linux-kernel - [PATCH 3.16 45/83] dm table: fix invalid memory accesses with too high sector number

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Message-ID: <lsq.1574264230.403316458@decadent.org.uk>
Date:   Wed, 20 Nov 2019 15:37:55 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Zhang Tao" <kontais@...o.com>,
        "Mike Snitzer" <snitzer@...hat.com>,
        "Mikulas Patocka" <mpatocka@...hat.com>
Subject: [PATCH 3.16 45/83] dm table: fix invalid memory accesses with too
 high sector number

3.16.78-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Mikulas Patocka <mpatocka@...hat.com>

commit 1cfd5d3399e87167b7f9157ef99daa0e959f395d upstream.

If the sector number is too high, dm_table_find_target() should return a
pointer to a zeroed dm_target structure (the caller should test it with
dm_target_is_valid).

However, for some table sizes, the code in dm_table_find_target() that
performs btree lookup will access out of bound memory structures.

Fix this bug by testing the sector number at the beginning of
dm_table_find_target(). Also, add an "inline" keyword to the function
dm_table_get_size() because this is a hot path.

Fixes: 512875bd9661 ("dm: table detect io beyond device")
Reported-by: Zhang Tao <kontais@...o.com>
Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/md/dm-table.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1158,7 +1158,7 @@ void dm_table_event(struct dm_table *t)
 }
 EXPORT_SYMBOL(dm_table_event);
 
-sector_t dm_table_get_size(struct dm_table *t)
+inline sector_t dm_table_get_size(struct dm_table *t)
 {
 	return t->num_targets ? (t->highs[t->num_targets - 1] + 1) : 0;
 }
@@ -1183,6 +1183,9 @@ struct dm_target *dm_table_find_target(s
 	unsigned int l, n = 0, k = 0;
 	sector_t *node;
 
+	if (unlikely(sector >= dm_table_get_size(t)))
+		return &t->targets[t->num_targets];
+
 	for (l = 0; l < t->depth; l++) {
 		n = get_child(n, k);
 		node = get_node(t, l, n);