linux-cve-announce - CVE-2022-50009: f2fs: fix null-ptr-deref in f2fs_get_dnode_of

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Message-ID: <2025061831-CVE-2022-50009-214a@gregkh>
Date: Wed, 18 Jun 2025 13:01:14 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-50009: f2fs: fix null-ptr-deref in f2fs_get_dnode_of_data

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

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

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

f2fs: fix null-ptr-deref in f2fs_get_dnode_of_data

There is issue as follows when test f2fs atomic write:
F2FS-fs (loop0): Can't find valid F2FS filesystem in 2th superblock
F2FS-fs (loop0): invalid crc_offset: 0
F2FS-fs (loop0): f2fs_check_nid_range: out-of-range nid=1, run fsck to fix.
F2FS-fs (loop0): f2fs_check_nid_range: out-of-range nid=2, run fsck to fix.
==================================================================
BUG: KASAN: null-ptr-deref in f2fs_get_dnode_of_data+0xac/0x16d0
Read of size 8 at addr 0000000000000028 by task rep/1990

CPU: 4 PID: 1990 Comm: rep Not tainted 5.19.0-rc6-next-20220715 #266
Call Trace:
 <TASK>
 dump_stack_lvl+0x6e/0x91
 print_report.cold+0x49a/0x6bb
 kasan_report+0xa8/0x130
 f2fs_get_dnode_of_data+0xac/0x16d0
 f2fs_do_write_data_page+0x2a5/0x1030
 move_data_page+0x3c5/0xdf0
 do_garbage_collect+0x2015/0x36c0
 f2fs_gc+0x554/0x1d30
 f2fs_balance_fs+0x7f5/0xda0
 f2fs_write_single_data_page+0xb66/0xdc0
 f2fs_write_cache_pages+0x716/0x1420
 f2fs_write_data_pages+0x84f/0x9a0
 do_writepages+0x130/0x3a0
 filemap_fdatawrite_wbc+0x87/0xa0
 file_write_and_wait_range+0x157/0x1c0
 f2fs_do_sync_file+0x206/0x12d0
 f2fs_sync_file+0x99/0xc0
 vfs_fsync_range+0x75/0x140
 f2fs_file_write_iter+0xd7b/0x1850
 vfs_write+0x645/0x780
 ksys_write+0xf1/0x1e0
 do_syscall_64+0x3b/0x90
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

As 3db1de0e582c commit changed atomic write way which new a cow_inode for
atomic write file, and also mark cow_inode as FI_ATOMIC_FILE.
When f2fs_do_write_data_page write cow_inode will use cow_inode's cow_inode
which is NULL. Then will trigger null-ptr-deref.
To solve above issue, introduce FI_COW_FILE flag for COW inode.

Fiexes: 3db1de0e582c("f2fs: change the current atomic write way")

The Linux kernel CVE team has assigned CVE-2022-50009 to this issue.


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

	Fixed in 5.18.18 with commit 0f63e33eca6fa29a11c76fa31db5fe1cada5ad6e
	Fixed in 5.19.4 with commit 7000ad53ec1b17bd2fac76984b7b0c663755cbb7
	Fixed in 6.0 with commit 4a2c5b7994960fac29cf8a3f4e62855bae1b27d4

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-2022-50009
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/f2fs/f2fs.h
	fs/f2fs/file.c
	fs/f2fs/segment.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/0f63e33eca6fa29a11c76fa31db5fe1cada5ad6e
	https://git.kernel.org/stable/c/7000ad53ec1b17bd2fac76984b7b0c663755cbb7
	https://git.kernel.org/stable/c/4a2c5b7994960fac29cf8a3f4e62855bae1b27d4