---
id: CVE-2026-64496
title: 'iio: event: Fix event FIFO reset race'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  iio: event: Fix event FIFO reset race

  `iio_event_getfd()` creates the event file descriptor with
  `anon_inode_getfd()`, which allocates a new fd, creates the anonymous
  …
severity: high
cvss: 7.1
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= b91accafbb1031b80d22ad83576877ff2f8b4774 <
    9dc84ba4be5bbeb29ee49efe6cea2cb32c461424
  - >-
    Linux >= b91accafbb1031b80d22ad83576877ff2f8b4774 <
    d16a702ca7d29c0b7a9b509339d1b044a1cadb32
  - >-
    Linux >= b91accafbb1031b80d22ad83576877ff2f8b4774 <
    a13ef1adbc62085b21b546b07b0be7e2fbf52150
  - >-
    Linux >= b91accafbb1031b80d22ad83576877ff2f8b4774 <
    0d4a646d7f87ea3625fafe387043fddc6a2f5e7f
  - >-
    Linux >= b91accafbb1031b80d22ad83576877ff2f8b4774 <
    72c6aa8e0d74eab91b8694cde97dec088c248fee
  - >-
    Linux >= b91accafbb1031b80d22ad83576877ff2f8b4774 <
    9edefd4c56bee3fe331e0355d1f10a533134999d
  - >-
    Linux >= b91accafbb1031b80d22ad83576877ff2f8b4774 <
    f187dc5a4c4846ffa07d9bda6e760837ed005574
  - >-
    Linux >= b91accafbb1031b80d22ad83576877ff2f8b4774 <
    af791d295737ea6b6ff2c8d8488462a49c14af01
  - Linux 3.15
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-16T15:41:26.474365Z'
published: '2026-07-25'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:42:38.605Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-64496'
references:
  - url: 'https://git.kernel.org/stable/c/9dc84ba4be5bbeb29ee49efe6cea2cb32c461424'
  - url: 'https://git.kernel.org/stable/c/d16a702ca7d29c0b7a9b509339d1b044a1cadb32'
  - url: 'https://git.kernel.org/stable/c/a13ef1adbc62085b21b546b07b0be7e2fbf52150'
  - url: 'https://git.kernel.org/stable/c/0d4a646d7f87ea3625fafe387043fddc6a2f5e7f'
  - url: 'https://git.kernel.org/stable/c/72c6aa8e0d74eab91b8694cde97dec088c248fee'
  - url: 'https://git.kernel.org/stable/c/9edefd4c56bee3fe331e0355d1f10a533134999d'
  - url: 'https://git.kernel.org/stable/c/f187dc5a4c4846ffa07d9bda6e760837ed005574'
  - url: 'https://git.kernel.org/stable/c/af791d295737ea6b6ff2c8d8488462a49c14af01'
tags:
  - cve.org
epss: 0.00126
epssPercentile: 0.02066
ingestedAt: '2026-10-16T17:24:46.823Z'
---

## Overview

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

iio: event: Fix event FIFO reset race

`iio_event_getfd()` creates the event file descriptor with
`anon_inode_getfd()`, which allocates a new fd, creates the anonymous
file and installs it in the process fd table before returning to the
caller.

The IIO code resets the event FIFO after `anon_inode_getfd()` has returned,
but before `IIO_GET_EVENT_FD_IOCTL` has copied the fd number to userspace.
But since fd tables are shared between threads, another thread can guess
the newly allocated fd number and issue a `read()` on it as soon as the fd
has been installed.

This means the `kfifo_to_user()` in `iio_event_chrdev_read()` can run in
parallel with the `kfifo_reset_out()` in `iio_event_getfd()`.

The kfifo documentation says that `kfifo_reset_out()` is only safe when it
is called from the reader thread and there is only one concurrent reader.
Otherwise it is dangerous and must be handled in the same way as
`kfifo_reset()`.

If that happens, `kfifo_to_user()` can advance the FIFO `out` index based
on state from before the reset, after the reset has already moved the `out`
index to the current `in` index. That can leave the FIFO with an `out`
index past the `in` index. A later `read()` can then see an underflowed
FIFO length and copy more data than the event FIFO buffer contains. This
can result in an out-of-bounds read and leak adjacent kernel memory to
userspace.

Move the FIFO reset before `anon_inode_getfd()`. At that point the event fd is
marked busy, but the new fd has not been installed yet, so userspace cannot
access it while the FIFO is reset.

## Affected

- `Linux >= b91accafbb1031b80d22ad83576877ff2f8b4774 < 9dc84ba4be5bbeb29ee49efe6cea2cb32c461424`
- `Linux >= b91accafbb1031b80d22ad83576877ff2f8b4774 < d16a702ca7d29c0b7a9b509339d1b044a1cadb32`
- `Linux >= b91accafbb1031b80d22ad83576877ff2f8b4774 < a13ef1adbc62085b21b546b07b0be7e2fbf52150`
- `Linux >= b91accafbb1031b80d22ad83576877ff2f8b4774 < 0d4a646d7f87ea3625fafe387043fddc6a2f5e7f`
- `Linux >= b91accafbb1031b80d22ad83576877ff2f8b4774 < 72c6aa8e0d74eab91b8694cde97dec088c248fee`
- `Linux >= b91accafbb1031b80d22ad83576877ff2f8b4774 < 9edefd4c56bee3fe331e0355d1f10a533134999d`
- `Linux >= b91accafbb1031b80d22ad83576877ff2f8b4774 < f187dc5a4c4846ffa07d9bda6e760837ed005574`
- `Linux >= b91accafbb1031b80d22ad83576877ff2f8b4774 < af791d295737ea6b6ff2c8d8488462a49c14af01`
- `Linux 3.15`

## Remediation

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