CVE-2024-56755netfs/fscache: Add a memory barrier for FSCACHE_VOLUME_CREATING

Official 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 ("fscache: 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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/ddab02607eed9e415dc62fde421d4329e5345315
• 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/22f9400a6f3560629478e0a64247b8fcc811a24d
• https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html