Andy Lutomirski <luto@xxxxxxxxxxxxxx> writes: > On Fri, Dec 12, 2014 at 2:48 PM, Eric W. Biederman > <ebiederm@xxxxxxxxxxxx> wrote: >> 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. >> > > I thought I already fixed this. Did I miss part of it? My tree is based at 3.18-rc6 and as of there I don't see another fix. You fixed the remount_sb case in umount I don't think you fixed forced unmounts themselves. If you did fix this and can point me at it I will be happy to drop this patch. Eric >> Cc: stable@xxxxxxxxxxxxxxx >> Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> >> --- >> fs/namespace.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/fs/namespace.c b/fs/namespace.c >> index 3a1a87dc33df..43b16af8af30 100644 >> --- a/fs/namespace.c >> +++ b/fs/namespace.c >> @@ -1544,6 +1544,9 @@ 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: >> -- >> 1.9.1 >> -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html