Subject: CVE-2024-44939: jfs: fix null ptr deref in dtInsertEntry

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

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

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

jfs: fix null ptr deref in dtInsertEntry

[syzbot reported]
general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 0 PID: 5061 Comm: syz-executor404 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
RIP: 0010:dtInsertEntry+0xd0c/0x1780 fs/jfs/jfs_dtree.c:3713
...
[Analyze]
In dtInsertEntry(), when the pointer h has the same value as p, after writing
name in UniStrncpy_to_le(), p->header.flag will be cleared. This will cause the
previously true judgment "p->header.flag & BT-LEAF" to change to no after writing
the name operation, this leads to entering an incorrect branch and accessing the
uninitialized object ih when judging this condition for the second time.

[Fix]
After got the page, check freelist first, if freelist == 0 then exit dtInsert()
and return -EINVAL.

The Linux kernel CVE team has assigned CVE-2024-44939 to this issue.

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

	Fixed in 6.1.107 with commit 53023ab11836
	Fixed in 6.6.47 with commit 6ea10dbb1e6c
	Fixed in 6.10.6 with commit 9c2ac38530d1
	Fixed in 6.11 with commit ce6dede912f0

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-2024-44939
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/jfs/jfs_dtree.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/53023ab11836ac56fd75f7a71ec1356e50920fa9
	https://git.kernel.org/stable/c/6ea10dbb1e6c58384136e9adfd75f81951e423f6
	https://git.kernel.org/stable/c/9c2ac38530d1a3ee558834dfa16c85a40fd0e702
	https://git.kernel.org/stable/c/ce6dede912f064a855acf6f04a04cbb2c25b8c8c