CVE-2024-44941 f2fs: fix to cover read extent cache access with lock

2024-08-2611:20:45

Linux

www.cve.org

linux kernel

f2fs

vulnerability

fix

read extent cache

access

lock

kasan

bug

google compute engine

bios

cve-2024-44941

EPSS

Percentile

5.1%

JSON

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

f2fs: fix to cover read extent cache access with lock

syzbot reports a f2fs bug as below:

BUG: KASAN: slab-use-after-free in sanity_check_extent_cache+0x370/0x410 fs/f2fs/extent_cache.c:46
Read of size 4 at addr ffff8880739ab220 by task syz-executor200/5097

CPU: 0 PID: 5097 Comm: syz-executor200 Not tainted 6.9.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
print_address_description mm/kasan/report.c:377 [inline]
print_report+0x169/0x550 mm/kasan/report.c:488
kasan_report+0x143/0x180 mm/kasan/report.c:601
sanity_check_extent_cache+0x370/0x410 fs/f2fs/extent_cache.c:46
do_read_inode fs/f2fs/inode.c:509 [inline]
f2fs_iget+0x33e1/0x46e0 fs/f2fs/inode.c:560
f2fs_nfs_get_inode+0x74/0x100 fs/f2fs/super.c:3237
generic_fh_to_dentry+0x9f/0xf0 fs/libfs.c:1413
exportfs_decode_fh_raw+0x152/0x5f0 fs/exportfs/expfs.c:444
exportfs_decode_fh+0x3c/0x80 fs/exportfs/expfs.c:584
do_handle_to_path fs/fhandle.c:155 [inline]
handle_to_path fs/fhandle.c:210 [inline]
do_handle_open+0x495/0x650 fs/fhandle.c:226
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

We missed to cover sanity_check_extent_cache() w/ extent cache lock,
so, below race case may happen, result in use after free issue.

f2fs_iget
do_read_inode
f2fs_init_read_extent_tree
: add largest extent entry in to cache
- shrink
- f2fs_shrink_read_extent_tree
- __shrink_extent_tree
- __detach_extent_node
: drop largest extent entry
sanity_check_extent_cache
: access et->largest w/o lock

let’s refactor sanity_check_extent_cache() to avoid extent cache access
and call it before f2fs_init_read_extent_tree() to fix this issue.

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "fs/f2fs/extent_cache.c",
      "fs/f2fs/f2fs.h",
      "fs/f2fs/inode.c"
    ],
    "versions": [
      {
        "version": "1da177e4c3f4",
        "lessThan": "263df78166d3",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1da177e4c3f4",
        "lessThan": "323ef20b5558",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1da177e4c3f4",
        "lessThan": "d7409b05a64f",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "fs/f2fs/extent_cache.c",
      "fs/f2fs/f2fs.h",
      "fs/f2fs/inode.c"
    ],
    "versions": [
      {
        "version": "6.6.47",
        "lessThanOrEqual": "6.6.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.10.6",
        "lessThanOrEqual": "6.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.11",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]