CVE-2026-64496

Status: UPDATED  |  Advisory ID: CVE-2026-64496

Key Details

Affected Products, Subsystems & Sectors

What to Know

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. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References