hfsplus: fix KMSAN uninit-value issue in __hfsplus_ext_cache_extent()
CVE: CVE-2025-40244
Component: kernel
CWE: CWE-665
Severity: Moderate
CVSS v3: 4.7/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Release date: 2025-12-04T00:00:00+00:00

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

hfsplus: fix KMSAN uninit-value issue in __hfsplus_ext_cache_extent()

The syzbot reported issue in __hfsplus_ext_cache_extent():

[   70.194323][ T9350] BUG: KMSAN: uninit-value in __hfsplus_ext_cache_extent+0x7d0/0x990
[   70.195022][ T9350]  __hfsplus_ext_cache_extent+0x7d0/0x990
[   70.195530][ T9350]  hfsplus_file_extend+0x74f/0x1cf0
[   70.195998][ T9350]  hfsplus_get_block+0xe16/0x17b0
[   70.196458][ T9350]  __block_write_begin_int+0x962/0x2ce0
[   70.196959][ T9350]  cont_write_begin+0x1000/0x1950
[   70.197416][ T9350]  hfsplus_write_begin+0x85/0x130
[   70.197873][ T9350]  generic_perform_write+0x3e8/0x1060
[   70.198374][ T9350]  __generic_file_write_iter+0x215/0x460
[   70.198892][ T9350]  generic_file_write_iter+0x109/0x5e0
[   70.199393][ T9350]  vfs_write+0xb0f/0x14e0
[   70.199771][ T9350]  ksys_write+0x23e/0x490
[   70.200149][ T9350]  __x64_sys_write+0x97/0xf0
[   70.200570][ T9350]  x64_sys_call+0x3015/0x3cf0
[   70.201065][ T9350]  do_syscall_64+0xd9/0x1d0
[   70.201506][ T9350]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
[   70.202054][ T9350]
[   70.202279][ T9350] Uninit was created at:
[   70.202693][ T9350]  __kmalloc_noprof+0x621/0xf80
[   70.203149][ T9350]  hfsplus_find_init+0x8d/0x1d0
[   70.203602][ T9350]  hfsplus_file_extend+0x6ca/0x1cf0
[   70.204087][ T9350]  hfsplus_get_block+0xe16/0x17b0
[   70.204561][ T9350]  __block_write_begin_int+0x962/0x2ce0
[   70.205074][ T9350]  cont_write_begin+0x1000/0x1950
[   70.205547][ T9350]  hfsplus_write_begin+0x85/0x130
[   70.206017][ T9350]  generic_perform_write+0x3e8/0x1060
[   70.206519][ T9350]  __generic_file_write_iter+0x215/0x460
[   70.207042][ T9350]  generic_file_write_iter+0x109/0x5e0
[   70.207552][ T9350]  vfs_write+0xb0f/0x14e0
[   70.207961][ T9350]  ksys_write+0x23e/0x490
[   70.208375][ T9350]  __x64_sys_write+0x97/0xf0
[   70.208810][ T9350]  x64_sys_call+0x3015/0x3cf0
[   70.209255][ T9350]  do_syscall_64+0xd9/0x1d0
[   70.209680][ T9350]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
[   70.210230][ T9350]
[   70.210454][ T9350] CPU: 2 UID: 0 PID: 9350 Comm: repro Not tainted 6.12.0-rc5 #5
[   70.211174][ T9350] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[   70.212115][ T9350] =====================================================
[   70.212734][ T9350] Disabling lock debugging due to kernel taint
[   70.213284][ T9350] Kernel panic - not syncing: kmsan.panic set ...
[   70.213858][ T9350] CPU: 2 UID: 0 PID: 9350 Comm: repro Tainted: G    B              6.12.0-rc5 #5
[   70.214679][ T9350] Tainted: [B]=BAD_PAGE
[   70.215057][ T9350] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[   70.215999][ T9350] Call Trace:
[   70.216309][ T9350]  <TASK>
[   70.216585][ T9350]  dump_stack_lvl+0x1fd/0x2b0
[   70.217025][ T9350]  dump_stack+0x1e/0x30
[   70.217421][ T9350]  panic+0x502/0xca0
[   70.217803][ T9350]  ? kmsan_get_metadata+0x13e/0x1c0

[   70.218294][ Message fromT sy9350]  kmsan_report+0x296/slogd@syzkaller 0x2aat Aug 18 22:11:058 ...
 kernel
:[   70.213284][ T9350] Kernel panic - not syncing: kmsan.panic [   70.220179][ T9350]  ? kmsan_get_metadata+0x13e/0x1c0
set ...
[   70.221254][ T9350]  ? __msan_warning+0x96/0x120
[   70.222066][ T9350]  ? __hfsplus_ext_cache_extent+0x7d0/0x990
[   70.223023][ T9350]  ? hfsplus_file_extend+0x74f/0x1cf0
[   70.224120][ T9350]  ? hfsplus_get_block+0xe16/0x17b0
[   70.224946][ T9350]  ? __block_write_begin_int+0x962/0x2ce0
[   70.225756][ T9350]  ? cont_write_begin+0x1000/0x1950
[   70.226337][ T9350]  ? hfsplus_write_begin+0x85/0x130
[   70.226852][ T9350]  ? generic_perform_write+0x3e8/0x1060
[   70.227405][ T9350]  ? __generic_file_write_iter+0x215/0x460
[   70.227979][ T9350]  ? generic_file_write_iter+0x109/0x5e0
[   70.228540][ T9350]  ? vfs_write+0xb0f/0x14e0
[   70.228997][ T9350]  ? ksys_write+0x23e/0x490
---truncated---


Remediation:
Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.