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vt: fix memory overlapping when deleting chars in the buffer

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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@kernel.org>
Signed-off-by: Yangxi Xiang <xyangxi5@gmail.com>
Link: https://lore.kernel.org/r/20220628093322.5688-1-xyangxi5@gmail.com
[ 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@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Yangxi Xiang 2022-06-28 17:33:22 +08:00 committed by Greg Kroah-Hartman
parent d6077e0d38
commit 815be99d93
1 changed files with 1 additions and 1 deletions
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2
drivers/tty/vt/vt.c
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@ -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->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;