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CVE-2026-89777

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

Description (CNA)

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

Affected (CNA)

Vendor / productVersions
Linux / Linuxaffected 30ea32ab1951c80c6113f300fce2c70cd12659e4 before eb84cd81040e58dd05ac190f561f2115e3367249; affected 30ea32ab1951c80c6113f300fce2c70cd12659e4 before f0eea8f9013676b42289ec35941e848b8a543e19; affected 30ea32ab1951c80c6113f300fce2c70cd12659e4 before d665a1688af7f8fefd7c0eb04f2a37122ce007f4; affected 30ea32ab1951c80c6113f300fce2c70cd12659e4 before 25cdd2a492d868cff1e519a60fe282909c52d385; affected 30ea32ab1951c80c6113f300fce2c70cd12659e4 before 812f1db7f0755a19ef16ecdc5cec51bcabc5eda5; affected 30ea32ab1951c80c6113f300fce2c70cd12659e4 before 533d0c5feef85ee6404b9f41d5564fac6971a008; affected 30ea32ab1951c80c6113f300fce2c70cd12659e4 before fda8fb7e8179561693a786a7af593f6b944a21c1; affected 30ea32ab1951c80c6113f300fce2c70cd12659e4 before dc77acfeb979dded39b247b60fef0399536bfa77; affected ac370e3d1f3b01519d2705cd5815d1c9d0a8812b; affected be363e27ec3c3a99793da2be6c07eafb95709c6b; affected f1b10ba5739440ca51d66f0b2949cead88d2dd02; affected dde3433de9a067a33d67d65b9093cad3e043e49e; affected 4.4.203 before 4.5; affected 4.9.203 before 4.10; affected 4.14.155 before 4.15; affected 4.19.85 before 4.20
Linux / Linuxaffected 4.20; unaffected 0 before 4.20; unaffected 5.10.270 through 5.10.*; unaffected 5.15.221 through 5.15.*; unaffected 6.1.188 through 6.1.*; unaffected 6.6.157 through 6.6.*; unaffected 6.12.110 through 6.12.*; unaffected 6.18.52 through 6.18.*; unaffected 7.2.6 through 7.2.*; unaffected 7.3 through *

CWE

No CWE identifiers supplied.

References