CVE-2024-26899

In the Linux kernel, the following vulnerability has been resolved:

block: fix deadlock between bd_link_disk_holder and partition scan

open_mutex of gendisk is used to protect open/close block devices. But in bd_link_disk_holder(), it is used to protect the creation of symlink between holding disk and slave bdev, which introduces some issues.

When bd_link_disk_holder() is called, the driver is usually in the process of initialization/modification and may suspend submitting io. At this time, any io hold open_mutex, such as scanning partitions, can cause deadlocks. For example, in raid:

T1 T2 bdev_open_by_dev lock open_mutex [1] … efi_partition … md_submit_bio md_ioctl mddev_syspend -> suspend all io md_add_new_disk bind_rdev_to_array bd_link_disk_holder try lock open_mutex [2] md_handle_request -> wait mddev_resume

T1 scan partition, T2 add a new device to raid. T1 waits for T2 to resume mddev, but T2 waits for open_mutex held by T1. Deadlock occurs.

Fix it by introducing a local mutex blk_holder_mutex to replace open_mutex.

Weakness

The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.

Affected Software

Extended Description

Locking is a type of synchronization behavior that ensures that multiple independently-operating processes or threads do not interfere with each other when accessing the same resource. All processes/threads are expected to follow the same steps for locking. If these steps are not followed precisely - or if no locking is done at all - then another process/thread could modify the shared resource in a way that is not visible or predictable to the original process. This can lead to data or memory corruption, denial of service, etc.

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/25.html
• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/27.html

References

• https://git.kernel.org/stable/c/03f12122b20b6e6028e9ed69030a49f9cffcbb75
• https://git.kernel.org/stable/c/1e5c5b0abaee7b62a10b9707a62083b71ad21f62
• https://git.kernel.org/stable/c/5a87c1f7993bc8ac358a3766bac5dc7126e01e98