[PATCH 5.16 066/285] dm ioctl: prevent potential spectre v1 gadget

Greg Kroah-Hartman
2022-04-12T07:50:01Z

From: Jordy Zomer <jordy@jordyzomer.github.io>

[ Upstream commit cd9c88da171a62c4b0f1c70e50c75845969fbc18 ]

It appears like cmd could be a Spectre v1 gadget as it's supplied by a
user and used as an array index. Prevent the contents of kernel memory
from being leaked to userspace via speculative execution by using
array_index_nospec.

Signed-off-by: Jordy Zomer <jordy@pwning.systems>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/md/dm-ioctl.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 21fe8652b095..901abd6dea41 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -18,6 +18,7 @@
#include <linux/dm-ioctl.h>
#include <linux/hdreg.h>
#include <linux/compat.h>
+#include <linux/nospec.h>

#include <linux/uaccess.h>
#include <linux/ima.h>
@@ -1788,6 +1789,7 @@ static ioctl_fn lookup_ioctl(unsigned int cmd, int *ioctl_flags)
if (unlikely(cmd >= ARRAY_SIZE(_ioctls)))
return NULL;

+ cmd = array_index_nospec(cmd, ARRAY_SIZE(_ioctls));
*ioctl_flags = _ioctls[cmd].flags;
return _ioctls[cmd].fn;
}
--
2.35.1