CVE-2022-49406

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

block: Fix potential deadlock in blk_ia_range_sysfs_show()

When being read, a sysfs attribute is already protected against removal with the kobject node active reference counter. As a result, in blk_ia_range_sysfs_show(), there is no need to take the queue sysfs lock when reading the value of a range attribute. Using the queue sysfs lock in this function creates a potential deadlock situation with the disk removal, something that a lockdep signals with a splat when the device is removed:

[ 760.703551] Possible unsafe locking scenario: [ 760.703551] [ 760.703554] CPU0 CPU1 [ 760.703556] —- —- [ 760.703558] lock(&q->sysfs_lock); [ 760.703565] lock(kn->active#385); [ 760.703573] lock(&q->sysfs_lock); [ 760.703579] lock(kn->active#385); [ 760.703587] [ 760.703587] *** DEADLOCK ***

Solve this by removing the mutex_lock()/mutex_unlock() calls from blk_ia_range_sysfs_show().

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/41e46b3c2aa24f755b2ae9ec4ce931ba5f0d8532
• https://git.kernel.org/stable/c/717b078bc745ba9a262abebed9806a17e8bbb77b
• https://git.kernel.org/stable/c/dc107c805cde709866b59867ef72b9390199205e