CVE-2024-46695 selinux,smack: don't bypass permissions check in inode_setsecctx hook

2024-09-1305:29:23

Linux

www.cve.org

linux kernel vulnerability

nfs client

security labels

permissions check

inode_setsecctx

lsm hooks

file security label

EPSS

Percentile

16.3%

JSON

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

selinux,smack: don’t bypass permissions check in inode_setsecctx hook

Marek Gresko reports that the root user on an NFS client is able to
change the security labels on files on an NFS filesystem that is
exported with root squashing enabled.

The end of the kerneldoc comment for __vfs_setxattr_noperm() states:

This function requires the caller to lock the inode’s i_mutex before it
is executed. It also assumes that the caller will make the appropriate
permission checks.

nfsd_setattr() does do permissions checking via fh_verify() and
nfsd_permission(), but those don’t do all the same permissions checks
that are done by security_inode_setxattr() and its related LSM hooks do.

Since nfsd_setattr() is the only consumer of security_inode_setsecctx(),
simplest solution appears to be to replace the call to
__vfs_setxattr_noperm() with a call to __vfs_setxattr_locked(). This
fixes the above issue and has the added benefit of causing nfsd to
recall conflicting delegations on a file when a client tries to change
its security label.

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "security/selinux/hooks.c",
      "security/smack/smack_lsm.c"
    ],
    "versions": [
      {
        "version": "1da177e4c3f4",
        "lessThan": "459584258d47",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1da177e4c3f4",
        "lessThan": "f71ec019257b",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1da177e4c3f4",
        "lessThan": "76a0e79bc84f",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "security/selinux/hooks.c",
      "security/smack/smack_lsm.c"
    ],
    "versions": [
      {
        "version": "6.6.49",
        "lessThanOrEqual": "6.6.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.10.8",
        "lessThanOrEqual": "6.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.11",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]