Subject: CVE-2024-38385: genirq/irqdesc: Prevent use-after-free in irq_find_at_or_after()

From: Greg Kroah-Hartman <[email-masked]>

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

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

genirq/irqdesc: Prevent use-after-free in irq_find_at_or_after()

irq_find_at_or_after() dereferences the interrupt descriptor which is
returned by mt_find() while neither holding sparse_irq_lock nor RCU read
lock, which means the descriptor can be freed between mt_find() and the
dereference:

    CPU0                            CPU1
    desc = mt_find()
                                    delayed_free_desc(desc)
    irq_desc_get_irq(desc)

The use-after-free is reported by KASAN:

    Call trace:
     irq_get_next_irq+0x58/0x84
     show_stat+0x638/0x824
     seq_read_iter+0x158/0x4ec
     proc_reg_read_iter+0x94/0x12c
     vfs_read+0x1e0/0x2c8

    Freed by task 4471:
     slab_free_freelist_hook+0x174/0x1e0
     __kmem_cache_free+0xa4/0x1dc
     kfree+0x64/0x128
     irq_kobj_release+0x28/0x3c
     kobject_put+0xcc/0x1e0
     delayed_free_desc+0x14/0x2c
     rcu_do_batch+0x214/0x720

Guard the access with a RCU read lock section.

The Linux kernel CVE team has assigned CVE-2024-38385 to this issue.

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

	Issue introduced in 6.5 with commit 721255b9826b and fixed in 6.6.34 with commit 1c7891812d85
	Issue introduced in 6.5 with commit 721255b9826b and fixed in 6.9.5 with commit d084aa022f84
	Issue introduced in 6.5 with commit 721255b9826b and fixed in 6.10 with commit b84a8aba8062

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-2024-38385
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:
	kernel/irq/irqdesc.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/1c7891812d85500ae2ca4051fa5683fcf29930d8
	https://git.kernel.org/stable/c/d084aa022f84319f8079e30882cbcbc026af9f21
	https://git.kernel.org/stable/c/b84a8aba806261d2f759ccedf4a2a6a80a5e55ba