The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 39cdb68c64d84e71a4a717000b6e5de208ee60cc Mon Sep 17 00:00:00 2001 From: Yangxi Xiang xyangxi5@gmail.com Date: Tue, 28 Jun 2022 17:33:22 +0800 Subject: [PATCH] vt: fix memory overlapping when deleting chars in the buffer

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

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index f8c87c4d7399..dfc1f4b445f3 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -855,7 +855,7 @@ static void delete_char(struct vc_data *vc, unsigned int nr) unsigned short *p = (unsigned short *) vc->vc_pos;

vc_uniscr_delete(vc, nr); - scr_memcpyw(p, p + nr, (vc->vc_cols - vc->state.x - nr) * 2); + scr_memmovew(p, p + nr, (vc->vc_cols - vc->state.x - nr) * 2); scr_memsetw(p + vc->vc_cols - vc->state.x - nr, vc->vc_video_erase_char, nr * 2); vc->vc_need_wrap = 0;