[PATCH][next] dm btree: Fix potential read of array with negative index i

From: Colin King <colin.king@canonical.com>
To: Alasdair Kergon <agk@redhat.com>,
	Mike Snitzer <snitzer@redhat.com>,
	dm-devel@redhat.com, Joe Thornber <ejt@redhat.com>
Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH][next] dm btree: Fix potential read of array with negative index i
Date: Fri, 21 May 2021 11:52:36 +0100	[thread overview]
Message-ID: <20210521105236.43860-1-colin.king@canonical.com> (raw)

From: Colin Ian King <colin.king@canonical.com>

The call to lower_bound can return -1 if the key is not found
with the bsearch, leading to a negative index access into
array node->keys[]. Ensure this cannot occur by checking for
a negative index before reading from the array.

Addresses-Coverity: ("Negative array index read")
Fixes: d69e2e7e28bd ("dm btree: improve btree residency")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/md/persistent-data/dm-btree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/persistent-data/dm-btree.c b/drivers/md/persistent-data/dm-btree.c
index b8d21b6e2953..266deaea5eea 100644
--- a/drivers/md/persistent-data/dm-btree.c
+++ b/drivers/md/persistent-data/dm-btree.c
@@ -1048,7 +1048,7 @@ static bool contains_key(struct btree_node *node, uint64_t key)
 {
 	int i = lower_bound(node, key);
 
-	if (le64_to_cpu(node->keys[i]) == key)
+	if (i >= 0 && le64_to_cpu(node->keys[i]) == key)
 		return true;
 
 	return false;
-- 
2.31.1

