CVE-2026-90185null_blk: serialize configfs attribute stores with the lock

Official description

In the Linux kernel, the following vulnerability has been resolved: null_blk: serialize configfs attribute stores with the lock The NULLB_DEVICE_ATTR _store takes no lock: apply_fn attributes (submit_queues, poll_queues) get dev->NAME written again after apply_fn returns, outside its lock; APPLY=NULL attributes are entirely lockless. configfs only serializes stores per-open-file, so concurrent stores on separate fds race. For apply_fn attributes, once one store's apply_fn has reconfigured the hardware, a second (losing) store can still overwrite dev->NAME afterwards. This leaves dev->submit_queues out of sync with the live queue count, which is later caught by the WARN_ON_ONCE() in null_map_queues(). For !apply_fn attributes, power_store()'s null_add_dev() validates and builds the device under "lock" but only sets CONFIGURED afterwards. A store slipping in during this window can change a field mid-setup -- for example, zone_nr_conv can be pushed above nr_zones after it has already been clamped, leading to an out-of-bounds dev->zones[] access. Take "lock" in the macro around the apply_fn call, the CONFIGURED test and the field write, and move it out of nullb_apply_submit_queues()/ nullb_apply_poll_queues() so both paths are covered once. This serializes stores with power_store's setup and with each other.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/8e839ed5210399a0330a8a6c5885c1d40a537c6d
• https://git.kernel.org/stable/c/88d806d0e1d36246208386a8e55b511c1b3d647c
• https://git.kernel.org/stable/c/3945ce8cbce4e328e6fdf0b522dc71e340de19db
• https://git.kernel.org/stable/c/65cae82fd3c39b53430672cb9e3ecd267471a6ce
• https://git.kernel.org/stable/c/c70994c2862b05e44728912b2ea9487d31e2aea7
• https://git.kernel.org/stable/c/7e7fff51808237703a3a1df6dd5cae1dfd1db86d