badblocks: avoid checking invalid range in badblocks_check()

If prev_badblocks() returns '-1', it means no valid badblocks record
before the checking range. It doesn't make sense to check whether
the input checking range is overlapped with the non-existed invalid
front range.

This patch checkes whether 'prev >= 0' is true before calling
overlap_front(), to void such invalid operations.

Fixes: 3ea3354 ("badblocks: improve badblocks_check() for multiple ranges handling")
Reported-and-tested-by: Ira Weiny <[email protected]>
Signed-off-by: Coly Li <[email protected]>
Link: https://lore.kernel.org/nvdimm/[email protected]/
Cc: Dan Williams <[email protected]>
Cc: Geliang Tang <[email protected]>
Cc: Hannes Reinecke <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: NeilBrown <[email protected]>
Cc: Vishal L Verma <[email protected]>
Cc: Xiao Ni <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: Coly Li

block/badblocks.c

@@ -1312,12 +1312,14 @@ static int _badblocks_check(struct badblocks *bb, sector_t s, int sectors,
 	prev = prev_badblocks(bb, &bad, hint);
 
 	/* start after all badblocks */
-	if ((prev + 1) >= bb->count && !overlap_front(bb, prev, &bad)) {
+	if ((prev >= 0) &&
+	    ((prev + 1) >= bb->count) && !overlap_front(bb, prev, &bad)) {
 		len = sectors;
 		goto update_sectors;
 	}
 
-	if (overlap_front(bb, prev, &bad)) {
+	/* Overlapped with front badblocks record */
+	if ((prev >= 0) && overlap_front(bb, prev, &bad)) {
 		if (BB_ACK(p[prev]))
 			acked_badblocks++;
 		else