From: Yu Kuai yukuai3@huawei.com

mainline inclusion from mainline-v6.10-rc1 commit a2db328b0839312c169eb42746ec46fc1ab53ed2 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IA7D6H CVE: CVE-2024-36478

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

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Writing 'power' and 'submit_queues' concurrently will trigger kernel panic:

Test script:

modprobe null_blk nr_devices=0 mkdir -p /sys/kernel/config/nullb/nullb0 while true; do echo 1 > submit_queues; echo 4 > submit_queues; done & while true; do echo 1 > power; echo 0 > power; done

Test result:

BUG: kernel NULL pointer dereference, address: 0000000000000148 Oops: 0000 [#1] PREEMPT SMP RIP: 0010:__lock_acquire+0x41d/0x28f0 Call Trace: <TASK> lock_acquire+0x121/0x450 down_write+0x5f/0x1d0 simple_recursive_removal+0x12f/0x5c0 blk_mq_debugfs_unregister_hctxs+0x7c/0x100 blk_mq_update_nr_hw_queues+0x4a3/0x720 nullb_update_nr_hw_queues+0x71/0xf0 [null_blk] nullb_device_submit_queues_store+0x79/0xf0 [null_blk] configfs_write_iter+0x119/0x1e0 vfs_write+0x326/0x730 ksys_write+0x74/0x150

This is because del_gendisk() can concurrent with blk_mq_update_nr_hw_queues():

nullb_device_power_store nullb_apply_submit_queues null_del_dev del_gendisk nullb_update_nr_hw_queues if (!dev->nullb) // still set while gendisk is deleted return 0 blk_mq_update_nr_hw_queues dev->nullb = NULL

Fix this problem by resuing the global mutex to protect nullb_device_power_store() and nullb_update_nr_hw_queues() from configfs.

Fixes: 45919fbfe1c4 ("null_blk: Enable modifying 'submit_queues' after an instance has been configured") Reported-and-tested-by: Yi Zhang yi.zhang@redhat.com Closes: https://lore.kernel.org/all/CAHj4cs9LgsHLnjg8z06LQ3Pr5cax-+Ps+xT7AP7TPnEjStu... Signed-off-by: Yu Kuai yukuai3@huawei.com Reviewed-by: Zhu Yanjun yanjun.zhu@linux.dev Link: https://lore.kernel.org/r/20240523153934.1937851-1-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe axboe@kernel.dk Conflicts: drivers/block/null_blk/main.c [ A lot of conflict, this patch just expand the protection range of mutex, ignore conflict. ] Signed-off-by: Li Nan linan122@huawei.com --- drivers/block/null_blk/main.c | 43 +++++++++++++++++++++-------------- 1 file changed, 26 insertions(+), 17 deletions(-)

diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c index 35b390a785dd..91c8412442d0 100644 --- a/drivers/block/null_blk/main.c +++ b/drivers/block/null_blk/main.c @@ -323,11 +323,9 @@ CONFIGFS_ATTR(nullb_device_, NAME); static int nullb_apply_submit_queues(struct nullb_device *dev, unsigned int submit_queues) { - struct nullb *nullb = dev->nullb; + struct nullb *nullb; struct blk_mq_tag_set *set; - - if (!nullb) - return 0; + int ret = 0;

/* * Make sure that null_init_hctx() does not access nullb->queues[] past @@ -335,9 +333,20 @@ static int nullb_apply_submit_queues(struct nullb_device *dev, */ if (submit_queues > nr_cpu_ids) return -EINVAL; + + mutex_lock(&lock); + + nullb = dev->nullb; + if (!nullb) + goto out; + set = nullb->tag_set; blk_mq_update_nr_hw_queues(set, submit_queues); - return set->nr_hw_queues == submit_queues ? 0 : -ENOMEM; + ret = set->nr_hw_queues == submit_queues ? 0 : -ENOMEM; + +out: + mutex_unlock(&lock); + return ret; }

NULLB_DEVICE_ATTR(size, ulong, NULL); @@ -378,27 +387,31 @@ static ssize_t nullb_device_power_store(struct config_item *item, if (ret < 0) return ret;

+ ret = count; + mutex_lock(&lock); if (!dev->power && newp) { if (test_and_set_bit(NULLB_DEV_FL_UP, &dev->flags)) - return count; + goto out; + if (null_add_dev(dev)) { clear_bit(NULLB_DEV_FL_UP, &dev->flags); - return -ENOMEM; + ret = -ENOMEM; + goto out; }

set_bit(NULLB_DEV_FL_CONFIGURED, &dev->flags); dev->power = newp; } else if (dev->power && !newp) { if (test_and_clear_bit(NULLB_DEV_FL_UP, &dev->flags)) { - mutex_lock(&lock); dev->power = newp; null_del_dev(dev->nullb); - mutex_unlock(&lock); } clear_bit(NULLB_DEV_FL_CONFIGURED, &dev->flags); }

- return count; +out: + mutex_unlock(&lock); + return ret; }

CONFIGFS_ATTR(nullb_device_, power); @@ -1880,15 +1893,11 @@ static int null_add_dev(struct nullb_device *dev) blk_queue_flag_set(QUEUE_FLAG_NONROT, nullb->q); blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, nullb->q);

- mutex_lock(&lock); rv = ida_simple_get(&nullb_indexes, 0, 0, GFP_KERNEL); - if (rv < 0) { - mutex_unlock(&lock); + if (rv < 0) goto out_cleanup_zone; - } nullb->index = rv; dev->index = rv; - mutex_unlock(&lock);

blk_queue_logical_block_size(nullb->q, dev->blocksize); blk_queue_physical_block_size(nullb->q, dev->blocksize); @@ -1901,9 +1910,7 @@ static int null_add_dev(struct nullb_device *dev) if (rv) goto out_ida_free;

- mutex_lock(&lock); list_add_tail(&nullb->list, &nullb_list); - mutex_unlock(&lock);

return 0;

@@ -1985,7 +1992,9 @@ static int __init null_init(void) ret = -ENOMEM; goto err_dev; } + mutex_lock(&lock); ret = null_add_dev(dev); + mutex_unlock(&lock); if (ret) { null_free_dev(dev); goto err_dev;