CVE-2024-56755 Information

Description

In the Linux kernel the following vulnerability has been resolved:

netfs/fscache: Add a memory barrier for FSCACHE_VOLUME_CREATING

In fscache_create_volume() there is a missing memory barrier between the bit-clearing operation and the wake-up operation. This may cause a situation where after a wake-up the bit-clearing operation hasn’t been detected yet leading to an indefinite wait. The triggering process is as follows:

[cookie1] [cookie2] [volume_work] fscache_perform_lookup fscache_create_volume fscache_perform_lookup fscache_create_volume fscache_create_volume_work cachefiles_acquire_volume clear_and_wake_up_bit test_and_set_bit test_and_set_bit goto maybe_wait goto no_wait

In the above process cookie1 and cookie2 has the same volume. When cookie1 enters the -no_wait- process it will clear the bit and wake up the waiting process. If a barrier is missing it may cause cookie2 to remain in the -wait- process indefinitely.

In commit 3288666c7256 (scache: Use clear_and_wake_up_bit() in fscache_create_volume_work()) barriers were added to similar operations in fscache_create_volume_work() but fscache_create_volume() was missed.

By combining the clear and wake operations into clear_and_wake_up_bit() to fix this issue.

Reference

https://git.kernel.org/stable/c/22f9400a6f3560629478e0a64247b8fcc811a24d https://git.kernel.org/stable/c/539fabba965e119b98066fc6ba5257b5eaf4eda2 https://git.kernel.org/stable/c/8beb682cc9a0798a280bbb95e3e41617237090b2 https://git.kernel.org/stable/c/8cc1df3113cb71a0df2c46dd5b102c9e11c8a8c6 https://git.kernel.org/stable/c/ddab02607eed9e415dc62fde421d4329e5345315