Commit efbec3f1 authored by Yu Kuai's avatar Yu Kuai Committed by Li Nan
Browse files

md: fix resync softlockup when bitmap size is less than array size 

mainline inclusion
from mainline-v6.10-rc1
commit f0e729af2eb6bee9eb58c4df1087f14ebaefe26b
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IA6SH1
CVE: CVE-2024-38598

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=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 301867b1 ("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: 301867b1 ("md/raid10: check slab-out-of-bounds in md_bitmap_get_counter")
Reported-and-tested-by: default avatarNigel Croxon <ncroxon@redhat.com>
Closes: https://lore.kernel.org/all/71ba5272-ab07-43ba-8232-d2da642acb4e@redhat.com/


Signed-off-by: default avatarYu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240422065824.2516-1-yukuai1@huaweicloud.com


Signed-off-by: default avatarSong Liu <song@kernel.org>
Signed-off-by: default avatarLi Nan <linan122@huawei.com>
parent 6445deff

drivers/md/md-bitmap.c

+3 −3
Original line number Diff line number Diff line
@@ -1398,7 +1398,7 @@ __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) {
@@ -1407,6 +1407,7 @@ __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);
@@ -1415,8 +1416,7 @@ __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)