hfsplus: don't query the device logical block size multiple times
CVE: CVE-2024-56548
Component: kernel
CWE: CWE-787
Severity: Moderate
CVSS v3: 7.4/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Release date: 2024-12-27T00:00:00+00:00

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

hfsplus: don't query the device logical block size multiple times

Devices block sizes may change. One of these cases is a loop device by
using ioctl LOOP_SET_BLOCK_SIZE.

While this may cause other issues like IO being rejected, in the case of
hfsplus, it will allocate a block by using that size and potentially write
out-of-bounds when hfsplus_read_wrapper calls hfsplus_submit_bio and the
latter function reads a different io_size.

Using a new min_io_size initally set to sb_min_blocksize works for the
purposes of the original fix, since it will be set to the max between
HFSPLUS_SECTOR_SIZE and the first seen logical block size. We still use the
max between HFSPLUS_SECTOR_SIZE and min_io_size in case the latter is not
initialized.

Tested by mounting an hfsplus filesystem with loop block sizes 512, 1024
and 4096.

The produced KASAN report before the fix looks like this:

[  419.944641] ==================================================================
[  419.945655] BUG: KASAN: slab-use-after-free in hfsplus_read_wrapper+0x659/0xa0a
[  419.946703] Read of size 2 at addr ffff88800721fc00 by task repro/10678
[  419.947612]
[  419.947846] CPU: 0 UID: 0 PID: 10678 Comm: repro Not tainted 6.12.0-rc5-00008-gdf56e0f2f3ca #84
[  419.949007] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014
[  419.950035] Call Trace:
[  419.950384]  <TASK>
[  419.950676]  dump_stack_lvl+0x57/0x78
[  419.951212]  ? hfsplus_read_wrapper+0x659/0xa0a
[  419.951830]  print_report+0x14c/0x49e
[  419.952361]  ? __virt_addr_valid+0x267/0x278
[  419.952979]  ? kmem_cache_debug_flags+0xc/0x1d
[  419.953561]  ? hfsplus_read_wrapper+0x659/0xa0a
[  419.954231]  kasan_report+0x89/0xb0
[  419.954748]  ? hfsplus_read_wrapper+0x659/0xa0a
[  419.955367]  hfsplus_read_wrapper+0x659/0xa0a
[  419.955948]  ? __pfx_hfsplus_read_wrapper+0x10/0x10
[  419.956618]  ? do_raw_spin_unlock+0x59/0x1a9
[  419.957214]  ? _raw_spin_unlock+0x1a/0x2e
[  419.957772]  hfsplus_fill_super+0x348/0x1590
[  419.958355]  ? hlock_class+0x4c/0x109
[  419.958867]  ? __pfx_hfsplus_fill_super+0x10/0x10
[  419.959499]  ? __pfx_string+0x10/0x10
[  419.960006]  ? lock_acquire+0x3e2/0x454
[  419.960532]  ? bdev_name.constprop.0+0xce/0x243
[  419.961129]  ? __pfx_bdev_name.constprop.0+0x10/0x10
[  419.961799]  ? pointer+0x3f0/0x62f
[  419.962277]  ? __pfx_pointer+0x10/0x10
[  419.962761]  ? vsnprintf+0x6c4/0xfba
[  419.963178]  ? __pfx_vsnprintf+0x10/0x10
[  419.963621]  ? setup_bdev_super+0x376/0x3b3
[  419.964029]  ? snprintf+0x9d/0xd2
[  419.964344]  ? __pfx_snprintf+0x10/0x10
[  419.964675]  ? lock_acquired+0x45c/0x5e9
[  419.965016]  ? set_blocksize+0x139/0x1c1
[  419.965381]  ? sb_set_blocksize+0x6d/0xae
[  419.965742]  ? __pfx_hfsplus_fill_super+0x10/0x10
[  419.966179]  mount_bdev+0x12f/0x1bf
[  419.966512]  ? __pfx_mount_bdev+0x10/0x10
[  419.966886]  ? vfs_parse_fs_string+0xce/0x111
[  419.967293]  ? __pfx_vfs_parse_fs_string+0x10/0x10
[  419.967702]  ? __pfx_hfsplus_mount+0x10/0x10
[  419.968073]  legacy_get_tree+0x104/0x178
[  419.968414]  vfs_get_tree+0x86/0x296
[  419.968751]  path_mount+0xba3/0xd0b
[  419.969157]  ? __pfx_path_mount+0x10/0x10
[  419.969594]  ? kmem_cache_free+0x1e2/0x260
[  419.970311]  do_mount+0x99/0xe0
[  419.970630]  ? __pfx_do_mount+0x10/0x10
[  419.971008]  __do_sys_mount+0x199/0x1c9
[  419.971397]  do_syscall_64+0xd0/0x135
[  419.971761]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[  419.972233] RIP: 0033:0x7c3cb812972e
[  419.972564] Code: 48 8b 0d f5 46 0d 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d c2 46 0d 00 f7 d8 64 89 01 48
[  419.974371] RSP: 002b:00007ffe30632548 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
[  419.975048] RAX: ffffffffffffffda RBX: 00007ffe306328d8 RCX: 00007c3cb812972e
[  419.975701] RDX: 0000000020000000 RSI: 0000000020000c80 RDI:
---truncated---


Remediation: