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

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Hi,

在 2024/05/26 17:41, Sasha Levin 写道:
From: Li Nan <linan122@xxxxxxxxxx>

[ 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@xxxxxxxxxx>
Reviewed-by: Yu Kuai <yukuai3@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240117031946.2324519-2-linan666@xxxxxxxxxxxxxxx
Signed-off-by: Song Liu <song@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

Hi, please notice that this patch doesn't fix real issue expect for
the ubsan warning, and this patch is reverted:
---
  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





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