Commit 5f20adea authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Greg Kroah-Hartman
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umount: Disallow unprivileged mount force 



commit b2f5d4dc upstream.

Forced unmount affects not just the mount namespace but the underlying
superblock as well.  Restrict forced unmount to the global root user
for now.  Otherwise it becomes possible a user in a less privileged
mount namespace to force the shutdown of a superblock of a filesystem
in a more privileged mount namespace, allowing a DOS attack on root.

Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent ebdd0940

fs/namespace.c

+3 −0
Original line number Diff line number Diff line
@@ -1441,6 +1441,9 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags) 
		goto dput_and_out;

	if (mnt->mnt.mnt_flags & MNT_LOCKED)

		goto dput_and_out;

	retval = -EPERM;

	if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))

		goto dput_and_out;



	retval = do_umount(mnt, flags);

dput_and_out: