Use After Free Affecting kernel-rt package, versions *

Note: Versions mentioned in the description apply only to the upstream kernel-rt package and not the kernel-rt package as distributed by RHEL. See How to fix? for RHEL:7 relevant fixed versions and status.

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.

• https://access.redhat.com/security/cve/CVE-2024-38385
• https://git.kernel.org/stable/c/1c7891812d85500ae2ca4051fa5683fcf29930d8
• https://git.kernel.org/stable/c/b84a8aba806261d2f759ccedf4a2a6a80a5e55ba
• https://git.kernel.org/stable/c/d084aa022f84319f8079e30882cbcbc026af9f21