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Stephen Smalley 28b7260548 selinux: preserve NATIVE_LABELS on already-initialized sb in set_mnt_opts ...

When an NFSv4 filesystem exported with security_label is mounted a
second time, sget_fc() returns the existing superblock and
nfs_get_root() calls security_sb_set_mnt_opts() again on it. Since the
superblock is already SB_INITIALIZED, selinux_set_mnt_opts() takes an
early exit without setting SECURITY_LSM_NATIVE_LABELS in
*set_kern_flags. nfs_get_root() then sees kflags without
SECURITY_LSM_NATIVE_LABELS set and clears NFS_CAP_SECURITY_LABEL on
the shared nfs_server, silently disabling per-file labeling for both
the new and the original mount.

Commit 3815a245b5 ("security/selinux: fix SECURITY_LSM_NATIVE_LABELS
on reused superblock") fixed the same problem in
selinux_sb_clone_mnt_opts().  The reused-superblock path for a plain
second mount now goes through sb_set_mnt_opts rather than
sb_clone_mnt_opts, so it needs the same treatment: on both
SE_SBINITIALIZED early exits, set SECURITY_LSM_NATIVE_LABELS in
*set_kern_flags when the superblock was already using
SECURITY_FS_USE_NATVE.

Cc: stable@vger.kernel.org
Closes: https://github.com/SELinuxProject/selinux-kernel/issues/69
Closes: https://github.com/SELinuxProject/selinux-kernel/issues/70
Closes: https://github.com/SELinuxProject/selinux-testsuite/issues/91
Closes: https://github.com/SELinuxProject/selinux-testsuite/issues/92
Fixes: eb9ae68650 ("SELinux: Add new labeling type native labels")
Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

2026-09-30 15:10:41 -04:00

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