Commit 7a148126 authored by Coly Li's avatar Coly Li Committed by Jens Axboe
Browse files

bcache: fix overflow in offset_to_stripe() 



offset_to_stripe() returns the stripe number (in type unsigned int) from
an offset (in type uint64_t) by the following calculation,
	do_div(offset, d->stripe_size);
For large capacity backing device (e.g. 18TB) with small stripe size
(e.g. 4KB), the result is 4831838208 and exceeds UINT_MAX. The actual
returned value which caller receives is 536870912, due to the overflow.

Indeed in bcache_device_init(), bcache_device->nr_stripes is limited in
range [1, INT_MAX]. Therefore all valid stripe numbers in bcache are
in range [0, bcache_dev->nr_stripes - 1].

This patch adds a upper limition check in offset_to_stripe(): the max
valid stripe number should be less than bcache_device->nr_stripes. If
the calculated stripe number from do_div() is equal to or larger than
bcache_device->nr_stripe, -EINVAL will be returned. (Normally nr_stripes
is less than INT_MAX, exceeding upper limitation doesn't mean overflow,
therefore -EOVERFLOW is not used as error code.)

This patch also changes nr_stripes' type of struct bcache_device from
'unsigned int' to 'int', and return value type of offset_to_stripe()
from 'unsigned int' to 'int', to match their exact data ranges.

All locations where bcache_device->nr_stripes and offset_to_stripe() are
referenced also get updated for the above type change.

Reported-and-tested-by: default avatarKen Raeburn <raeburn@redhat.com>
Signed-off-by: default avatarColy Li <colyli@suse.de>
Cc: stable@vger.kernel.org
Link: https://bugzilla.redhat.com/show_bug.cgi?id=1783075


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 65f0f017

drivers/md/bcache/bcache.h

+1 −1
Original line number Diff line number Diff line
@@ -264,7 +264,7 @@ struct bcache_device { 
#define BCACHE_DEV_UNLINK_DONE		2

#define BCACHE_DEV_WB_RUNNING		3

#define BCACHE_DEV_RATE_DW_RUNNING	4

	unsigned int		nr_stripes;

	int			nr_stripes;

	unsigned int		stripe_size;

	atomic_t		*stripe_sectors_dirty;

	unsigned long		*full_dirty_stripes;

drivers/md/bcache/writeback.c

+9 −5
Original line number Diff line number Diff line
@@ -521,15 +521,19 @@ void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned int inode, 
				  uint64_t offset, int nr_sectors)

{

	struct bcache_device *d = c->devices[inode];

	unsigned int stripe_offset, stripe, sectors_dirty;

	unsigned int stripe_offset, sectors_dirty;

	int stripe;



	if (!d)

		return;



	stripe = offset_to_stripe(d, offset);

	if (stripe < 0)

		return;



	if (UUID_FLASH_ONLY(&c->uuids[inode]))

		atomic_long_add(nr_sectors, &c->flash_dev_dirty_sectors);



	stripe = offset_to_stripe(d, offset);

	stripe_offset = offset & (d->stripe_size - 1);



	while (nr_sectors) {
@@ -569,12 +573,12 @@ static bool dirty_pred(struct keybuf *buf, struct bkey *k) 
static void refill_full_stripes(struct cached_dev *dc)

{

	struct keybuf *buf = &dc->writeback_keys;

	unsigned int start_stripe, stripe, next_stripe;

	unsigned int start_stripe, next_stripe;

	int stripe;

	bool wrapped = false;



	stripe = offset_to_stripe(&dc->disk, KEY_OFFSET(&buf->last_scanned));



	if (stripe >= dc->disk.nr_stripes)

	if (stripe < 0)

		stripe = 0;



	start_stripe = stripe;

drivers/md/bcache/writeback.h

+17 −2
Original line number Diff line number Diff line
@@ -52,10 +52,22 @@ static inline uint64_t bcache_dev_sectors_dirty(struct bcache_device *d) 
	return ret;

}



static inline unsigned int offset_to_stripe(struct bcache_device *d,

static inline int offset_to_stripe(struct bcache_device *d,

					uint64_t offset)

{

	do_div(offset, d->stripe_size);



	/* d->nr_stripes is in range [1, INT_MAX] */

	if (unlikely(offset >= d->nr_stripes)) {

		pr_err("Invalid stripe %llu (>= nr_stripes %d).\n",

			offset, d->nr_stripes);

		return -EINVAL;

	}



	/*

	 * Here offset is definitly smaller than INT_MAX,

	 * return it as int will never overflow.

	 */

	return offset;

}
@@ -63,7 +75,10 @@ static inline bool bcache_dev_stripe_dirty(struct cached_dev *dc, 
					   uint64_t offset,

					   unsigned int nr_sectors)

{

	unsigned int stripe = offset_to_stripe(&dc->disk, offset);

	int stripe = offset_to_stripe(&dc->disk, offset);



	if (stripe < 0)

		return false;



	while (1) {

		if (atomic_read(dc->disk.stripe_sectors_dirty + stripe))