vt: fix unicode buffer corruption when deleting characters

jira LE-1907
cve CVE-2024-35823
Rebuild_History Non-Buildable kernel-5.14.0-427.31.1.el9_4
commit-author Nicolas Pitre <[email protected]>
commit 1581daf

This is the same issue that was fixed for the VGA text buffer in commit
39cdb68 ("vt: fix memory overlapping when deleting chars in the
buffer"). The cure is also the same i.e. replace memcpy() with memmove()
due to the overlaping buffers.

	Signed-off-by: Nicolas Pitre <[email protected]>
Fixes: 81732c3 ("tty vt: Fix line garbage in virtual console on command line edition")
	Cc: stable <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
	Signed-off-by: Greg Kroah-Hartman <[email protected]>
(cherry picked from commit 1581daf)
	Signed-off-by: Jonathan Maple <[email protected]>

Author: PlaidCat

drivers/tty/vt/vt.c

@@ -398,7 +398,7 @@ static void vc_uniscr_delete(struct vc_data *vc, unsigned int nr)
 		char32_t *ln = uniscr->lines[vc->state.y];
 		unsigned int x = vc->state.x, cols = vc->vc_cols;
 
-		memcpy(&ln[x], &ln[x + nr], (cols - x - nr) * sizeof(*ln));
+		memmove(&ln[x], &ln[x + nr], (cols - x - nr) * sizeof(*ln));
 		memset32(&ln[cols - nr], ' ', nr);
 	}
 }