vt: fix memory overlapping when deleting chars in the buffer

stable inclusion
from stable-v5.10.132
commit bfee93c9a6c395f9aa62268f1cedf64999844926
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5YS3T

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bfee93c9a6c395f9aa62268f1cedf64999844926

--------------------------------

commit 39cdb68c 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: 81732c3b ("tty vt: Fix line garbage in virtual console on command line edition")
Cc: stable <stable@kernel.org>
Signed-off-by: NYangxi Xiang <xyangxi5@gmail.com>
Link: https://lore.kernel.org/r/20220628093322.5688-1-xyangxi5@gmail.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

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;