{"id":"CVE-2026-64496","summary":"iio: event: Fix event FIFO reset race","details":"In the Linux kernel, the following vulnerability has been resolved:\n\niio: event: Fix event FIFO reset race\n\n`iio_event_getfd()` creates the event file descriptor with\n`anon_inode_getfd()`, which allocates a new fd, creates the anonymous\nfile and installs it in the process fd table before returning to the\ncaller.\n\nThe IIO code resets the event FIFO after `anon_inode_getfd()` has returned,\nbut before `IIO_GET_EVENT_FD_IOCTL` has copied the fd number to userspace.\nBut since fd tables are shared between threads, another thread can guess\nthe newly allocated fd number and issue a `read()` on it as soon as the fd\nhas been installed.\n\nThis means the `kfifo_to_user()` in `iio_event_chrdev_read()` can run in\nparallel with the `kfifo_reset_out()` in `iio_event_getfd()`.\n\nThe kfifo documentation says that `kfifo_reset_out()` is only safe when it\nis called from the reader thread and there is only one concurrent reader.\nOtherwise it is dangerous and must be handled in the same way as\n`kfifo_reset()`.\n\nIf that happens, `kfifo_to_user()` can advance the FIFO `out` index based\non state from before the reset, after the reset has already moved the `out`\nindex to the current `in` index. That can leave the FIFO with an `out`\nindex past the `in` index. A later `read()` can then see an underflowed\nFIFO length and copy more data than the event FIFO buffer contains. This\ncan result in an out-of-bounds read and leak adjacent kernel memory to\nuserspace.\n\nMove the FIFO reset before `anon_inode_getfd()`. At that point the event fd is\nmarked busy, but the new fd has not been installed yet, so userspace cannot\naccess it while the FIFO is reset.","modified":"2026-08-12T11:57:07.456624458Z","published":"2026-07-25T08:51:53.194Z","related":["ALSA-2026:52761","ALSA-2026:52765","openSUSE-SU-2026:11476-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64496.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0d4a646d7f87ea3625fafe387043fddc6a2f5e7f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/72c6aa8e0d74eab91b8694cde97dec088c248fee"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9dc84ba4be5bbeb29ee49efe6cea2cb32c461424"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9edefd4c56bee3fe331e0355d1f10a533134999d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a13ef1adbc62085b21b546b07b0be7e2fbf52150"},{"type":"WEB","url":"https://git.kernel.org/stable/c/af791d295737ea6b6ff2c8d8488462a49c14af01"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d16a702ca7d29c0b7a9b509339d1b044a1cadb32"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f187dc5a4c4846ffa07d9bda6e760837ed005574"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64496.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64496"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"b91accafbb1031b80d22ad83576877ff2f8b4774"},{"fixed":"9dc84ba4be5bbeb29ee49efe6cea2cb32c461424"},{"fixed":"d16a702ca7d29c0b7a9b509339d1b044a1cadb32"},{"fixed":"a13ef1adbc62085b21b546b07b0be7e2fbf52150"},{"fixed":"0d4a646d7f87ea3625fafe387043fddc6a2f5e7f"},{"fixed":"72c6aa8e0d74eab91b8694cde97dec088c248fee"},{"fixed":"9edefd4c56bee3fe331e0355d1f10a533134999d"},{"fixed":"f187dc5a4c4846ffa07d9bda6e760837ed005574"},{"fixed":"af791d295737ea6b6ff2c8d8488462a49c14af01"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-64496.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.15.0"},{"fixed":"5.10.261"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.212"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.178"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.145"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.96"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.39"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.4"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-64496.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H"}]}