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>
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@ -855,7 +855,7 @@ static void delete_char(struct vc_data *vc, unsigned int nr)
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unsigned short *p = (unsigned short *) vc->vc_pos;
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vc_uniscr_delete(vc, nr);
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scr_memcpyw(p, p + nr, (vc->vc_cols - vc->state.x - nr) * 2);
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scr_memmovew(p, p + nr, (vc->vc_cols - vc->state.x - nr) * 2);
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scr_memsetw(p + vc->vc_cols - vc->state.x - nr, vc->vc_video_erase_char,
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nr * 2);
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vc->vc_need_wrap = 0;
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