CVE-2022-48801

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

iio: buffer: Fix file related error handling in IIO_BUFFER_GET_FD_IOCTL

If we fail to copy the just created file descriptor to userland, we try to clean up by putting back fd and freeing ib. The code uses put_unused_fd() for the former which is wrong, as the file descriptor was already published by fd_install() which gets called internally by anon_inode_getfd().

This makes the error handling code leaving a half cleaned up file descriptor table around and a partially destructed file object, allowing userland to play use-after-free tricks on us, by abusing the still usable fd and making the code operate on a dangling file->private_data pointer.

Instead of leaving the kernel in a partially corrupted state, dont attempt to explicitly clean up and leave this to the process exit path thatll release any still valid fds, including the one created by the previous call to anon_inode_getfd(). Simply return -EFAULT to indicate the error.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/202071d2518537866d291aa7cf26af54e674f4d4
• https://git.kernel.org/stable/c/b7f54894aa7517d2b6c797a499b9f491e9db9083
• https://git.kernel.org/stable/c/c72ea20503610a4a7ba26c769357d31602769c01
• https://git.kernel.org/stable/c/202071d2518537866d291aa7cf26af54e674f4d4
• https://git.kernel.org/stable/c/b7f54894aa7517d2b6c797a499b9f491e9db9083
• https://git.kernel.org/stable/c/c72ea20503610a4a7ba26c769357d31602769c01