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FAILED: patch "[PATCH] block: fix use-after-free in disk_part_iter_next" failed to apply to 5.10-stable tree

PATCH [email protected] 1 participant 1 message Jan 11, 2021

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The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From aebf5db917055b38f4945ed6d621d9f07a44ff30 Mon Sep 17 00:00:00 2001
From: Ming Lei <[email protected]>
Date: Mon, 21 Dec 2020 12:33:35 +0800
Subject: [PATCH] block: fix use-after-free in disk_part_iter_next

Make sure that bdgrab() is done on the 'block_device' instance before referring to it for avoiding use-after-free.

Cc <[email protected]>
Reported-by [email protected]
Signed-off-by Ming Lei <[email protected]>
Reviewed-by Christoph Hellwig <[email protected]>
Signed-off-by Jens Axboe <[email protected]>
block/genhd.c +7 -4
index 73faec438e49..419548e92d82 100644
@@ -246,15 +246,18 @@ struct block_device *disk_part_iter_next(struct disk_part_iter *piter)
 		part = rcu_dereference(ptbl->part[piter->idx]);
 		if (!part)
 			continue;
+		piter->part = bdgrab(part);
+		if (!piter->part)
+			continue;
 		if (!bdev_nr_sectors(part) &&
 		    !(piter->flags & DISK_PITER_INCL_EMPTY) &&
 		    !(piter->flags & DISK_PITER_INCL_EMPTY_PART0 &&
-		      piter->idx == 0))
+		      piter->idx == 0)) {
+			bdput(piter->part);
+			piter->part = NULL;
 			continue;
+		}
 
-		piter->part = bdgrab(part);
-		if (!piter->part)
-			continue;
 		piter->idx += inc;
 		break;
 	}