CVE-2024-39276

2024-06-2515:15:13

416baaa9-dc9f-4396-8d5f-8c081fb06d67

web.nvd.nist.gov

linux kernel

e_refcnt leak

mb_cache_entry

ext4_xattr_block_cache_find

syzbot

warning

cpu

pid

fs/mbcache.c

ext4_put_super

generic_shutdown_super

kill_block_super

ext4_kill_sb

-enomem

mb_cache_destroy

6.9 Medium

AI Score

Confidence

Low

0.0004 Low

EPSS

Percentile

13.2%

JSON

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

ext4: fix mb_cache_entry’s e_refcnt leak in ext4_xattr_block_cache_find()

Syzbot reports a warning as follows:

============================================
WARNING: CPU: 0 PID: 5075 at fs/mbcache.c:419 mb_cache_destroy+0x224/0x290
Modules linked in:
CPU: 0 PID: 5075 Comm: syz-executor199 Not tainted 6.9.0-rc6-gb947cc5bf6d7
RIP: 0010:mb_cache_destroy+0x224/0x290 fs/mbcache.c:419
Call Trace:
<TASK>
ext4_put_super+0x6d4/0xcd0 fs/ext4/super.c:1375
generic_shutdown_super+0x136/0x2d0 fs/super.c:641
kill_block_super+0x44/0x90 fs/super.c:1675
ext4_kill_sb+0x68/0xa0 fs/ext4/super.c:7327
[…]

This is because when finding an entry in ext4_xattr_block_cache_find(), if
ext4_sb_bread() returns -ENOMEM, the ce’s e_refcnt, which has already grown
in the __entry_find(), won’t be put away, and eventually trigger the above
issue in mb_cache_destroy() due to reference count leakage.

So call mb_cache_entry_put() on the -ENOMEM error branch as a quick fix.

Affected configurations

Vulners

Node

linuxlinux_kernelRange5.0–4.19.316

linuxlinux_kernelRange4.20.0–5.4.278

linuxlinux_kernelRange5.5.0–5.10.219

linuxlinux_kernelRange5.11.0–5.15.161

linuxlinux_kernelRange5.16.0–6.1.94

linuxlinux_kernelRange6.2.0–6.6.34

linuxlinux_kernelRange6.7.0–6.9.5

linuxlinux_kernelRange6.10.0–6.10-rc1

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "fs/ext4/xattr.c"
    ],
    "versions": [
      {
        "version": "b878c8a7f08f",
        "lessThan": "9ad75e78747b",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "fb265c9cb49e",
        "lessThan": "896a7e7d0d55",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "fb265c9cb49e",
        "lessThan": "76dc776153a4",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "fb265c9cb49e",
        "lessThan": "681ff9a09acc",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "fb265c9cb49e",
        "lessThan": "e941b712e758",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "fb265c9cb49e",
        "lessThan": "a95df6f04f2c",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "fb265c9cb49e",
        "lessThan": "b37c0edef4e6",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "fb265c9cb49e",
        "lessThan": "0c0b4a49d3e7",
        "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/ext4/xattr.c"
    ],
    "versions": [
      {
        "version": "5.0",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "5.0",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "4.19.316",
        "lessThanOrEqual": "4.19.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.4.278",
        "lessThanOrEqual": "5.4.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.10.219",
        "lessThanOrEqual": "5.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.15.161",
        "lessThanOrEqual": "5.15.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.1.94",
        "lessThanOrEqual": "6.1.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.6.34",
        "lessThanOrEqual": "6.6.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.9.5",
        "lessThanOrEqual": "6.9.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.10-rc1",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]