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vt: fix memory overlapping when deleting chars in the buffer

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commit 39cdb68c64 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: 81732c3b2f ("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 fc7dfe3d12
commit c8686c014b
1 changed files with 1 additions and 1 deletions
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drivers/tty/vt/vt.c
+1 -1
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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;