linux-cve-announce - CVE-2025-37739: f2fs: fix to avoid out-of-bounds access in f2fs_truncate_inode

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Message-ID: <2025050133-CVE-2025-37739-06bb@gregkh>
Date: Thu,  1 May 2025 14:56:45 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-37739: f2fs: fix to avoid out-of-bounds access in f2fs_truncate_inode_blocks()

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

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

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

f2fs: fix to avoid out-of-bounds access in f2fs_truncate_inode_blocks()

syzbot reports an UBSAN issue as below:

------------[ cut here ]------------
UBSAN: array-index-out-of-bounds in fs/f2fs/node.h:381:10
index 18446744073709550692 is out of range for type '__le32[5]' (aka 'unsigned int[5]')
CPU: 0 UID: 0 PID: 5318 Comm: syz.0.0 Not tainted 6.14.0-rc3-syzkaller-00060-g6537cfb395f3 #0
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 ubsan_epilogue lib/ubsan.c:231 [inline]
 __ubsan_handle_out_of_bounds+0x121/0x150 lib/ubsan.c:429
 get_nid fs/f2fs/node.h:381 [inline]
 f2fs_truncate_inode_blocks+0xa5e/0xf60 fs/f2fs/node.c:1181
 f2fs_do_truncate_blocks+0x782/0x1030 fs/f2fs/file.c:808
 f2fs_truncate_blocks+0x10d/0x300 fs/f2fs/file.c:836
 f2fs_truncate+0x417/0x720 fs/f2fs/file.c:886
 f2fs_file_write_iter+0x1bdb/0x2550 fs/f2fs/file.c:5093
 aio_write+0x56b/0x7c0 fs/aio.c:1633
 io_submit_one+0x8a7/0x18a0 fs/aio.c:2052
 __do_sys_io_submit fs/aio.c:2111 [inline]
 __se_sys_io_submit+0x171/0x2e0 fs/aio.c:2081
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f238798cde9

index 18446744073709550692 (decimal, unsigned long long)
= 0xfffffffffffffc64 (hexadecimal, unsigned long long)
= -924 (decimal, long long)

In f2fs_truncate_inode_blocks(), UBSAN detects that get_nid() tries to
access .i_nid[-924], it means both offset[0] and level should zero.

The possible case should be in f2fs_do_truncate_blocks(), we try to
truncate inode size to zero, however, dn.ofs_in_node is zero and
dn.node_page is not an inode page, so it fails to truncate inode page,
and then pass zeroed free_from to f2fs_truncate_inode_blocks(), result
in this issue.

	if (dn.ofs_in_node || IS_INODE(dn.node_page)) {
		f2fs_truncate_data_blocks_range(&dn, count);
		free_from += count;
	}

I guess the reason why dn.node_page is not an inode page could be: there
are multiple nat entries share the same node block address, once the node
block address was reused, f2fs_get_node_page() may load a non-inode block.

Let's add a sanity check for such condition to avoid out-of-bounds access
issue.

The Linux kernel CVE team has assigned CVE-2025-37739 to this issue.


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

	Fixed in 6.1.135 with commit 98dbf2af63de0b551082c9bc48333910e009b09f
	Fixed in 6.6.88 with commit 8b5e5aac44fee122947a269f9034c048e4c295de
	Fixed in 6.12.24 with commit ecc461331604b07cdbdb7360dbdf78471653264c
	Fixed in 6.13.12 with commit d7242fd7946d4cba0411effb6b5048ca55125747
	Fixed in 6.14.3 with commit 6ba8b41d0aa4b82f90f0c416cb53fcef9696525d
	Fixed in 6.15-rc1 with commit e6494977bd4a83862118a05f57a8df40256951c0

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-2025-37739
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/node.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/98dbf2af63de0b551082c9bc48333910e009b09f
	https://git.kernel.org/stable/c/8b5e5aac44fee122947a269f9034c048e4c295de
	https://git.kernel.org/stable/c/ecc461331604b07cdbdb7360dbdf78471653264c
	https://git.kernel.org/stable/c/d7242fd7946d4cba0411effb6b5048ca55125747
	https://git.kernel.org/stable/c/6ba8b41d0aa4b82f90f0c416cb53fcef9696525d
	https://git.kernel.org/stable/c/e6494977bd4a83862118a05f57a8df40256951c0