linux-kernel - [PATCH AUTOSEL 6.9 02/15] md: Fix overflow in is_mddev

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Date: Sun, 26 May 2024 05:41:34 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Li Nan <linan122@...wei.com>,
	Yu Kuai <yukuai3@...wei.com>,
	Song Liu <song@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	axboe@...nel.dk,
	linux-raid@...r.kernel.org,
	linux-block@...r.kernel.org
Subject: [PATCH AUTOSEL 6.9 02/15] md: Fix overflow in is_mddev_idle

From: Li Nan <linan122@...wei.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@...wei.com>
Reviewed-by: Yu Kuai <yukuai3@...wei.com>
Link: https://lore.kernel.org/r/20240117031946.2324519-2-linan666@huaweicloud.com
Signed-off-by: Song Liu <song@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.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