在 2025/9/5 18:24, Han Guangjiang 写道:
From: Han Guangjiang<hanguangjiang@xxxxxxxxxxx>
On repeated cold boots we occasionally hit a NULL pointer crash in
blk_should_throtl() when throttling is consulted before the throttle
policy is fully enabled for the queue. Checking only q->td != NULL is
insufficient during early initialization, so blkg_to_pd() for the
throttle policy can still return NULL and blkg_to_tg() becomes NULL,
which later gets dereferenced.
Unable to handle kernel NULL pointer dereference
at virtual address 0000000000000156
...
pc : submit_bio_noacct+0x14c/0x4c8
lr : submit_bio_noacct+0x48/0x4c8
sp : ffff800087f0b690
x29: ffff800087f0b690 x28: 0000000000005f90 x27: ffff00068af393c0
x26: 0000000000080000 x25: 000000000002fbc0 x24: ffff000684ddcc70
x23: 0000000000000000 x22: 0000000000000000 x21: 0000000000000000
x20: 0000000000080000 x19: ffff000684ddcd08 x18: ffffffffffffffff
x17: 0000000000000000 x16: ffff80008132a550 x15: 0000ffff98020fff
x14: 0000000000000000 x13: 1fffe000d11d7021 x12: ffff000688eb810c
x11: ffff00077ec4bb80 x10: ffff000688dcb720 x9 : ffff80008068ef60
x8 : 00000a6fb8a86e85 x7 : 000000000000111e x6 : 0000000000000002
x5 : 0000000000000246 x4 : 0000000000015cff x3 : 0000000000394500
x2 : ffff000682e35e40 x1 : 0000000000364940 x0 : 000000000000001a
Call trace:
submit_bio_noacct+0x14c/0x4c8
verity_map+0x178/0x2c8
__map_bio+0x228/0x250
dm_submit_bio+0x1c4/0x678
__submit_bio+0x170/0x230
submit_bio_noacct_nocheck+0x16c/0x388
submit_bio_noacct+0x16c/0x4c8
submit_bio+0xb4/0x210
f2fs_submit_read_bio+0x4c/0xf0
f2fs_mpage_readpages+0x3b0/0x5f0
f2fs_readahead+0x90/0xe8
Tighten blk_throtl_activated() to also require that the throttle policy
bit is set on the queue:
return q->td != NULL &&
test_bit(blkcg_policy_throtl.plid, q->blkcg_pols);
This prevents blk_should_throtl() from accessing throttle group state
until policy data has been attached to blkgs.
Fixes: a3166c51702b ("blk-throttle: delay initialization until configuration")
Co-developed-by: Liang Jie<liangjie@xxxxxxxxxxx>
Signed-off-by: Liang Jie<liangjie@xxxxxxxxxxx>
Signed-off-by: Han Guangjiang<hanguangjiang@xxxxxxxxxxx>
---
v2:
- remove the comment about freeze queue in blk_should_throtl()
- Retitle: "blk-throttle: fix access race during throttle policy activation"
v3:
- move blkcg_policy_enabled() to blk-cgroup.h
- use blkcg_policy_enabled() instead in blk_throtl_activated()
- remove the comment about freeze queue in blk_throtl_init()
- add some comments to decribe the throttle init synchronization
- Link to v2:https://lore.kernel.org/lkml/tencent_2B678DA920124B08854638A6BE68746CCC05@xxxxxx/
---
block/blk-cgroup.c | 6 ------
block/blk-cgroup.h | 6 ++++++
block/blk-throttle.c | 6 +-----
block/blk-throttle.h | 18 +++++++++++-------
4 files changed, 18 insertions(+), 18 deletions(-)
LGTM
Reviewed-by: Yu Kuai <yukuai3@xxxxxxxxxx>
