linux-cve-announce - CVE-2021-47638: ubifs: rename_whiteout: Fix double free for whiteout

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Message-ID: <2025022647-CVE-2021-47638-5ede@gregkh>
Date: Wed, 26 Feb 2025 02:53:49 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2021-47638: ubifs: rename_whiteout: Fix double free for whiteout_ui->data

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

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

ubifs: rename_whiteout: Fix double free for whiteout_ui->data

'whiteout_ui->data' will be freed twice if space budget fail for
rename whiteout operation as following process:

rename_whiteout
  dev = kmalloc
  whiteout_ui->data = dev
  kfree(whiteout_ui->data)  // Free first time
  iput(whiteout)
    ubifs_free_inode
      kfree(ui->data)	    // Double free!

KASAN reports:
==================================================================
BUG: KASAN: double-free or invalid-free in ubifs_free_inode+0x4f/0x70
Call Trace:
  kfree+0x117/0x490
  ubifs_free_inode+0x4f/0x70 [ubifs]
  i_callback+0x30/0x60
  rcu_do_batch+0x366/0xac0
  __do_softirq+0x133/0x57f

Allocated by task 1506:
  kmem_cache_alloc_trace+0x3c2/0x7a0
  do_rename+0x9b7/0x1150 [ubifs]
  ubifs_rename+0x106/0x1f0 [ubifs]
  do_syscall_64+0x35/0x80

Freed by task 1506:
  kfree+0x117/0x490
  do_rename.cold+0x53/0x8a [ubifs]
  ubifs_rename+0x106/0x1f0 [ubifs]
  do_syscall_64+0x35/0x80

The buggy address belongs to the object at ffff88810238bed8 which
belongs to the cache kmalloc-8 of size 8
==================================================================

Let ubifs_free_inode() free 'whiteout_ui->data'. BTW, delete unused
assignment 'whiteout_ui->data_len = 0', process 'ubifs_evict_inode()
-> ubifs_jnl_delete_inode() -> ubifs_jnl_write_inode()' doesn't need it
(because 'inc_nlink(whiteout)' won't be excuted by 'goto out_release',
 and the nlink of whiteout inode is 0).

The Linux kernel CVE team has assigned CVE-2021-47638 to this issue.


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

	Issue introduced in 4.9 with commit 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and fixed in 4.14.276 with commit 8b3c7be16f3f4dfd6e15ac651484e59d3fa36274
	Issue introduced in 4.9 with commit 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and fixed in 4.19.238 with commit 2b3236ecf96db7af5836e1366ce39ace8ce832fa
	Issue introduced in 4.9 with commit 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and fixed in 5.4.189 with commit 14276d38c89a170363e90b6ac0a53c3cf61b87fc
	Issue introduced in 4.9 with commit 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and fixed in 5.10.110 with commit a90e2dbe66d2647ff95a0442ad2e86482d977fd8
	Issue introduced in 4.9 with commit 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and fixed in 5.15.33 with commit 2ad07009c459e56ebdcc089d850d664660fdb742
	Issue introduced in 4.9 with commit 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and fixed in 5.16.19 with commit b9a937f096e608b3368c1abc920d4d640ba2c94f
	Issue introduced in 4.9 with commit 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and fixed in 5.17.2 with commit 6d7a158a7363c1f6604aa47ae1a280a5c65123dd
	Issue introduced in 4.9 with commit 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and fixed in 5.18 with commit 40a8f0d5e7b3999f096570edab71c345da812e3e

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-2021-47638
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/ubifs/dir.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/8b3c7be16f3f4dfd6e15ac651484e59d3fa36274
	https://git.kernel.org/stable/c/2b3236ecf96db7af5836e1366ce39ace8ce832fa
	https://git.kernel.org/stable/c/14276d38c89a170363e90b6ac0a53c3cf61b87fc
	https://git.kernel.org/stable/c/a90e2dbe66d2647ff95a0442ad2e86482d977fd8
	https://git.kernel.org/stable/c/2ad07009c459e56ebdcc089d850d664660fdb742
	https://git.kernel.org/stable/c/b9a937f096e608b3368c1abc920d4d640ba2c94f
	https://git.kernel.org/stable/c/6d7a158a7363c1f6604aa47ae1a280a5c65123dd
	https://git.kernel.org/stable/c/40a8f0d5e7b3999f096570edab71c345da812e3e