linux-kernel - [PATCH 5.8 099/232] dm: dont call report zones for more than the user requested

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Date:   Thu, 20 Aug 2020 11:19:10 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Johannes Thumshirn <johannes.thumshirn@....com>,
        Damien Le Moal <damien.lemoal@....com>,
        Mike Snitzer <snitzer@...hat.com>
Subject: [PATCH 5.8 099/232] dm: dont call report zones for more than the user requested

From: Johannes Thumshirn <johannes.thumshirn@....com>

commit a9cb9f4148ef6bb8fabbdaa85c42b2171fbd5a0d upstream.

Don't call report zones for more zones than the user actually requested,
otherwise this can lead to out-of-bounds accesses in the callback
functions.

Such a situation can happen if the target's ->report_zones() callback
function returns 0 because we've reached the end of the target and then
restart the report zones on the second target.

We're again calling into ->report_zones() and ultimately into the user
supplied callback function but when we're not subtracting the number of
zones already processed this may lead to out-of-bounds accesses in the
user callbacks.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@....com>
Reviewed-by: Damien Le Moal <damien.lemoal@....com>
Fixes: d41003513e61 ("block: rework zone reporting")
Cc: stable@...r.kernel.org # v5.5+
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/dm.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -504,7 +504,8 @@ static int dm_blk_report_zones(struct ge
 		}

 		args.tgt = tgt;
-		ret = tgt->type->report_zones(tgt, &args, nr_zones);
+		ret = tgt->type->report_zones(tgt, &args,
+					      nr_zones - args.zone_idx);
 		if (ret < 0)
 			goto out;
 	} while (args.zone_idx < nr_zones &&