iio: event: Fix event FIFO reset race

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-64496
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-25 10:17:35 UTC
Updated2026-07-27 05:16:54 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 7.1 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

EPSS: 0.001260000 probability, percentile 0.026850000 (date 2026-07-29)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.1HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
3.1CNADECLARED7.1HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected b91accafbb1031b80d22ad83576877ff2f8b4774 9dc84ba4be5bbeb29ee49efe6cea2cb32c461424 git Not specified
CNA Linux Linux affected b91accafbb1031b80d22ad83576877ff2f8b4774 d16a702ca7d29c0b7a9b509339d1b044a1cadb32 git Not specified
CNA Linux Linux affected b91accafbb1031b80d22ad83576877ff2f8b4774 a13ef1adbc62085b21b546b07b0be7e2fbf52150 git Not specified
CNA Linux Linux affected b91accafbb1031b80d22ad83576877ff2f8b4774 0d4a646d7f87ea3625fafe387043fddc6a2f5e7f git Not specified
CNA Linux Linux affected b91accafbb1031b80d22ad83576877ff2f8b4774 72c6aa8e0d74eab91b8694cde97dec088c248fee git Not specified
CNA Linux Linux affected b91accafbb1031b80d22ad83576877ff2f8b4774 9edefd4c56bee3fe331e0355d1f10a533134999d git Not specified
CNA Linux Linux affected b91accafbb1031b80d22ad83576877ff2f8b4774 f187dc5a4c4846ffa07d9bda6e760837ed005574 git Not specified
CNA Linux Linux affected b91accafbb1031b80d22ad83576877ff2f8b4774 af791d295737ea6b6ff2c8d8488462a49c14af01 git Not specified
CNA Linux Linux affected 3.15 Not specified
CNA Linux Linux unaffected 3.15 semver Not specified
CNA Linux Linux unaffected 5.10.261 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.212 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.178 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.145 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.96 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.39 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.4 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/a13ef1adbc62085b21b546b07b0be7e2fbf52150 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d16a702ca7d29c0b7a9b509339d1b044a1cadb32 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0d4a646d7f87ea3625fafe387043fddc6a2f5e7f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f187dc5a4c4846ffa07d9bda6e760837ed005574 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/72c6aa8e0d74eab91b8694cde97dec088c248fee 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/af791d295737ea6b6ff2c8d8488462a49c14af01 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9dc84ba4be5bbeb29ee49efe6cea2cb32c461424 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9edefd4c56bee3fe331e0355d1f10a533134999d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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