fanotify: fix use-after-free of file range info

Summary

In the Linux kernel, the following vulnerability has been resolved: fanotify: fix use-after-free of file range info fsnotify_pre_content() builds its file_range on the triggering task's stack. fanotify_alloc_perm_event() saves a pointer to range.pos in the heap-allocated permission event so copy_range_info_to_user() can report the offset later. The event reader can set the event state to FAN_EVENT_REPORTED and then sleep while preparing the file descriptor. If a signal interrupts the triggering task at that point, fanotify_get_response() changes the state to FAN_EVENT_CANCELED and returns. This unwinds the file_range stack frame while the reader still owns the event. The reader then dereferences pevent->ppos and copies the stale stack value to userspace. KASAN reported: BUG: KASAN: use-after-free in fanotify_read+0x293e/0x2970 Read of size 8 at addr ffff88811434fc50 by task fanotify_inotif/95 Call Trace: fanotify_read+0x293e/0x2970 vfs_read+0x177/0xa20 ksys_read+0xf7/0x1c0 do_syscall_64+0xf9/0x540 entry_SYSCALL_64_after_hwframe+0x77/0x7f Store the range position directly in the permission event and use FANOTIFY_NO_RANGE when range information is unavailable. The event remains alive until the reader finishes, so the reported offset no longer depends on the triggering task's stack.

Timeline

1. Sep 11, 2026, 7:45 PM UTCCVE published
2. Oct 19, 2026, 8:49 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 870499bc1d4dc04cba1f63dd5e7bc02b983e2458 · fixed in 66aa9a9e6481bfa512ee5b6380eaaec455a954d2; From 870499bc1d4dc04cba1f63dd5e7bc02b983e2458 · fixed in b8f73b163b646bc56d4dce9c697a578e333f4894; From 870499bc1d4dc04cba1f63dd5e7bc02b983e2458 · fixed in d7f1cf5be33ef0175a4e8ed8687aeb98fb00a851

• Linux Linux

  6.14

• KernelLinux

  From 6.14.0 · fixed in 6.18.50; From 6.19.0 · fixed in 7.2.4

References 3