[PATCH 14/18] ipv4: prevent bounds-check bypass via speculative execution

Dan Williams
2018-01-06T01:19:24Z

Static analysis reports that 'offset' may be a user controlled value
that is used as a data dependency reading from a raw_frag_vec buffer.
In order to avoid potential leaks of kernel memory values, block
speculative execution of the instruction stream that could issue further
reads based on an invalid '*(rfv->c + offset)' value.

Based on an original patch by Elena Reshetova.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: netdev@vger.kernel.org
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
net/ipv4/raw.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index 125c1eab3eaa..f72b20131a15 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -57,6 +57,7 @@
#include <linux/in_route.h>
#include <linux/route.h>
#include <linux/skbuff.h>
+#include <linux/compiler.h>
#include <linux/igmp.h>
#include <net/net_namespace.h>
#include <net/dst.h>
@@ -472,17 +473,17 @@ static int raw_getfrag(void *from, char *to, int offset, int len, int odd,
struct sk_buff *skb)
{
struct raw_frag_vec *rfv = from;
+ char *rfv_buf;

- if (offset < rfv->hlen) {
+ if ((rfv_buf = nospec_array_ptr(rfv->hdr.c, offset, rfv->hlen))) {
int copy = min(rfv->hlen - offset, len);

if (skb->ip_summed == CHECKSUM_PARTIAL)
- memcpy(to, rfv->hdr.c + offset, copy);
+ memcpy(to, rfv_buf, copy);
else
skb->csum = csum_block_add(
skb->csum,
- csum_partial_copy_nocheck(rfv->hdr.c + offset,
- to, copy, 0),
+ csum_partial_copy_nocheck(rfv_buf, to, copy, 0),
odd);

odd = 0;