CVE-2021-47256 mm/memory-failure: make sure wait for page writeback in memory_failure

2024-05-2114:19:50

Linux

www.cve.org

linux kernel

vulnerability

memory_failure

clear_inode

bug fix

page writeback

memory_failure

inode

kernel panic

crash dump

memory_failure

clear_inode

wait_on_page_writeback

fix

cve-2021-47256

6.2 Medium

AI Score

Confidence

Low

0.0004 Low

EPSS

Percentile

10.4%

JSON

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

mm/memory-failure: make sure wait for page writeback in memory_failure

Our syzkaller trigger the “BUG_ON(!list_empty(&inode->i_wb_list))” in
clear_inode:

kernel BUG at fs/inode.c:519!
Internal error: Oops - BUG: 0 [#1] SMP
Modules linked in:
Process syz-executor.0 (pid: 249, stack limit = 0x00000000a12409d7)
CPU: 1 PID: 249 Comm: syz-executor.0 Not tainted 4.19.95
Hardware name: linux,dummy-virt (DT)
pstate: 80000005 (Nzcv daif -PAN -UAO)
pc : clear_inode+0x280/0x2a8
lr : clear_inode+0x280/0x2a8
Call trace:
clear_inode+0x280/0x2a8
ext4_clear_inode+0x38/0xe8
ext4_free_inode+0x130/0xc68
ext4_evict_inode+0xb20/0xcb8
evict+0x1a8/0x3c0
iput+0x344/0x460
do_unlinkat+0x260/0x410
__arm64_sys_unlinkat+0x6c/0xc0
el0_svc_common+0xdc/0x3b0
el0_svc_handler+0xf8/0x160
el0_svc+0x10/0x218
Kernel panic - not syncing: Fatal exception

A crash dump of this problem show that someone called __munlock_pagevec
to clear page LRU without lock_page: do_mmap -> mmap_region -> do_munmap
-> munlock_vma_pages_range -> __munlock_pagevec.

As a result memory_failure will call identify_page_state without
wait_on_page_writeback. And after truncate_error_page clear the mapping
of this page. end_page_writeback won’t call sb_clear_inode_writeback to
clear inode->i_wb_list. That will trigger BUG_ON in clear_inode!

Fix it by checking PageWriteback too to help determine should we skip
wait_on_page_writeback.

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "mm/memory-failure.c"
    ],
    "versions": [
      {
        "version": "0bc1f8b0682c",
        "lessThan": "d05267fd27a5",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "0bc1f8b0682c",
        "lessThan": "6d210d547adc",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "0bc1f8b0682c",
        "lessThan": "566345aaabac",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "0bc1f8b0682c",
        "lessThan": "9e379da727a7",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "0bc1f8b0682c",
        "lessThan": "28788dc5c705",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "0bc1f8b0682c",
        "lessThan": "e8675d291ac0",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "mm/memory-failure.c"
    ],
    "versions": [
      {
        "version": "3.16",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "3.16",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "4.14.238",
        "lessThanOrEqual": "4.14.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "4.19.196",
        "lessThanOrEqual": "4.19.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.4.128",
        "lessThanOrEqual": "5.4.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.10.46",
        "lessThanOrEqual": "5.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.12.13",
        "lessThanOrEqual": "5.12.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.13",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]