This is a note to let you know that I've just added the patch titled
vt: fix memory overlapping when deleting chars in the buffer
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
vt-fix-memory-overlapping-when-deleting-chars-in-the-buffer.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 39cdb68c64d84e71a4a717000b6e5de208ee60cc Mon Sep 17 00:00:00 2001
From: Yangxi Xiang <xyangxi5@xxxxxxxxx>
Date: Tue, 28 Jun 2022 17:33:22 +0800
Subject: vt: fix memory overlapping when deleting chars in the buffer
From: Yangxi Xiang <xyangxi5@xxxxxxxxx>
commit 39cdb68c64d84e71a4a717000b6e5de208ee60cc upstream.
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@xxxxxxxxxx>
Signed-off-by: Yangxi Xiang <xyangxi5@xxxxxxxxx>
Link: https://lore.kernel.org/r/20220628093322.5688-1-xyangxi5@xxxxxxxxx
[ KN: vc_state is not a separate structure in LTS v4.19, v5.4. Adjusted the patch
accordingly by using vc_x instead of state.x for backport. ]
Signed-off-by: Kuntal Nayak <kuntal.nayak@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -855,7 +855,7 @@ static void delete_char(struct vc_data *
unsigned short *p = (unsigned short *) vc->vc_pos;
vc_uniscr_delete(vc, nr);
- 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;
Patches currently in stable-queue which might be from xyangxi5@xxxxxxxxx are
queue-5.4/vt-fix-memory-overlapping-when-deleting-chars-in-the-buffer.patch
