Subject: CVE-2024-38599: jffs2: prevent xattr node from overflowing the eraseblock

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

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

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

jffs2: prevent xattr node from overflowing the eraseblock

Add a check to make sure that the requested xattr node size is no larger
than the eraseblock minus the cleanmarker.

Unlike the usual inode nodes, the xattr nodes aren't split into parts
and spread across multiple eraseblocks, which means that a xattr node
must not occupy more than one eraseblock. If the requested xattr value is
too large, the xattr node can spill onto the next eraseblock, overwriting
the nodes and causing errors such as:

jffs2: argh. node added in wrong place at 0x0000b050(2)
jffs2: nextblock 0x0000a000, expected at 0000b00c
jffs2: error: (823) do_verify_xattr_datum: node CRC failed at 0x01e050,
read=0xfc892c93, calc=0x000000
jffs2: notice: (823) jffs2_get_inode_nodes: Node header CRC failed
at 0x01e00c. {848f,2fc4,0fef511f,59a3d171}
jffs2: Node at 0x0000000c with length 0x00001044 would run over the
end of the erase block
jffs2: Perhaps the file system was created with the wrong erase size?
jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found
at 0x00000010: 0x1044 instead

This breaks the filesystem and can lead to KASAN crashes such as:

BUG: KASAN: slab-out-of-bounds in jffs2_sum_add_kvec+0x125e/0x15d0
Read of size 4 at addr ffff88802c31e914 by task repro/830
CPU: 0 PID: 830 Comm: repro Not tainted 6.9.0-rc3+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS Arch Linux 1.16.3-1-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xc6/0x120
 print_report+0xc4/0x620
 ? __virt_addr_valid+0x308/0x5b0
 kasan_report+0xc1/0xf0
 ? jffs2_sum_add_kvec+0x125e/0x15d0
 ? jffs2_sum_add_kvec+0x125e/0x15d0
 jffs2_sum_add_kvec+0x125e/0x15d0
 jffs2_flash_direct_writev+0xa8/0xd0
 jffs2_flash_writev+0x9c9/0xef0
 ? __x64_sys_setxattr+0xc4/0x160
 ? do_syscall_64+0x69/0x140
 ? entry_SYSCALL_64_after_hwframe+0x76/0x7e
 [...]

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

The Linux kernel CVE team has assigned CVE-2024-38599 to this issue.

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

	Issue introduced in 2.6.18 with commit aa98d7cf59b5 and fixed in 4.19.316 with commit 2904e1d9b64f
	Issue introduced in 2.6.18 with commit aa98d7cf59b5 and fixed in 5.4.278 with commit 526235dffcac
	Issue introduced in 2.6.18 with commit aa98d7cf59b5 and fixed in 5.10.219 with commit f0eea095ce8c
	Issue introduced in 2.6.18 with commit aa98d7cf59b5 and fixed in 5.15.161 with commit a1d21bcd78cf
	Issue introduced in 2.6.18 with commit aa98d7cf59b5 and fixed in 6.1.93 with commit f06969df2e40
	Issue introduced in 2.6.18 with commit aa98d7cf59b5 and fixed in 6.6.33 with commit af82d8d2179b
	Issue introduced in 2.6.18 with commit aa98d7cf59b5 and fixed in 6.8.12 with commit 8d431391320c
	Issue introduced in 2.6.18 with commit aa98d7cf59b5 and fixed in 6.9.3 with commit 978a12c91b38
	Issue introduced in 2.6.18 with commit aa98d7cf59b5 and fixed in 6.10 with commit c6854e5a267c

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-2024-38599
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/jffs2/xattr.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/2904e1d9b64f72d291095e3cbb31634f08788b11
	https://git.kernel.org/stable/c/526235dffcac74c7823ed504dfac4f88d84ba5df
	https://git.kernel.org/stable/c/f0eea095ce8c959b86e1e57fe36ca4fea5ae54f8
	https://git.kernel.org/stable/c/a1d21bcd78cf4a4353e1e835789429c6b76aca8b
	https://git.kernel.org/stable/c/f06969df2e40ab1dc8f4364a5de967830c74a098
	https://git.kernel.org/stable/c/af82d8d2179b7277ad627c39e7e0778f1c86ccdb
	https://git.kernel.org/stable/c/8d431391320c5c5398ff966fb3a95e68a7def275
	https://git.kernel.org/stable/c/978a12c91b38bf1a213e567f3c20e2beef215f07
	https://git.kernel.org/stable/c/c6854e5a267c28300ff045480b5a7ee7f6f1d913