linux-cve-announce - CVE-2023-52779: fs: Pass AT_GETATTR_NOSEC flag to getattr interface function

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Message-ID: <2024052153-CVE-2023-52779-59e8@gregkh>
Date: Tue, 21 May 2024 17:31:15 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2023-52779: fs: Pass AT_GETATTR_NOSEC flag to getattr interface function

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

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

fs: Pass AT_GETATTR_NOSEC flag to getattr interface function

When vfs_getattr_nosec() calls a filesystem's getattr interface function
then the 'nosec' should propagate into this function so that
vfs_getattr_nosec() can again be called from the filesystem's gettattr
rather than vfs_getattr(). The latter would add unnecessary security
checks that the initial vfs_getattr_nosec() call wanted to avoid.
Therefore, introduce the getattr flag GETATTR_NOSEC and allow to pass
with the new getattr_flags parameter to the getattr interface function.
In overlayfs and ecryptfs use this flag to determine which one of the
two functions to call.

In a recent code change introduced to IMA vfs_getattr_nosec() ended up
calling vfs_getattr() in overlayfs, which in turn called
security_inode_getattr() on an exiting process that did not have
current->fs set anymore, which then caused a kernel NULL pointer
dereference. With this change the call to security_inode_getattr() can
be avoided, thus avoiding the NULL pointer dereference.

The Linux kernel CVE team has assigned CVE-2023-52779 to this issue.

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

	Issue introduced in 6.5 with commit db1d1e8b9867 and fixed in 6.6.4 with commit 3fb0fa086419
	Issue introduced in 6.5 with commit db1d1e8b9867 and fixed in 6.7 with commit 8a924db2d7b5

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-2023-52779
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:
	fs/ecryptfs/inode.c
	fs/overlayfs/inode.c
	fs/overlayfs/overlayfs.h
	fs/stat.c
	include/uapi/linux/fcntl.h

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/3fb0fa08641903304b9d81d52a379ff031dc41d4
	https://git.kernel.org/stable/c/8a924db2d7b5eb69ba08b1a0af46e9f1359a9bdf