[PATCH 07/25] bcache: avoid nr_stripes overflow in bcache_device_init() - Linux-stable-mirror

25 Jul 2020

For some block devices which large capacity (e.g. 8TB) but small io_opt
size (e.g. 8 sectors), in bcache_device_init() the stripes number calcu-
lated by,
    DIV_ROUND_UP_ULL(sectors, d->stripe_size);
might be overflow to the unsigned int bcache_device->nr_stripes.
This patch uses the uint64_t variable to store DIV_ROUND_UP_ULL()
and after the value is checked to be available in unsigned int range,
sets it to bache_device->nr_stripes. Then the overflow is avoided.
Reported-and-tested-by: Ken Raeburn raeburn@redhat.com
Signed-off-by: Coly Li colyli@suse.de
Link: https://bugzilla.redhat.com/show_bug.cgi?id=1783075
Cc: stable@vger.kernel.org
---
 drivers/md/bcache/super.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 6db698b1739a..05ad1cd9f329 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -826,19 +826,19 @@ static int bcache_device_init(struct bcache_device *d, unsigned int block_size,
    struct request_queue *q;
    const size_t max_stripes = min_t(size_t, INT_MAX,
    				 SIZE_MAX / sizeof(atomic_t));
-	size_t n;
+	uint64_t n;
    int idx;
if (!d->stripe_size)
    	d->stripe_size = 1 << 31;
-	d->nr_stripes = DIV_ROUND_UP_ULL(sectors, d->stripe_size);
-
-	if (!d->nr_stripes || d->nr_stripes > max_stripes) {
-		pr_err("nr_stripes too large or invalid: %u (start sector beyond end of disk?)\n",
-			(unsigned int)d->nr_stripes);
+	n = DIV_ROUND_UP_ULL(sectors, d->stripe_size);
+	if (!n || n > max_stripes) {
+		pr_err("nr_stripes too large or invalid: %llu (start sector beyond end of disk?)\n",
+			n);
    	return -ENOMEM;
    }
+	d->nr_stripes = n;
n = d->nr_stripes * sizeof(atomic_t);
    d->stripe_sectors_dirty = kvzalloc(n, GFP_KERNEL);
-- 
2.26.2


    