CVE-2026-43349: f2fs: fix to avoid uninit-value access in f2fs_sanity_check_node_footer

CVE-2026-43349: f2fs: fix to avoid uninit-value access in f2fs_sanity_check_node_footer

[Greg Kroah-Hartman]

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

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

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

f2fs: fix to avoid uninit-value access in f2fs_sanity_check_node_footer

syzbot reported a f2fs bug as below:

BUG: KMSAN: uninit-value in f2fs_sanity_check_node_footer+0x374/0xa20 fs/f2fs/node.c:1520
 f2fs_sanity_check_node_footer+0x374/0xa20 fs/f2fs/node.c:1520
 f2fs_finish_read_bio+0xe1e/0x1d60 fs/f2fs/data.c:177
 f2fs_read_end_io+0x6ab/0x2220 fs/f2fs/data.c:-1
 bio_endio+0x1006/0x1160 block/bio.c:1792
 submit_bio_noacct+0x533/0x2960 block/blk-core.c:891
 submit_bio+0x57a/0x620 block/blk-core.c:926
 blk_crypto_submit_bio include/linux/blk-crypto.h:203 [inline]
 f2fs_submit_read_bio+0x12c/0x360 fs/f2fs/data.c:557
 f2fs_submit_page_bio+0xee2/0x1450 fs/f2fs/data.c:775
 read_node_folio+0x384/0x4b0 fs/f2fs/node.c:1481
 __get_node_folio+0x5db/0x15d0 fs/f2fs/node.c:1576
 f2fs_get_inode_folio+0x40/0x50 fs/f2fs/node.c:1623
 do_read_inode fs/f2fs/inode.c:425 [inline]
 f2fs_iget+0x1209/0x9380 fs/f2fs/inode.c:596
 f2fs_fill_super+0x8f5a/0xb2e0 fs/f2fs/super.c:5184
 get_tree_bdev_flags+0x6e6/0x920 fs/super.c:1694
 get_tree_bdev+0x38/0x50 fs/super.c:1717
 f2fs_get_tree+0x35/0x40 fs/f2fs/super.c:5436
 vfs_get_tree+0xb3/0x5d0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3763 [inline]
 do_new_mount+0x885/0x1dd0 fs/namespace.c:3839
 path_mount+0x7a2/0x20b0 fs/namespace.c:4159
 do_mount fs/namespace.c:4172 [inline]
 __do_sys_mount fs/namespace.c:4361 [inline]
 __se_sys_mount+0x704/0x7f0 fs/namespace.c:4338
 __x64_sys_mount+0xe4/0x150 fs/namespace.c:4338
 x64_sys_call+0x39f0/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x134/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The root cause is: in f2fs_finish_read_bio(), we may access uninit data
in folio if we failed to read the data from device into folio, let's add
a check condition to avoid such issue.

The Linux kernel CVE team has assigned CVE-2026-43349 to this issue.


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

	Issue introduced in 6.18.13 with commit 855c54f1803e3ebc613677b4f389c7f92656a1fc and fixed in 6.18.25 with commit 59970b2586fef4b13e96527b9d232bed30b640cd
	Issue introduced in 7.0 with commit 50ac3ecd8e05b6bcc350c71a4307d40c030ec7e4 and fixed in 7.0.2 with commit a10b89343d41ceee1af0ec38d3a74e526c77fa09
	Issue introduced in 7.0 with commit 50ac3ecd8e05b6bcc350c71a4307d40c030ec7e4 and fixed in 7.1-rc1 with commit 7b9161a605e91d0987e2596a245dc1f21621b23f
	Issue introduced in 6.19.3 with commit c386753db52b3a80afa6612bfdcb925aa5ca260f

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-2026-43349
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/data.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/59970b2586fef4b13e96527b9d232bed30b640cd
	https://git.kernel.org/stable/c/a10b89343d41ceee1af0ec38d3a74e526c77fa09
	https://git.kernel.org/stable/c/7b9161a605e91d0987e2596a245dc1f21621b23f