Use After Free Affecting kernel-rt-modules-extra package, versions <0:5.14.0-427.35.1.el9_4

Note: Versions mentioned in the description apply only to the upstream kernel-rt-modules-extra package and not the kernel-rt-modules-extra package as distributed by AlmaLinux. See How to fix? for AlmaLinux:9 relevant fixed versions and status.

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

PCI/MSI: Fix UAF in msi_capability_init

KFENCE reports the following UAF:

BUG: KFENCE: use-after-free read in __pci_enable_msi_range+0x2c0/0x488

Use-after-free read at 0x0000000024629571 (in kfence-#12): __pci_enable_msi_range+0x2c0/0x488 pci_alloc_irq_vectors_affinity+0xec/0x14c pci_alloc_irq_vectors+0x18/0x28

kfence-#12: 0x0000000008614900-0x00000000e06c228d, size=104, cache=kmalloc-128

allocated by task 81 on cpu 7 at 10.808142s: __kmem_cache_alloc_node+0x1f0/0x2bc kmalloc_trace+0x44/0x138 msi_alloc_desc+0x3c/0x9c msi_domain_insert_msi_desc+0x30/0x78 msi_setup_msi_desc+0x13c/0x184 __pci_enable_msi_range+0x258/0x488 pci_alloc_irq_vectors_affinity+0xec/0x14c pci_alloc_irq_vectors+0x18/0x28

freed by task 81 on cpu 7 at 10.811436s: msi_domain_free_descs+0xd4/0x10c msi_domain_free_locked.part.0+0xc0/0x1d8 msi_domain_alloc_irqs_all_locked+0xb4/0xbc pci_msi_setup_msi_irqs+0x30/0x4c __pci_enable_msi_range+0x2a8/0x488 pci_alloc_irq_vectors_affinity+0xec/0x14c pci_alloc_irq_vectors+0x18/0x28

Descriptor allocation done in: __pci_enable_msi_range msi_capability_init msi_setup_msi_desc msi_insert_msi_desc msi_domain_insert_msi_desc msi_alloc_desc ...

Freed in case of failure in __msi_domain_alloc_locked() __pci_enable_msi_range msi_capability_init pci_msi_setup_msi_irqs msi_domain_alloc_irqs_all_locked msi_domain_alloc_locked __msi_domain_alloc_locked => fails msi_domain_free_locked ...

That failure propagates back to pci_msi_setup_msi_irqs() in msi_capability_init() which accesses the descriptor for unmasking in the error exit path.

Cure it by copying the descriptor and using the copy for the error exit path unmask operation.

[ tglx: Massaged change log ]

• https://errata.almalinux.org/9/ALSA-2024-6567.html
• https://access.redhat.com/security/cve/CVE-2024-41096
• https://access.redhat.com/errata/RHSA-2024:6567
• https://git.kernel.org/stable/c/0ae40b2d0a5de6b045504098e365d4fdff5bbeba
• https://git.kernel.org/stable/c/45fc8d20e0768ab0a0ad054081d0f68aa3c83976
• https://git.kernel.org/stable/c/9eee5330656bf92f51cb1f09b2dc9f8cf975b3d1
• https://git.kernel.org/stable/c/ff1121d2214b794dc1772081f27bdd90721a84bc