From: Yangxi Xiang <xyangxi5@gmail.com>
Date: Tue, 28 Jun 2022 17:33:22 +0800
Subject: vt: fix memory overlapping when deleting chars in the buffer
Git-commit: 39cdb68c64d84e71a4a717000b6e5de208ee60cc
Patch-mainline: 5.19-rc7
References: bsc#1220845 CVE-2022-48627

A memory overlapping copy occurs when deleting a long line. This memory
overlapping copy can cause data corruption when scr_memcpyw is optimized
to memcpy because memcpy does not ensure its behavior if the destination
buffer overlaps with the source buffer. The line buffer is not always
broken, because the memcpy utilizes the hardware acceleration, whose
result is not deterministic.

Fix this problem by using replacing the scr_memcpyw with scr_memmovew.

Fixes: 81732c3b2fed ("tty vt: Fix line garbage in virtual console on command line edition")
Cc: stable <stable@kernel.org>
Signed-off-by: Yangxi Xiang <xyangxi5@gmail.com>
Link: https://lore.kernel.org/r/20220628093322.5688-1-xyangxi5@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/tty/vt/vt.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -543,7 +543,7 @@ static void delete_char(struct vc_data *
 {
 	unsigned short *p = (unsigned short *) vc->vc_pos;
 
-	scr_memcpyw(p, p + nr, (vc->vc_cols - vc->vc_x - nr) * 2);
+	scr_memmovew(p, p + nr, (vc->vc_cols - vc->vc_x - nr) * 2);
 	scr_memsetw(p + vc->vc_cols - vc->vc_x - nr, vc->vc_video_erase_char,
 			nr * 2);
 	vc->vc_need_wrap = 0;