Subject: CVE-2024-43859: f2fs: fix to truncate preallocated blocks in f2fs_file_open()

From: Greg Kroah-Hartman <[email-masked]>

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

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

f2fs: fix to truncate preallocated blocks in f2fs_file_open()

chenyuwen reports a f2fs bug as below:

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000011
 fscrypt_set_bio_crypt_ctx+0x78/0x1e8
 f2fs_grab_read_bio+0x78/0x208
 f2fs_submit_page_read+0x44/0x154
 f2fs_get_read_data_page+0x288/0x5f4
 f2fs_get_lock_data_page+0x60/0x190
 truncate_partial_data_page+0x108/0x4fc
 f2fs_do_truncate_blocks+0x344/0x5f0
 f2fs_truncate_blocks+0x6c/0x134
 f2fs_truncate+0xd8/0x200
 f2fs_iget+0x20c/0x5ac
 do_garbage_collect+0x5d0/0xf6c
 f2fs_gc+0x22c/0x6a4
 f2fs_disable_checkpoint+0xc8/0x310
 f2fs_fill_super+0x14bc/0x1764
 mount_bdev+0x1b4/0x21c
 f2fs_mount+0x20/0x30
 legacy_get_tree+0x50/0xbc
 vfs_get_tree+0x5c/0x1b0
 do_new_mount+0x298/0x4cc
 path_mount+0x33c/0x5fc
 __arm64_sys_mount+0xcc/0x15c
 invoke_syscall+0x60/0x150
 el0_svc_common+0xb8/0xf8
 do_el0_svc+0x28/0xa0
 el0_svc+0x24/0x84
 el0t_64_sync_handler+0x88/0xec

It is because inode.i_crypt_info is not initialized during below path:
- mount
 - f2fs_fill_super
  - f2fs_disable_checkpoint
   - f2fs_gc
    - f2fs_iget
     - f2fs_truncate

So, let's relocate truncation of preallocated blocks to f2fs_file_open(),
after fscrypt_file_open().

The Linux kernel CVE team has assigned CVE-2024-43859 to this issue.

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

	Issue introduced in 5.17 with commit d4dd19ec1ea0 and fixed in 6.1.109 with commit 5f04969136db
	Issue introduced in 5.17 with commit d4dd19ec1ea0 and fixed in 6.6.44 with commit f44a25a8bfe0
	Issue introduced in 5.17 with commit d4dd19ec1ea0 and fixed in 6.10.3 with commit 3ba0ae885215
	Issue introduced in 5.17 with commit d4dd19ec1ea0 and fixed in 6.11 with commit 298b1e4182d6

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-2024-43859
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/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/5f04969136db674f133781626e0b692c5f2bf2f0
	https://git.kernel.org/stable/c/f44a25a8bfe0c15d33244539696cd9119cf44d18
	https://git.kernel.org/stable/c/3ba0ae885215b325605ff7ebf6de12ac2adf204d
	https://git.kernel.org/stable/c/298b1e4182d657c3e388adcc29477904e9600ed5