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CVE-2026-64496

iio: event: Fix event FIFO reset race

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.96, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: partial

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 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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: partial

  3. Record last updated

Affected versions

  • Linux Linux

    From b91accafbb1031b80d22ad83576877ff2f8b4774 · fixed in 9dc84ba4be5bbeb29ee49efe6cea2cb32c461424; From b91accafbb1031b80d22ad83576877ff2f8b4774 · fixed in d16a702ca7d29c0b7a9b509339d1b044a1cadb32; From b91accafbb1031b80d22ad83576877ff2f8b4774 · fixed in a13ef1adbc62085b21b546b07b0be7e2fbf52150; From b91accafbb1031b80d22ad83576877ff2f8b4774 · fixed in 0d4a646d7f87ea3625fafe387043fddc6a2f5e7f; From b91accafbb1031b80d22ad83576877ff2f8b4774 · fixed in 72c6aa8e0d74eab91b8694cde97dec088c248fee; From b91accafbb1031b80d22ad83576877ff2f8b4774 · fixed in 9edefd4c56bee3fe331e0355d1f10a533134999d; From b91accafbb1031b80d22ad83576877ff2f8b4774 · fixed in f187dc5a4c4846ffa07d9bda6e760837ed005574; From b91accafbb1031b80d22ad83576877ff2f8b4774 · fixed in af791d295737ea6b6ff2c8d8488462a49c14af01

  • Linux Linux

    3.15

  • KernelLinux

    From 3.15.0 · fixed in 5.10.261; From 5.11.0 · fixed in 5.15.212; From 5.16.0 · fixed in 6.1.178; From 6.2.0 · fixed in 6.6.145; From 6.7.0 · fixed in 6.12.96; From 6.13.0 · fixed in 6.18.39; From 6.19.0 · fixed in 7.1.4

References 8

git.kernel.org