Subject: CVE-2024-41096: PCI/MSI: Fix UAF in msi_capability_init

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

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

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 ]

The Linux kernel CVE team has assigned CVE-2024-41096 to this issue.

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

	Issue introduced in 5.17 with commit bf6e054e0e3f and fixed in 6.1.109 with commit 0ae40b2d0a5d
	Issue introduced in 5.17 with commit bf6e054e0e3f and fixed in 6.6.37 with commit ff1121d2214b
	Issue introduced in 5.17 with commit bf6e054e0e3f and fixed in 6.9.8 with commit 45fc8d20e076
	Issue introduced in 5.17 with commit bf6e054e0e3f and fixed in 6.10 with commit 9eee5330656b

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-2024-41096
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:
	drivers/pci/msi/msi.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/0ae40b2d0a5de6b045504098e365d4fdff5bbeba
	https://git.kernel.org/stable/c/ff1121d2214b794dc1772081f27bdd90721a84bc
	https://git.kernel.org/stable/c/45fc8d20e0768ab0a0ad054081d0f68aa3c83976
	https://git.kernel.org/stable/c/9eee5330656bf92f51cb1f09b2dc9f8cf975b3d1