From: "Eric W. Biederman" <[email protected]> commit a6138db815df5ee542d848318e5dae681590fccd upstream.
Kenton Varda <[email protected]> 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 <[email protected]> Signed-off-by: "Eric W. Biederman" <[email protected]> [ luis: backported to 3.11: adjusted context ] Signed-off-by: Luis Henriques <[email protected]> --- fs/namespace.c | 2 +- include/linux/mount.h | 4 +++- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index ad8ea9bc2518..c98baa23e4d8 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); } diff --git a/include/linux/mount.h b/include/linux/mount.h index 73005f9957ea..16fc05d816d4 100644 --- a/include/linux/mount.h +++ b/include/linux/mount.h @@ -42,7 +42,9 @@ struct mnt_namespace; * flag, consider how it interacts with shared mounts. */ #define MNT_SHARED_MASK (MNT_UNBINDABLE) -#define MNT_PROPAGATION_MASK (MNT_SHARED | MNT_UNBINDABLE) +#define MNT_USER_SETTABLE_MASK (MNT_NOSUID | MNT_NODEV | MNT_NOEXEC \ + | MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME \ + | MNT_READONLY) #define MNT_INTERNAL 0x4000 -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
