[PATCH AUTOSEL 6.9 02/15] md: Fix overflow in is_mddev_idle

Sasha Levin
2024-05-26T09:41:56Z

From: Li Nan <linan122@huawei.com>

[ Upstream commit 3f9f231236ce7e48780d8a4f1f8cb9fae2df1e4e ]

UBSAN reports this problem:

UBSAN: Undefined behaviour in drivers/md/md.c:8175:15
signed integer overflow:
-2147483291 - 2072033152 cannot be represented in type 'int'
Call trace:
dump_backtrace+0x0/0x310
show_stack+0x28/0x38
dump_stack+0xec/0x15c
ubsan_epilogue+0x18/0x84
handle_overflow+0x14c/0x19c
__ubsan_handle_sub_overflow+0x34/0x44
is_mddev_idle+0x338/0x3d8
md_do_sync+0x1bb8/0x1cf8
md_thread+0x220/0x288
kthread+0x1d8/0x1e0
ret_from_fork+0x10/0x18

'curr_events' will overflow when stat accum or 'sync_io' is greater than
INT_MAX.

Fix it by changing sync_io, last_events and curr_events to 64bit.

Signed-off-by: Li Nan <linan122@huawei.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240117031946.2324519-2-linan666@huaweicloud.com
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/md/md.c | 7 ++++---
drivers/md/md.h | 4 ++--
include/linux/blkdev.h | 2 +-
3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index e575e74aabf5e..c88b50a4be82f 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -8576,14 +8576,15 @@ static int is_mddev_idle(struct mddev *mddev, int init)
{
struct md_rdev *rdev;
int idle;
- int curr_events;
+ long long curr_events;

idle = 1;
rcu_read_lock();
rdev_for_each_rcu(rdev, mddev) {
struct gendisk *disk = rdev->bdev->bd_disk;
- curr_events = (int)part_stat_read_accum(disk->part0, sectors) -
- atomic_read(&disk->sync_io);
+ curr_events =
+ (long long)part_stat_read_accum(disk->part0, sectors) -
+ atomic64_read(&disk->sync_io);
/* sync IO will cause sync_io to increase before the disk_stats
* as sync_io is counted when a request starts, and
* disk_stats is counted when it completes.
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 097d9dbd69b83..d0db98c0d33be 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -51,7 +51,7 @@ struct md_rdev {

sector_t sectors; /* Device size (in 512bytes sectors) */
struct mddev *mddev; /* RAID array if running */
- int last_events; /* IO event timestamp */
+ long long last_events; /* IO event timestamp */

/*
* If meta_bdev is non-NULL, it means that a separate device is
@@ -621,7 +621,7 @@ extern void mddev_unlock(struct mddev *mddev);

static inline void md_sync_acct(struct block_device *bdev, unsigned long nr_sectors)
{
- atomic_add(nr_sectors, &bdev->bd_disk->sync_io);
+ atomic64_add(nr_sectors, &bdev->bd_disk->sync_io);
}

static inline void md_sync_acct_bio(struct bio *bio, unsigned long nr_sectors)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 69e7da33ca49a..f10fb01a629fb 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -174,7 +174,7 @@ struct gendisk {
struct list_head slave_bdevs;
#endif
struct timer_rand_state *random;
- atomic_t sync_io; /* RAID */
+ atomic64_t sync_io; /* RAID */
struct disk_events *ev;

#ifdef CONFIG_BLK_DEV_ZONED
--
2.43.0