md: Fix overflow in is_mddev_idle

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>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index fd574b015d786b59d12f072832c6f4be8267a408..f28e41f9ac4aa2461c2673a211ab2ff0fa3ae069 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -8577,14 +8577,15 @@ 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 097d9dbd69b8363df9ba69ed0d89cab05577151b..d0db98c0d33bea08a0a29b8225a2cca3db712fe7 100644 (file)
--- 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 c3e8f7cf96be9e1c10169d2e7afe31696082eb8f..d0fa4f1c29a2bde286a339ebeabdbab21daf2b75 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -172,7 +172,7 @@ 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