bcache: avoid nr_stripes overflow in bcache_device_init()

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>
Cc: stable@vger.kernel.org
Link: https://bugzilla.redhat.com/show_bug.cgi?id=1783075
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 4a77bfd..0f90616 100644 (file)
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -835,19 +835,19 @@ 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);