CVE-2021-47507 nfsd: Fix nsfd startup race (again)

2024-05-2415:01:53

Linux

www.cve.org

linux kernel

vulnerability

nfsd

race

crash

null pointer

dereference

rpc

pipefs

event

fix

regression

6.3 Medium

AI Score

Confidence

High

0.0004 Low

EPSS

Percentile

15.5%

JSON

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

nfsd: Fix nsfd startup race (again)

Commit bd5ae9288d64 (“nfsd: register pernet ops last, unregister first”)
has re-opened rpc_pipefs_event() race against nfsd_net_id registration
(register_pernet_subsys()) which has been fixed by commit bb7ffbf29e76
(“nfsd: fix nsfd startup race triggering BUG_ON”).

Restore the order of register_pernet_subsys() vs register_cld_notifier().
Add WARN_ON() to prevent a future regression.

Crash info:
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000012
CPU: 8 PID: 345 Comm: mount Not tainted 5.4.144-… #1
pc : rpc_pipefs_event+0x54/0x120 [nfsd]
lr : rpc_pipefs_event+0x48/0x120 [nfsd]
Call trace:
rpc_pipefs_event+0x54/0x120 [nfsd]
blocking_notifier_call_chain
rpc_fill_super
get_tree_keyed
rpc_fs_get_tree
vfs_get_tree
do_mount
ksys_mount
__arm64_sys_mount
el0_svc_handler
el0_svc

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "fs/nfsd/nfs4recover.c",
      "fs/nfsd/nfsctl.c"
    ],
    "versions": [
      {
        "version": "8677e99150b0",
        "lessThan": "f5734b1714ca",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "7c7cb07d4aff",
        "lessThan": "c520943a00ad",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "bd5ae9288d64",
        "lessThan": "8bf902fee589",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "bd5ae9288d64",
        "lessThan": "b10252c7ae9c",
        "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/nfsd/nfs4recover.c",
      "fs/nfsd/nfsctl.c"
    ],
    "versions": [
      {
        "version": "5.12",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "5.12",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.4.165",
        "lessThanOrEqual": "5.4.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.10.85",
        "lessThanOrEqual": "5.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.15.8",
        "lessThanOrEqual": "5.15.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.16",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]