Subject: CVE-2024-26956: nilfs2: fix failure to detect DAT corruption in btree and direct mappings

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

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

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

nilfs2: fix failure to detect DAT corruption in btree and direct mappings

Patch series "nilfs2: fix kernel bug at submit_bh_wbc()".

This resolves a kernel BUG reported by syzbot.  Since there are two
flaws involved, I've made each one a separate patch.

The first patch alone resolves the syzbot-reported bug, but I think
both fixes should be sent to stable, so I've tagged them as such.

This patch (of 2):

Syzbot has reported a kernel bug in submit_bh_wbc() when writing file data
to a nilfs2 file system whose metadata is corrupted.

There are two flaws involved in this issue.

The first flaw is that when nilfs_get_block() locates a data block using
btree or direct mapping, if the disk address translation routine
nilfs_dat_translate() fails with internal code -ENOENT due to DAT metadata
corruption, it can be passed back to nilfs_get_block().  This causes
nilfs_get_block() to misidentify an existing block as non-existent,
causing both data block lookup and insertion to fail inconsistently.

The second flaw is that nilfs_get_block() returns a successful status in
this inconsistent state.  This causes the caller __block_write_begin_int()
or others to request a read even though the buffer is not mapped,
resulting in a BUG_ON check for the BH_Mapped flag in submit_bh_wbc()
failing.

This fixes the first issue by changing the return value to code -EINVAL
when a conversion using DAT fails with code -ENOENT, avoiding the
conflicting condition that leads to the kernel bug described above.  Here,
code -EINVAL indicates that metadata corruption was detected during the
block lookup, which will be properly handled as a file system error and
converted to -EIO when passing through the nilfs2 bmap layer.

The Linux kernel CVE team has assigned CVE-2024-26956 to this issue.

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

	Issue introduced in 2.6.31 with commit c3a7abf06ce7 and fixed in 4.19.312 with commit b67189690eb4
	Issue introduced in 2.6.31 with commit c3a7abf06ce7 and fixed in 5.4.274 with commit 9cbe1ad5f435
	Issue introduced in 2.6.31 with commit c3a7abf06ce7 and fixed in 5.10.215 with commit c3b5c5c31e72
	Issue introduced in 2.6.31 with commit c3a7abf06ce7 and fixed in 5.15.154 with commit 2e2619ff5d0d
	Issue introduced in 2.6.31 with commit c3a7abf06ce7 and fixed in 6.1.84 with commit 46b832e09d43
	Issue introduced in 2.6.31 with commit c3a7abf06ce7 and fixed in 6.6.24 with commit f69e81396aea
	Issue introduced in 2.6.31 with commit c3a7abf06ce7 and fixed in 6.7.12 with commit a8e4d098de1c
	Issue introduced in 2.6.31 with commit c3a7abf06ce7 and fixed in 6.8.3 with commit 82827ca21e7c
	Issue introduced in 2.6.31 with commit c3a7abf06ce7 and fixed in 6.9 with commit f2f26b4a84a0

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-2024-26956
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/nilfs2/btree.c
	fs/nilfs2/direct.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/b67189690eb4b7ecc84ae16fa1e880e0123eaa35
	https://git.kernel.org/stable/c/9cbe1ad5f4354f4df1445e5f4883983328cd6d8e
	https://git.kernel.org/stable/c/c3b5c5c31e723b568f83d8cafab8629d9d830ffb
	https://git.kernel.org/stable/c/2e2619ff5d0def4bb6c2037a32a6eaa28dd95c84
	https://git.kernel.org/stable/c/46b832e09d43b394ac0f6d9485d2b1a06593f0b7
	https://git.kernel.org/stable/c/f69e81396aea66304d214f175aa371f1b5578862
	https://git.kernel.org/stable/c/a8e4d098de1c0f4c5c1f2ed4633a860f0da6d713
	https://git.kernel.org/stable/c/82827ca21e7c8a91384c5baa656f78a5adfa4ab4
	https://git.kernel.org/stable/c/f2f26b4a84a0ef41791bd2d70861c8eac748f4ba