5.4-stable review patch. If anyone has any objections, please let me know.
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From: Yangxi Xiang xyangxi5@gmail.com
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 --- drivers/tty/vt/vt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -855,7 +855,7 @@ static void delete_char(struct vc_data * 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;