From cd9c88da171a62c4b0f1c70e50c75845969fbc18 Mon Sep 17 00:00:00 2001
From: Jordy Zomer <jordy@jordyzomer.github.io>
Date: Sat, 29 Jan 2022 15:58:39 +0100
Subject: [PATCH] dm ioctl: prevent potential spectre v1 gadget
Git-commit: cd9c88da171a62c4b0f1c70e50c75845969fbc18
Patch-mainline: v5.18-rc1
References: git-fixes

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.

(Coly Li: refreshed for Linux v4.12 based SUSE kernel)

Signed-off-by: Jordy Zomer <jordy@pwning.systems>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Coly Li <colyli@suse.de>

---
 drivers/md/dm-ioctl.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -17,6 +17,7 @@
 #include <linux/dm-ioctl.h>
 #include <linux/hdreg.h>
 #include <linux/compat.h>
+#include <linux/nospec.h>
 
 #include <linux/uaccess.h>
 
@@ -1670,6 +1671,7 @@ static ioctl_fn lookup_ioctl(unsigned in
 	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;
 }