{"id":"CVE-2026-89777","published":"2026-09-16T09:17:08.073","lastModified":"2026-09-16T15:18:06.997","description":"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(struct perm_bits, GFP_KERNEL_ACCOUNT);\n\tif (!vdev->msi_perm)\n\t\treturn -ENOMEM;\n\n\tret = init_pci_cap_msi_perm(vdev->msi_perm, len, flags);\n\tif (ret) {\n\t\tkfree(vdev->msi_perm);\n\t\treturn ret;\t\t/* vdev->msi_perm left dangling */\n\t}\n\nWhen init_pci_cap_msi_perm() -> alloc_perm_bits() fails with -ENOMEM, the\nerror path frees vdev->msi_perm but leaves the freed pointer stored in\nit. vdev->msi_perm is not re-zeroed later because struct\nvfio_pci_core_device is per-device and persists across open/close cycles,\nand the vfio_config_init() error path returns without calling\nvfio_config_free(). So the dangling pointer outlives the failed open.\n\nThat leads to two use-after-frees on the same device:\n\n1. Reuse. The next vfio_config_init() sees the stale pointer at\n   \"if (vdev->msi_perm) return len;\" and reuses the freed object. MSI\n   config accesses in vfio_pci_config_rw_single() then dereference and\n   call the freed perm->readfn / perm->writefn function pointers.\n\n2. Double free. A later vfio_config_free() runs free_perm_bits() and\n   kfree() on the already-freed object.\n\nFix it by NULLing vdev->msi_perm after the kfree(), matching the\nNULL-after-free discipline already used in free_perm_bits() and\nvfio_config_free().\n\n  BUG: KASAN: slab-use-after-free in vfio_pci_config_rw_single (drivers/vfio/pci/vfio_pci_config.c:1961)\n  Read of size 8 at addr ffff88800fcc88d0 by task exploit/143\n  Call Trace:\n   ...\n   kasan_report (mm/kasan/report.c:595)\n   vfio_pci_config_rw_single (drivers/vfio/pci/vfio_pci_config.c:1961)\n   vfio_pci_config_rw (drivers/vfio/pci/vfio_pci_config.c:1986)\n   vfio_pci_rw (drivers/vfio/pci/vfio_pci_core.c:1599)\n   vfs_read (fs/read_write.c:572)\n   __x64_sys_pread64 (fs/read_write.c:764)\n   do_syscall_64 (arch/x86/entry/syscall_64.c:94)\n   ...\n\nFollowed on device close by a double free of the same object:\n\n  Oops: general protection fault, probably for non-canonical address\n    0x1f63e0e8000008: 0000 [#1] SMP KASAN NOPTI\n  RIP: 0010:kfree (mm/slub.c:6711)\n  Call Trace:\n   vfio_config_free (drivers/vfio/pci/vfio_pci_config.c:1861)\n   vfio_pci_core_disable (drivers/vfio/pci/vfio_pci_core.c:685)\n   vfio_pci_core_close_device (drivers/vfio/pci/vfio_pci_core.c:777)\n   vfio_df_close (drivers/vfio/vfio_main.c:602)\n   vfio_device_fops_release (drivers/vfio/vfio_main.c:648)\n   __fput (fs/file_table.c:512)\n   __x64_sys_close (fs/open.c:1496)\n   do_syscall_64 (arch/x86/entry/syscall_64.c:94)\n   ...\n  Kernel panic - not syncing: Fatal exception","cvssScore":8.8,"cvssSeverity":"HIGH","cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/25cdd2a492d868cff1e519a60fe282909c52d385","tags":[]},{"url":"https://git.kernel.org/stable/c/533d0c5feef85ee6404b9f41d5564fac6971a008","tags":[]},{"url":"https://git.kernel.org/stable/c/812f1db7f0755a19ef16ecdc5cec51bcabc5eda5","tags":[]},{"url":"https://git.kernel.org/stable/c/d665a1688af7f8fefd7c0eb04f2a37122ce007f4","tags":[]},{"url":"https://git.kernel.org/stable/c/dc77acfeb979dded39b247b60fef0399536bfa77","tags":[]},{"url":"https://git.kernel.org/stable/c/eb84cd81040e58dd05ac190f561f2115e3367249","tags":[]},{"url":"https://git.kernel.org/stable/c/f0eea8f9013676b42289ec35941e848b8a543e19","tags":[]},{"url":"https://git.kernel.org/stable/c/fda8fb7e8179561693a786a7af593f6b944a21c1","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}