linux-cve-announce - CVE-2023-53260: ovl: fix null pointer dereference in ovl

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Message-ID: <2025091504-CVE-2023-53260-2323@gregkh>
Date: Mon, 15 Sep 2025 16:46:35 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53260: ovl: fix null pointer dereference in ovl_permission()

From: Greg Kroah-Hartman <gregkh@...nel.org>

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

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

ovl: fix null pointer dereference in ovl_permission()

Following process:
          P1                     P2
 path_lookupat
  link_path_walk
   inode_permission
    ovl_permission
      ovl_i_path_real(inode, &realpath)
        path->dentry = ovl_i_dentry_upper(inode)
                          drop_cache
			   __dentry_kill(ovl_dentry)
		            iput(ovl_inode)
		             ovl_destroy_inode(ovl_inode)
		              dput(oi->__upperdentry)
		               dentry_kill(upperdentry)
		                dentry_unlink_inode
				 upperdentry->d_inode = NULL
      realinode = d_inode(realpath.dentry) // return NULL
      inode_permission(realinode)
       inode->i_sb  // NULL pointer dereference
, will trigger an null pointer dereference at realinode:
  [  335.664979] BUG: kernel NULL pointer dereference,
                 address: 0000000000000002
  [  335.668032] CPU: 0 PID: 2592 Comm: ls Not tainted 6.3.0
  [  335.669956] RIP: 0010:inode_permission+0x33/0x2c0
  [  335.678939] Call Trace:
  [  335.679165]  <TASK>
  [  335.679371]  ovl_permission+0xde/0x320
  [  335.679723]  inode_permission+0x15e/0x2c0
  [  335.680090]  link_path_walk+0x115/0x550
  [  335.680771]  path_lookupat.isra.0+0xb2/0x200
  [  335.681170]  filename_lookup+0xda/0x240
  [  335.681922]  vfs_statx+0xa6/0x1f0
  [  335.682233]  vfs_fstatat+0x7b/0xb0

Fetch a reproducer in [Link].

Use the helper ovl_i_path_realinode() to get realinode and then do
non-nullptr checking.

The Linux kernel CVE team has assigned CVE-2023-53260 to this issue.


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

	Issue introduced in 5.19 with commit 4b7791b2e95805eaa9568761741d33cf929c930c and fixed in 6.1.43 with commit 53dd2ca2c02fdcfe3aad2345091d371063f97d17
	Issue introduced in 5.19 with commit 4b7791b2e95805eaa9568761741d33cf929c930c and fixed in 6.4.4 with commit 69f9ae7edf9ec0ff500429101923347fcba5c8c4
	Issue introduced in 5.19 with commit 4b7791b2e95805eaa9568761741d33cf929c930c and fixed in 6.5 with commit 1a73f5b8f079fd42a544c1600beface50c63af7c

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-2023-53260
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/overlayfs/inode.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/53dd2ca2c02fdcfe3aad2345091d371063f97d17
	https://git.kernel.org/stable/c/69f9ae7edf9ec0ff500429101923347fcba5c8c4
	https://git.kernel.org/stable/c/1a73f5b8f079fd42a544c1600beface50c63af7c