CVE-2026-98832: blk-cgroup: save IRQ state in blkg_tryget_closest()

CVE-2026-98832: blk-cgroup: save IRQ state in blkg_tryget_closest()

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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

blk-cgroup: save IRQ state in blkg_tryget_closest()

bio_set_dev() associates the bio with a blkg through bio_associate_blkg().
If the blkg lookup misses, blkg_tryget_closest() takes q->queue_lock with
spin_lock_irq() and releases it with spin_unlock_irq(), which
unconditionally enables local interrupts.

Callers may call bio_set_dev() with interrupts already disabled, e.g.
dm-thin's pool_map() does so while holding pool->lock taken with
spin_lock_irq().  The nested spin_unlock_irq() then enables interrupts
while pool->lock is still held, so an I/O completion softirq can run on
the same CPU, re-acquire pool->lock (thin_endio(), or overwrite_endio()
-> complete_mapping_preparation()) and deadlock.  lockdep reports this
as inconsistent SOFTIRQ-ON-W to IN-SOFTIRQ-W usage.

Commit 3a762de55b4e ("block: save irq state in blkg_lookup_create()")
fixed the same problem while the lock lived in blkg_lookup_create(), but
commit 9327a865e395 ("blk-cgroup: don't nest queue_lock under rcu in
blkg_lookup_create()") moved the locking into blkg_tryget_closest() and
reverted it to spin_lock_irq().

Save and restore the caller's IRQ state instead.

The Linux kernel CVE team has assigned CVE-2026-98832 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 7.2 with commit 9327a865e395a53f67dffac4710beb1d4730495e and fixed in 7.2.10 with commit 9fcf4317384ce6758c3127a6e8914c54cbb9c8cc
	Issue introduced in 7.2 with commit 9327a865e395a53f67dffac4710beb1d4730495e and fixed in 7.3-rc6 with commit 327c428ba79b13e4cc5253333a9d5c0aa5579bdf

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-98832
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	block/blk-cgroup.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/9fcf4317384ce6758c3127a6e8914c54cbb9c8cc
	https://git.kernel.org/stable/c/327c428ba79b13e4cc5253333a9d5c0aa5579bdf