---
id: CVE-2026-89777
title: "In the Linux kernel, the following vulnerability has been resolved:\n\nvfio/pci: clear vdev->msi_perm after freeing it on init failure\n\nvfio_msi_cap_len() lazily allocates the per-device MSI permission table:\n\n\tvdev->msi_perm = kmalloc_obj…"
summary: "In the Linux kernel, the following vulnerability has been resolved:\n\nvfio/pci: clear vdev->msi_perm after freeing it on init failure\n\nvfio_msi_cap_len() lazily allocates the per-device MSI permission table:\n\n\tvdev->msi_perm = kmalloc_obj…"
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 30ea32ab1951c80c6113f300fce2c70cd12659e4 <
    eb84cd81040e58dd05ac190f561f2115e3367249
  - >-
    Linux >= 30ea32ab1951c80c6113f300fce2c70cd12659e4 <
    f0eea8f9013676b42289ec35941e848b8a543e19
  - >-
    Linux >= 30ea32ab1951c80c6113f300fce2c70cd12659e4 <
    d665a1688af7f8fefd7c0eb04f2a37122ce007f4
  - >-
    Linux >= 30ea32ab1951c80c6113f300fce2c70cd12659e4 <
    25cdd2a492d868cff1e519a60fe282909c52d385
  - >-
    Linux >= 30ea32ab1951c80c6113f300fce2c70cd12659e4 <
    812f1db7f0755a19ef16ecdc5cec51bcabc5eda5
  - >-
    Linux >= 30ea32ab1951c80c6113f300fce2c70cd12659e4 <
    533d0c5feef85ee6404b9f41d5564fac6971a008
  - >-
    Linux >= 30ea32ab1951c80c6113f300fce2c70cd12659e4 <
    fda8fb7e8179561693a786a7af593f6b944a21c1
  - >-
    Linux >= 30ea32ab1951c80c6113f300fce2c70cd12659e4 <
    dc77acfeb979dded39b247b60fef0399536bfa77
  - Linux ac370e3d1f3b01519d2705cd5815d1c9d0a8812b
  - Linux be363e27ec3c3a99793da2be6c07eafb95709c6b
  - Linux f1b10ba5739440ca51d66f0b2949cead88d2dd02
  - Linux dde3433de9a067a33d67d65b9093cad3e043e49e
  - Linux >= 4.4.203 < 4.5
  - Linux >= 4.9.203 < 4.10
  - Linux >= 4.14.155 < 4.15
  - Linux >= 4.19.85 < 4.20
  - Linux 4.20
published: '2026-09-16'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T15:18:06.997'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89777'
references:
  - url: 'https://git.kernel.org/stable/c/25cdd2a492d868cff1e519a60fe282909c52d385'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/533d0c5feef85ee6404b9f41d5564fac6971a008'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/812f1db7f0755a19ef16ecdc5cec51bcabc5eda5'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d665a1688af7f8fefd7c0eb04f2a37122ce007f4'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/dc77acfeb979dded39b247b60fef0399536bfa77'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/eb84cd81040e58dd05ac190f561f2115e3367249'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/f0eea8f9013676b42289ec35941e848b8a543e19'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/fda8fb7e8179561693a786a7af593f6b944a21c1'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-16T08:52:29.599Z'
epss: 0.00171
epssPercentile: 0.05718
---

## Overview

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

vfio/pci: clear vdev->msi_perm after freeing it on init failure

vfio_msi_cap_len() lazily allocates the per-device MSI permission table:

	vdev->msi_perm = kmalloc_obj(struct perm_bits, GFP_KERNEL_ACCOUNT);
	if (!vdev->msi_perm)
		return -ENOMEM;

	ret = init_pci_cap_msi_perm(vdev->msi_perm, len, flags);
	if (ret) {
		kfree(vdev->msi_perm);
		return ret;		/* vdev->msi_perm left dangling */
	}

When init_pci_cap_msi_perm() -> alloc_perm_bits() fails with -ENOMEM, the
error path frees vdev->msi_perm but leaves the freed pointer stored in
it. vdev->msi_perm is not re-zeroed later because struct
vfio_pci_core_device is per-device and persists across open/close cycles,
and the vfio_config_init() error path returns without calling
vfio_config_free(). So the dangling pointer outlives the failed open.

That leads to two use-after-frees on the same device:

1. Reuse. The next vfio_config_init() sees the stale pointer at
   "if (vdev->msi_perm) return len;" and reuses the freed object. MSI
   config accesses in vfio_pci_config_rw_single() then dereference and
   call the freed perm->readfn / perm->writefn function pointers.

2. Double free. A later vfio_config_free() runs free_perm_bits() and
   kfree() on the already-freed object.

Fix it by NULLing vdev->msi_perm after the kfree(), matching the
NULL-after-free discipline already used in free_perm_bits() and
vfio_config_free().

  BUG: KASAN: slab-use-after-free in vfio_pci_config_rw_single (drivers/vfio/pci/vfio_pci_config.c:1961)
  Read of size 8 at addr ffff88800fcc88d0 by task exploit/143
  Call Trace:
   ...
   kasan_report (mm/kasan/report.c:595)
   vfio_pci_config_rw_single (drivers/vfio/pci/vfio_pci_config.c:1961)
   vfio_pci_config_rw (drivers/vfio/pci/vfio_pci_config.c:1986)
   vfio_pci_rw (drivers/vfio/pci/vfio_pci_core.c:1599)
   vfs_read (fs/read_write.c:572)
   __x64_sys_pread64 (fs/read_write.c:764)
   do_syscall_64 (arch/x86/entry/syscall_64.c:94)
   ...

Followed on device close by a double free of the same object:

  Oops: general protection fault, probably for non-canonical address
    0x1f63e0e8000008: 0000 [#1] SMP KASAN NOPTI
  RIP: 0010:kfree (mm/slub.c:6711)
  Call Trace:
   vfio_config_free (drivers/vfio/pci/vfio_pci_config.c:1861)
   vfio_pci_core_disable (drivers/vfio/pci/vfio_pci_core.c:685)
   vfio_pci_core_close_device (drivers/vfio/pci/vfio_pci_core.c:777)
   vfio_df_close (drivers/vfio/vfio_main.c:602)
   vfio_device_fops_release (drivers/vfio/vfio_main.c:648)
   __fput (fs/file_table.c:512)
   __x64_sys_close (fs/open.c:1496)
   do_syscall_64 (arch/x86/entry/syscall_64.c:94)
   ...
  Kernel panic - not syncing: Fatal exception

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.