[PATCH 5.4 016/107] bcache: avoid nr_stripes overflow in bcache_device_init()

Greg Kroah-Hartman
2020-08-24T09:41:56Z

From: Coly Li <colyli@suse.de>

[ Upstream commit 65f0f017e7be8c70330372df23bcb2a407ecf02d ]

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>
Signed-off-by: Sasha Levin <sashal@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 25ad64a3919f6..2cbfcd99b7ee7 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -816,19 +816,19 @@ 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?)",
- (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);
--
2.25.1