CVE-2026-89777 is a vulnerability in Linux Kernel
Published on September 16, 2026
vfio/pci: clear vdev->msi_perm after freeing it on init failure
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
Products Associated with CVE-2026-89777
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Affected Versions
Linux:- Version 30ea32ab1951c80c6113f300fce2c70cd12659e4 and below eb84cd81040e58dd05ac190f561f2115e3367249 is affected.
- Version 30ea32ab1951c80c6113f300fce2c70cd12659e4 and below f0eea8f9013676b42289ec35941e848b8a543e19 is affected.
- Version 30ea32ab1951c80c6113f300fce2c70cd12659e4 and below d665a1688af7f8fefd7c0eb04f2a37122ce007f4 is affected.
- Version 30ea32ab1951c80c6113f300fce2c70cd12659e4 and below 25cdd2a492d868cff1e519a60fe282909c52d385 is affected.
- Version 30ea32ab1951c80c6113f300fce2c70cd12659e4 and below 812f1db7f0755a19ef16ecdc5cec51bcabc5eda5 is affected.
- Version 30ea32ab1951c80c6113f300fce2c70cd12659e4 and below 533d0c5feef85ee6404b9f41d5564fac6971a008 is affected.
- Version 30ea32ab1951c80c6113f300fce2c70cd12659e4 and below fda8fb7e8179561693a786a7af593f6b944a21c1 is affected.
- Version 30ea32ab1951c80c6113f300fce2c70cd12659e4 and below dc77acfeb979dded39b247b60fef0399536bfa77 is affected.
- Version ac370e3d1f3b01519d2705cd5815d1c9d0a8812b is affected.
- Version be363e27ec3c3a99793da2be6c07eafb95709c6b is affected.
- Version f1b10ba5739440ca51d66f0b2949cead88d2dd02 is affected.
- Version dde3433de9a067a33d67d65b9093cad3e043e49e is affected.
- Version 4.4.203 and below 4.5 is affected.
- Version 4.9.203 and below 4.10 is affected.
- Version 4.14.155 and below 4.15 is affected.
- Version 4.19.85 and below 4.20 is affected.
- Version 4.20 is affected.
- Before 4.20 is unaffected.
- Version 5.10.270, <= 5.10.* is unaffected.
- Version 5.15.221, <= 5.15.* is unaffected.
- Version 6.1.188, <= 6.1.* is unaffected.
- Version 6.6.157, <= 6.6.* is unaffected.
- Version 6.12.110, <= 6.12.* is unaffected.
- Version 6.18.52, <= 6.18.* is unaffected.
- Version 7.2.6, <= 7.2.* is unaffected.
- Version 7.3-rc1, <= * is unaffected.