Linux Kernel up to 7.2.9/7.3-rc5 blk-cgroup blkg_tryget_closest deadlock

Summaryinfo

A vulnerability was found in Linux Kernel up to 7.2.9/7.3-rc5 and classified as critical. This affects the function blkg_tryget_closest of the component blk-cgroup. Executing a manipulation can lead to deadlock. This vulnerability is tracked as CVE-2026-98832. The attack can be launched remotely. No exploit exists. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 7.2.9/7.3-rc5 and classified as critical. This vulnerability affects the function blkg_tryget_closest of the component blk-cgroup. The manipulation with an unknown input leads to a deadlock vulnerability. The CWE definition for the vulnerability is CWE-833. The product contains multiple threads or executable segments that are waiting for each other to release a necessary lock, resulting in deadlock. As an impact it is known to affect availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: blk-cgroup: save IRQ state in blkg_tryget_closest() bio_set_dev() associates the bio with a blkg through bio_associate_blkg(). If the blkg lookup misses, blkg_tryget_closest() takes q->queue_lock with spin_lock_irq() and releases it with spin_unlock_irq(), which unconditionally enables local interrupts. Callers may call bio_set_dev() with interrupts already disabled, e.g. dm-thin's pool_map() does so while holding pool->lock taken with spin_lock_irq(). The nested spin_unlock_irq() then enables interrupts while pool->lock is still held, so an I/O completion softirq can run on the same CPU, re-acquire pool->lock (thin_endio(), or overwrite_endio() -> complete_mapping_preparation()) and deadlock. lockdep reports this as inconsistent SOFTIRQ-ON-W to IN-SOFTIRQ-W usage. Commit 3a762de55b4e ("block: save irq state in blkg_lookup_create()") fixed the same problem while the lock lived in blkg_lookup_create(), but commit 9327a865e395 ("blk-cgroup: don't nest queue_lock under rcu in blkg_lookup_create()") moved the locking into blkg_tryget_closest() and reverted it to spin_lock_irq(). Save and restore the caller's IRQ state instead.

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2026-98832 since 09/25/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 10/18/2026). The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading to version 7.2.10 or 7.3-rc6 eliminates this vulnerability. Applying the patch 9fcf4317384ce6758c3127a6e8914c54cbb9c8cc/327c428ba79b13e4cc5253333a9d5c0aa5579bdf is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.2.5
• 7.2.6
• 7.2.7
• 7.2.8
• 7.2.9
• 7.3-rc1
• 7.3-rc2
• 7.3-rc3
• 7.3-rc4
• 7.3-rc5

License

• open-source

Website

• Vendor: https://www.kernel.org/

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