[PATCH 6.1 086/473] md: fix resync softlockup when bitmap size is less than array size

Greg Kroah-Hartman
2024-06-06T14:13:28Z

From: Yu Kuai <yukuai3@huawei.com>

[ Upstream commit f0e729af2eb6bee9eb58c4df1087f14ebaefe26b ]

Is is reported that for dm-raid10, lvextend + lvchange --syncaction will
trigger following softlockup:

kernel:watchdog: BUG: soft lockup - CPU#3 stuck for 26s! [mdX_resync:6976]
CPU: 7 PID: 3588 Comm: mdX_resync Kdump: loaded Not tainted 6.9.0-rc4-next-20240419 #1
RIP: 0010:_raw_spin_unlock_irq+0x13/0x30
Call Trace:
<TASK>
md_bitmap_start_sync+0x6b/0xf0
raid10_sync_request+0x25c/0x1b40 [raid10]
md_do_sync+0x64b/0x1020
md_thread+0xa7/0x170
kthread+0xcf/0x100
ret_from_fork+0x30/0x50
ret_from_fork_asm+0x1a/0x30

And the detailed process is as follows:

md_do_sync
j = mddev->resync_min
while (j < max_sectors)
sectors = raid10_sync_request(mddev, j, &skipped)
if (!md_bitmap_start_sync(..., &sync_blocks))
// md_bitmap_start_sync set sync_blocks to 0
return sync_blocks + sectors_skippe;
// sectors = 0;
j += sectors;
// j never change

Root cause is that commit 301867b1c168 ("md/raid10: check
slab-out-of-bounds in md_bitmap_get_counter") return early from
md_bitmap_get_counter(), without setting returned blocks.

Fix this problem by always set returned blocks from
md_bitmap_get_counter"(), as it used to be.

Noted that this patch just fix the softlockup problem in kernel, the
case that bitmap size doesn't match array size still need to be fixed.

Fixes: 301867b1c168 ("md/raid10: check slab-out-of-bounds in md_bitmap_get_counter")
Reported-and-tested-by: Nigel Croxon <ncroxon@redhat.com>
Closes: https://lore.kernel.org/all/71ba5272-ab07-43ba-8232-d2da642acb4e@redhat.com/
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240422065824.2516-1-yukuai1@huaweicloud.com
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/md/md-bitmap.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index 5200bba63708e..9d8ac04c23462 100644
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c
@@ -1352,7 +1352,7 @@ __acquires(bitmap->lock)
sector_t chunk = offset >> bitmap->chunkshift;
unsigned long page = chunk >> PAGE_COUNTER_SHIFT;
unsigned long pageoff = (chunk & PAGE_COUNTER_MASK) << COUNTER_BYTE_SHIFT;
- sector_t csize;
+ sector_t csize = ((sector_t)1) << bitmap->chunkshift;
int err;

if (page >= bitmap->pages) {
@@ -1361,6 +1361,7 @@ __acquires(bitmap->lock)
* End-of-device while looking for a whole page or
* user set a huge number to sysfs bitmap_set_bits.
*/
+ *blocks = csize - (offset & (csize - 1));
return NULL;
}
err = md_bitmap_checkpage(bitmap, page, create, 0);
@@ -1369,8 +1370,7 @@ __acquires(bitmap->lock)
bitmap->bp[page].map == NULL)
csize = ((sector_t)1) << (bitmap->chunkshift +
PAGE_COUNTER_SHIFT);
- else
- csize = ((sector_t)1) << bitmap->chunkshift;
+
*blocks = csize - (offset & (csize - 1));

if (err < 0)
--
2.43.0