linux-cve-announce - CVE-2025-38218: f2fs: fix to do sanity check on sit_bitmap

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Message-ID: <2025070424-CVE-2025-38218-a5e8@gregkh>
Date: Fri,  4 Jul 2025 15:37:47 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38218: f2fs: fix to do sanity check on sit_bitmap_size

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

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

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

f2fs: fix to do sanity check on sit_bitmap_size

w/ below testcase, resize will generate a corrupted image which
contains inconsistent metadata, so when mounting such image, it
will trigger kernel panic:

touch img
truncate -s $((512*1024*1024*1024)) img
mkfs.f2fs -f img $((256*1024*1024))
resize.f2fs -s -i img -t $((1024*1024*1024))
mount img /mnt/f2fs

------------[ cut here ]------------
kernel BUG at fs/f2fs/segment.h:863!
Oops: invalid opcode: 0000 [#1] SMP PTI
CPU: 11 UID: 0 PID: 3922 Comm: mount Not tainted 6.15.0-rc1+ #191 PREEMPT(voluntary)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:f2fs_ra_meta_pages+0x47c/0x490

Call Trace:
 f2fs_build_segment_manager+0x11c3/0x2600
 f2fs_fill_super+0xe97/0x2840
 mount_bdev+0xf4/0x140
 legacy_get_tree+0x2b/0x50
 vfs_get_tree+0x29/0xd0
 path_mount+0x487/0xaf0
 __x64_sys_mount+0x116/0x150
 do_syscall_64+0x82/0x190
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7fdbfde1bcfe

The reaseon is:

sit_i->bitmap_size is 192, so size of sit bitmap is 192*8=1536, at maximum
there are 1536 sit blocks, however MAIN_SEGS is 261893, so that sit_blk_cnt
is 4762, build_sit_entries() -> current_sit_addr() tries to access
out-of-boundary in sit_bitmap at offset from [1536, 4762), once sit_bitmap
and sit_bitmap_mirror is not the same, it will trigger f2fs_bug_on().

Let's add sanity check in f2fs_sanity_check_ckpt() to avoid panic.

The Linux kernel CVE team has assigned CVE-2025-38218 to this issue.


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

	Fixed in 5.10.239 with commit 82f51bff393e4c12cf4de553120ca831cfa4ef19
	Fixed in 5.15.186 with commit 38ef48a8afef8df646b6f6ae7abb872f18b533c1
	Fixed in 6.1.142 with commit ad862f71016ba38039df1c96ed55c0a4314cc183
	Fixed in 6.6.95 with commit 79ef8a6c4ec53d327580fd7d2b522cf4f1d05b0c
	Fixed in 6.12.35 with commit ee1b421c469876544e297ec1090574bd76100247
	Fixed in 6.15.4 with commit 3e5ac62a56a24f4d88ce8ffd7bc452428b235868
	Fixed in 6.16-rc1 with commit 5db0d252c64e91ba1929c70112352e85dc5751e7

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-2025-38218
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/super.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/82f51bff393e4c12cf4de553120ca831cfa4ef19
	https://git.kernel.org/stable/c/38ef48a8afef8df646b6f6ae7abb872f18b533c1
	https://git.kernel.org/stable/c/ad862f71016ba38039df1c96ed55c0a4314cc183
	https://git.kernel.org/stable/c/79ef8a6c4ec53d327580fd7d2b522cf4f1d05b0c
	https://git.kernel.org/stable/c/ee1b421c469876544e297ec1090574bd76100247
	https://git.kernel.org/stable/c/3e5ac62a56a24f4d88ce8ffd7bc452428b235868
	https://git.kernel.org/stable/c/5db0d252c64e91ba1929c70112352e85dc5751e7