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authorEric W. Biederman <ebiederm@xmission.com>2014-07-28 16:26:53 -0700
committerEric W. Biederman <ebiederm@xmission.com>2014-07-31 17:11:54 -0700
commita6138db815df5ee542d848318e5dae681590fccd (patch)
tree52f996bcb8b01b4d1e4ee3705c0f646e549fa41a /fs/namespace.c
parent728dba3a39c66b3d8ac889ddbe38b5b1c264aec3 (diff)
downloadlwn-a6138db815df5ee542d848318e5dae681590fccd.tar.gz
lwn-a6138db815df5ee542d848318e5dae681590fccd.zip
mnt: Only change user settable mount flags in remount
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. Cc: stable@vger.kernel.org Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'fs/namespace.c')
-rw-r--r--fs/namespace.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index 7187d01329c3..cb40449ea0df 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1937,7 +1937,7 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
err = do_remount_sb(sb, flags, data, 0);
if (!err) {
lock_mount_hash();
- 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;
touch_mnt_namespace(mnt->mnt_ns);
unlock_mount_hash();