kernel/linux.git/block, branch v6.1.176

blk-cgroup: Fix NULL deref caused by blkg_policy_data being installed before init

2026-06-19T11:37:30+00:00

commit ec14a87ee1999b19d8b7ed0fa95fea80644624ae upstream. blk-iocost sometimes causes the following crash: BUG: kernel NULL pointer dereference, address: 00000000000000e0 ... RIP: 0010:_raw_spin_lock+0x17/0x30 Code: be 01 02 00 00 e8 79 38 39 ff 31 d2 89 d0 5d c3 0f 1f 00 0f 1f 44 00 00 55 48 89 e5 65 ff 05 48 d0 34 7e b9 01 00 00 00 31 c0 0f b1 0f 75 02 5d c3 89 c6 e8 ea 04 00 00 5d c3 0f 1f 84 00 00 RSP: 0018:ffffc900023b3d40 EFLAGS: 00010046 RAX: 0000000000000000 RBX: 00000000000000e0 RCX: 0000000000000001 RDX: ffffc900023b3d20 RSI: ffffc900023b3cf0 RDI: 00000000000000e0 RBP: ffffc900023b3d40 R08: ffffc900023b3c10 R09: 0000000000000003 R10: 0000000000000064 R11: 000000000000000a R12: ffff888102337000 R13: fffffffffffffff2 R14: ffff88810af408c8 R15: ffff8881070c3600 FS: 00007faaaf364fc0(0000) GS:ffff88842fdc0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000000000e0 CR3: 00000001097b1000 CR4: 0000000000350ea0 Call Trace: ioc_weight_write+0x13d/0x410 cgroup_file_write+0x7a/0x130 kernfs_fop_write_iter+0xf5/0x170 vfs_write+0x298/0x370 ksys_write+0x5f/0xb0 __x64_sys_write+0x1b/0x20 do_syscall_64+0x3d/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0 This happens because iocg->ioc is NULL. The field is initialized by ioc_pd_init() and never cleared. The NULL deref is caused by blkcg_activate_policy() installing blkg_policy_data before initializing it. blkcg_activate_policy() was doing the following: 1. Allocate pd's for all existing blkg's and install them in blkg->pd[]. 2. Initialize all pd's. 3. Online all pd's. blkcg_activate_policy() only grabs the queue_lock and may release and re-acquire the lock as allocation may need to sleep. ioc_weight_write() grabs blkcg->lock and iterates all its blkg's. The two can race and if ioc_weight_write() runs during #1 or between #1 and #2, it can encounter a pd which is not initialized yet, leading to crash. The crash can be reproduced with the following script: #!/bin/bash echo +io > /sys/fs/cgroup/cgroup.subtree_control systemd-run --unit touch-sda --scope dd if=/dev/sda of=/dev/null bs=1M count=1 iflag=direct echo 100 > /sys/fs/cgroup/system.slice/io.weight bash -c "echo '8:0 enable=1' > /sys/fs/cgroup/io.cost.qos" & sleep .2 echo 100 > /sys/fs/cgroup/system.slice/io.weight with the following patch applied: > diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c > index fc49be622e05..38d671d5e10c 100644 > --- a/block/blk-cgroup.c > +++ b/block/blk-cgroup.c > @@ -1553,6 +1553,12 @@ int blkcg_activate_policy(struct gendisk *disk, const struct blkcg_policy *pol) > pd->online = false; > } > > + if (system_state == SYSTEM_RUNNING) { > + spin_unlock_irq(&q->queue_lock); > + ssleep(1); > + spin_lock_irq(&q->queue_lock); > + } > + > /* all allocated, init in the same order */ > if (pol->pd_init_fn) > list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) I don't see a reason why all pd's should be allocated, initialized and onlined together. The only ordering requirement is that parent blkgs to be initialized and onlined before children, which is guaranteed from the walking order. Let's fix the bug by allocating, initializing and onlining pd for each blkg and holding blkcg->lock over initialization and onlining. This ensures that an installed blkg is always fully initialized and onlined removing the the race window. Signed-off-by: Tejun Heo Reported-by: Breno Leitao Fixes: 9d179b865449 ("blkcg: Fix multiple bugs in blkcg_activate_policy()") Link: https://lore.kernel.org/r/ZN0p5_W-Q9mAHBVY@slm.duckdns.org Signed-off-by: Jens Axboe Signed-off-by: Robert Garcia Signed-off-by: Greg Kroah-Hartman

blk-cgroup: wait for blkcg cleanup before initializing new disk

2026-06-01T15:39:04+00:00

[ Upstream commit 3dbaacf6ab68f81e3375fe769a2ecdbd3ce386fd ] When a queue is shared across disk rebind (e.g., SCSI unbind/bind), the previous disk's blkcg state is cleaned up asynchronously via disk_release() -> blkcg_exit_disk(). If the new disk's blkcg_init_disk() runs before that cleanup finishes, we may overwrite q->root_blkg while the old one is still alive, and radix_tree_insert() in blkg_create() fails with -EEXIST because the old blkg entries still occupy the same queue id slot in blkcg->blkg_tree. This causes the sd probe to fail with -ENOMEM. Fix it by waiting in blkcg_init_disk() for root_blkg to become NULL, which indicates the previous disk's blkcg cleanup has completed. Fixes: 1059699f87eb ("block: move blkcg initialization/destroy into disk allocation/release handler") Cc: Yi Zhang Signed-off-by: Ming Lei Reviewed-by: Christoph Hellwig Link: https://patch.msgid.link/20260311032837.2368714-1-ming.lei@redhat.com Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

blk-mq: fix NULL dereference on q->elevator in blk_mq_elv_switch_none

2026-06-01T15:38:44+00:00

[ Upstream commit 245165658e1c9f95c0fecfe02b9b1ebd30a1198a ] After grabbing q->sysfs_lock, q->elevator may become NULL because of elevator switch. Fix the NULL dereference on q->elevator by checking it with lock. Reported-by: Guangwu Zhang Signed-off-by: Ming Lei Link: https://lore.kernel.org/r/20230616132354.415109-1-ming.lei@redhat.com Signed-off-by: Jens Axboe Signed-off-by: Leon Chen Signed-off-by: Sasha Levin

block: Fix the blk_mq_destroy_queue() documentation

2026-04-11T12:16:38+00:00

commit 81ea42b9c3d61ea34d82d900ed93f4b4851f13b0 upstream. Commit 2b3f056f72e5 moved a blk_put_queue() call from blk_mq_destroy_queue() into its callers. Reflect this change in the documentation block above blk_mq_destroy_queue(). Cc: Christoph Hellwig Cc: Sagi Grimberg Cc: Chaitanya Kulkarni Cc: Keith Busch Fixes: 2b3f056f72e5 ("blk-mq: move the call to blk_put_queue out of blk_mq_destroy_queue") Signed-off-by: Bart Van Assche Reviewed-by: Christoph Hellwig Link: https://lore.kernel.org/r/20230130211233.831613-1-bvanassche@acm.org Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

block: fix resource leak in blk_register_queue() error path

2026-04-11T12:16:34+00:00

[ Upstream commit 40f2eb9b531475dd01b683fdaf61ca3cfd03a51e ] When registering a queue fails after blk_mq_sysfs_register() is successful but the function later encounters an error, we need to clean up the blk_mq_sysfs resources. Add the missing blk_mq_sysfs_unregister() call in the error path to properly clean up these resources and prevent a memory leak. Fixes: 320ae51feed5 ("blk-mq: new multi-queue block IO queueing mechanism") Signed-off-by: Zheng Qixing Reviewed-by: Christoph Hellwig Reviewed-by: Yu Kuai Link: https://lore.kernel.org/r/20250412092554.475218-1-zhengqixing@huaweicloud.com Signed-off-by: Jens Axboe [ Minor context change fixed. ] Signed-off-by: Robert Garcia Signed-off-by: Greg Kroah-Hartman

blk-mq: move the call to blk_put_queue out of blk_mq_destroy_queue

2026-04-11T12:16:33+00:00

[ Upstream commit 2b3f056f72e56fa07df69b4705e0b46a6c08e77c ] The fact that blk_mq_destroy_queue also drops a queue reference leads to various places having to grab an extra reference. Move the call to blk_put_queue into the callers to allow removing the extra references. Signed-off-by: Christoph Hellwig Reviewed-by: Sagi Grimberg Reviewed-by: Chaitanya Kulkarni Reviewed-by: Keith Busch Link: https://lore.kernel.org/r/20221018135720.670094-2-hch@lst.de [axboe: fix fabrics_q vs admin_q conflict in nvme core.c] Signed-off-by: Jens Axboe Stable-dep-of: 03b3bcd319b3 ("nvme: fix admin request_queue lifetime") Signed-off-by: Maximilian Heyne Tested-by: Fedor Pchelkin Signed-off-by: Sasha Levin

blk-mq-debugfs: add missing debugfs_mutex in blk_mq_debugfs_register_hctxs()

2026-03-04T12:20:15+00:00

[ Upstream commit 9d20fd6ce1ba9733cd5ac96fcab32faa9fc404dd ] In blk_mq_update_nr_hw_queues(), debugfs_mutex is not held while creating debugfs entries for hctxs. Hence add debugfs_mutex there, it's safe because queue is not frozen. Signed-off-by: Yu Kuai Reviewed-by: Nilay Shroff Reviewed-by: Ming Lei Reviewed-by: Hannes Reinecke Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

block,bfq: fix aux stat accumulation destination

2026-02-11T12:37:21+00:00

[ Upstream commit 04bdb1a04d8a2a89df504c1e34250cd3c6e31a1c ] Route bfqg_stats_add_aux() time accumulation into the destination stats object instead of the source, aligning with other stat fields. Reviewed-by: Yu Kuai Signed-off-by: shechenglong Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

blk-cgroup: Reinit blkg_iostat_set after clearing in blkcg_reset_stats()

2026-02-06T15:44:23+00:00

[ Upstream commit 3d2af77e31ade05ff7ccc3658c3635ec1bea0979 ] When blkg_alloc() is called to allocate a blkcg_gq structure with the associated blkg_iostat_set's, there are 2 fields within blkg_iostat_set that requires proper initialization - blkg & sync. The former field was introduced by commit 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()") while the later one was introduced by commit f73316482977 ("blk-cgroup: reimplement basic IO stats using cgroup rstat"). Unfortunately those fields in the blkg_iostat_set's are not properly re-initialized when they are cleared in v1's blkcg_reset_stats(). This can lead to a kernel panic due to NULL pointer access of the blkg pointer. The missing initialization of sync is less problematic and can be a problem in a debug kernel due to missing lockdep initialization. Fix these problems by re-initializing them after memory clearing. Fixes: 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()") Fixes: f73316482977 ("blk-cgroup: reimplement basic IO stats using cgroup rstat") Signed-off-by: Waiman Long Reviewed-by: Ming Lei Acked-by: Tejun Heo Link: https://lore.kernel.org/r/20230606180724.2455066-1-longman@redhat.com Signed-off-by: Jens Axboe [ Remove this line: bis -> blkg = blkg for blkg was introduced by commit 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()") since v6.2. ] Signed-off-by: Alva Lan Signed-off-by: Greg Kroah-Hartman

blk-mq: setup queue ->tag_set before initializing hctx

2026-01-11T14:19:26+00:00

commit c25c0c9035bb8b28c844dfddeda7b8bdbcfcae95 upstream. Commit 7b815817aa58 ("blk-mq: add helper for checking if one CPU is mapped to specified hctx") needs to check queue mapping via tag set in hctx's cpuhp handler. However, q->tag_set may not be setup yet when the cpuhp handler is enabled, then kernel oops is triggered. Fix the issue by setup queue tag_set before initializing hctx. Cc: stable@vger.kernel.org Reported-and-tested-by: Rick Koch Closes: https://lore.kernel.org/linux-block/CANa58eeNDozLaBHKPLxSAhEy__FPfJT_F71W=sEQw49UCrC9PQ@mail.gmail.com Fixes: 7b815817aa58 ("blk-mq: add helper for checking if one CPU is mapped to specified hctx") Signed-off-by: Ming Lei Reviewed-by: Christoph Hellwig Reviewed-by: John Garry Link: https://lore.kernel.org/r/20241014005115.2699642-1-ming.lei@redhat.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman