[PATCH 4.9 10/70] IB/rxe: do not copy extra stack memory to skb

Greg Kroah-Hartman
2018-09-17T22:57:54Z

From: Kees Cook <keescook@chromium.org>

commit 4c93496f18ce5044d78e4f7f9e018682a4f44b3d upstream.

This fixes a over-read condition detected by FORTIFY_SOURCE for this
line:

memcpy(SKB_TO_PKT(skb), &ack_pkt, sizeof(skb->cb));

The error was:

In file included from ./include/linux/bitmap.h:8:0,
from ./include/linux/cpumask.h:11,
from ./include/linux/mm_types_task.h:13,
from ./include/linux/mm_types.h:4,
from ./include/linux/kmemcheck.h:4,
from ./include/linux/skbuff.h:18,
from drivers/infiniband/sw/rxe/rxe_resp.c:34:
In function 'memcpy',
inlined from 'send_atomic_ack.constprop' at drivers/infiniband/sw/rxe/rxe_resp.c:998:2,
inlined from 'acknowledge' at drivers/infiniband/sw/rxe/rxe_resp.c:1026:3,
inlined from 'rxe_responder' at drivers/infiniband/sw/rxe/rxe_resp.c:1286:10:
./include/linux/string.h:309:4: error: call to '__read_overflow2' declared with attribute error: detected read beyond size of object passed as 2nd parameter
__read_overflow2();

Daniel Micay noted that struct rxe_pkt_info is 32 bytes on 32-bit
architectures, but skb->cb is still 64. The memcpy() over-reads 32
bytes. This fixes it by zeroing the unused bytes in skb->cb.

Link: http://lkml.kernel.org/r/1497903987-21002-5-git-send-email-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Moni Shoua <monis@mellanox.com>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Sean Hefty <sean.hefty@intel.com>
Cc: Daniel Micay <danielmicay@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/infiniband/sw/rxe/rxe_resp.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/infiniband/sw/rxe/rxe_resp.c
+++ b/drivers/infiniband/sw/rxe/rxe_resp.c
@@ -978,7 +978,9 @@ static int send_atomic_ack(struct rxe_qp
free_rd_atomic_resource(qp, res);
rxe_advance_resp_resource(qp);

- memcpy(SKB_TO_PKT(skb), &ack_pkt, sizeof(skb->cb));
+ memcpy(SKB_TO_PKT(skb), &ack_pkt, sizeof(ack_pkt));
+ memset((unsigned char *)SKB_TO_PKT(skb) + sizeof(ack_pkt), 0,
+ sizeof(skb->cb) - sizeof(ack_pkt));

res->type = RXE_ATOMIC_MASK;
res->atomic.skb = skb;