CVE-2024-46701 libfs: fix infinite directory reads for offset dir

2024-09-1306:27:29

Linux

www.cve.org

linux kernel

libfs

infinite directory reads

EPSS

Percentile

9.6%

JSON

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

libfs: fix infinite directory reads for offset dir

After we switch tmpfs dir operations from simple_dir_operations to
simple_offset_dir_operations, every rename happened will fill new dentry
to dest dir’s maple tree(&SHMEM_I(inode)->dir_offsets->mt) with a free
key starting with octx->newx_offset, and then set newx_offset equals to
free key + 1. This will lead to infinite readdir combine with rename
happened at the same time, which fail generic/736 in xfstests(detail show
as below).

create 5000 files(1 2 3…) under one dir
call readdir(man 3 readdir) once, and get one entry
rename(entry, “TEMPFILE”), then rename(“TEMPFILE”, entry)
loop 2~3, until readdir return nothing or we loop too many
times(tmpfs break test with the second condition)

We choose the same logic what commit 9b378f6ad48cf (“btrfs: fix infinite
directory reads”) to fix it, record the last_index when we open dir, and
do not emit the entry which index >= last_index. The file->private_data
now used in offset dir can use directly to do this, and we also update
the last_index when we llseek the dir file.

[brauner: only update last_index after seek when offset is zero like Jan suggested]

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "fs/libfs.c"
    ],
    "versions": [
      {
        "version": "a2e459555c5f",
        "lessThan": "308b4fc2403b",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "a2e459555c5f",
        "lessThan": "64a7ce76fb90",
        "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/libfs.c"
    ],
    "versions": [
      {
        "version": "6.6",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "6.6",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.10.7",
        "lessThanOrEqual": "6.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.11",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]