet <edumazet@google.com> 1368808623 +0000
committer David S. Miller <davem@davemloft.net> 1369032941 -0700

x86: bpf_jit_comp: secure bpf jit against spraying attacks

hpa bringed into my attention some security related issues
with BPF JIT on x86.

This patch makes sure the bpf generated code is marked read only,
as other kernel text sections.

It also splits the unused space (we vmalloc() and only use a fraction of
the page) in two parts, so that the generated bpf code not starts at a
known offset in the page, but a pseudo random one.

Refs:
http://mainisusuallyafunction.blogspot.com/2012/11/attacking-hardened-linux-systems-with.html

Reported-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>