linux-cve-announce - CVE-2024-42297: f2fs: fix to don't dirty inode for readonly filesystem

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Message-ID: <2024081747-CVE-2024-42297-fcec@gregkh>
Date: Sat, 17 Aug 2024 11:10:02 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-42297: f2fs: fix to don't dirty inode for readonly filesystem

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

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

f2fs: fix to don't dirty inode for readonly filesystem

syzbot reports f2fs bug as below:

kernel BUG at fs/f2fs/inode.c:933!
RIP: 0010:f2fs_evict_inode+0x1576/0x1590 fs/f2fs/inode.c:933
Call Trace:
 evict+0x2a4/0x620 fs/inode.c:664
 dispose_list fs/inode.c:697 [inline]
 evict_inodes+0x5f8/0x690 fs/inode.c:747
 generic_shutdown_super+0x9d/0x2c0 fs/super.c:675
 kill_block_super+0x44/0x90 fs/super.c:1667
 kill_f2fs_super+0x303/0x3b0 fs/f2fs/super.c:4894
 deactivate_locked_super+0xc1/0x130 fs/super.c:484
 cleanup_mnt+0x426/0x4c0 fs/namespace.c:1256
 task_work_run+0x24a/0x300 kernel/task_work.c:180
 ptrace_notify+0x2cd/0x380 kernel/signal.c:2399
 ptrace_report_syscall include/linux/ptrace.h:411 [inline]
 ptrace_report_syscall_exit include/linux/ptrace.h:473 [inline]
 syscall_exit_work kernel/entry/common.c:251 [inline]
 syscall_exit_to_user_mode_prepare kernel/entry/common.c:278 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
 syscall_exit_to_user_mode+0x15c/0x280 kernel/entry/common.c:296
 do_syscall_64+0x50/0x110 arch/x86/entry/common.c:88
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

The root cause is:
- do_sys_open
 - f2fs_lookup
  - __f2fs_find_entry
   - f2fs_i_depth_write
    - f2fs_mark_inode_dirty_sync
     - f2fs_dirty_inode
      - set_inode_flag(inode, FI_DIRTY_INODE)

- umount
 - kill_f2fs_super
  - kill_block_super
   - generic_shutdown_super
    - sync_filesystem
    : sb is readonly, skip sync_filesystem()
    - evict_inodes
     - iput
      - f2fs_evict_inode
       - f2fs_bug_on(sbi, is_inode_flag_set(inode, FI_DIRTY_INODE))
       : trigger kernel panic

When we try to repair i_current_depth in readonly filesystem, let's
skip dirty inode to avoid panic in later f2fs_evict_inode().

The Linux kernel CVE team has assigned CVE-2024-42297 to this issue.

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

	Fixed in 6.1.103 with commit 9ce8135accf1
	Fixed in 6.6.44 with commit e62ff092a42f
	Fixed in 6.10.3 with commit 2434344559f6
	Fixed in 6.11-rc1 with commit 192b8fb8d1c8

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-2024-42297
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/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/9ce8135accf103f7333af472709125878704fdd4
	https://git.kernel.org/stable/c/e62ff092a42f4a1bae3b310cf46673b4f3aac3b5
	https://git.kernel.org/stable/c/2434344559f6743efb3ac15d11af9a0db9543bd3
	https://git.kernel.org/stable/c/192b8fb8d1c8ca3c87366ebbef599fa80bb626b8