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authorEric W. Biederman <ebiederm@xmission.com>2014-07-28 16:26:53 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-09-17 09:04:00 -0700
commit8c30f22757c97041750fddce8ea11c6d7231574a (patch)
tree94ba7186877ce10a5129339f4c15f6098a2227e8 /fs
parent7f70b62ea0f72edae160ddf540723991b84c8279 (diff)
mnt: Only change user settable mount flags in remount
commit a6138db815df5ee542d848318e5dae681590fccd upstream. Kenton Varda <kenton@sandstorm.io> discovered that by remounting a read-only bind mount read-only in a user namespace the MNT_LOCK_READONLY bit would be cleared, allowing an unprivileged user to the remount a read-only mount read-write. Correct this by replacing the mask of mount flags to preserve with a mask of mount flags that may be changed, and preserve all others. This ensures that any future bugs with this mask and remount will fail in an easy to detect way where new mount flags simply won't change. Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/namespace.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index a45ba4f267fe..a438e4c81b0b 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1805,7 +1805,7 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
err = do_remount_sb(sb, flags, data, 0);
if (!err) {
br_write_lock(&vfsmount_lock);
- mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK;
+ mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
mnt->mnt.mnt_flags = mnt_flags;
br_write_unlock(&vfsmount_lock);
}