Subject: CVE-2022-48801: iio: buffer: Fix file related error handling in IIO_BUFFER_GET_FD_IOCTL

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

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, don't
attempt to explicitly clean up and leave this to the process exit
path that'll release any still valid fds, including the one created
by the previous call to anon_inode_getfd(). Simply return -EFAULT to
indicate the error.

The Linux kernel CVE team has assigned CVE-2022-48801 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.13 with commit f73f7f4da581 and fixed in 5.15.24 with commit b7f54894aa75
	Issue introduced in 5.13 with commit f73f7f4da581 and fixed in 5.16.10 with commit 202071d25185
	Issue introduced in 5.13 with commit f73f7f4da581 and fixed in 5.17 with commit c72ea2050361

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2022-48801
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/iio/industrialio-buffer.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/b7f54894aa7517d2b6c797a499b9f491e9db9083
	https://git.kernel.org/stable/c/202071d2518537866d291aa7cf26af54e674f4d4
	https://git.kernel.org/stable/c/c72ea20503610a4a7ba26c769357d31602769c01