On Wed, Dec 03, 2014 at 10:59:57AM -0600, Eric W. Biederman wrote: > "Kirill A. Shutemov" <[email protected]> writes: > > > On Tue, Aug 05, 2014 at 09:46:55PM +0200, Oleg Nesterov wrote: > >> A simple test-case from Kirill Shutemov > >> > >> cat /proc/self/maps >/dev/null > >> chmod +x /proc/self/net/packet > >> exec /proc/self/net/packet > >> > >> makes lockdep unhappy, cat/exec take seq_file->lock + cred_guard_mutex in > >> the opposite order. > > > > Oleg, I see it again with almost the same test-case: > > > > cat /proc/self/stack >/dev/null > > chmod +x /proc/self/net/packet > > exec /proc/self/net/packet > > > > Looks like bunch of proc files were converted to use seq_file by Alexey > > Dobriyan around the same time you've fixed the issue for /proc/pid/maps. > > > > More generic test-case: > > > > find /proc/self/ -type f -exec dd if='{}' of=/dev/null bs=1 count=1 ';' > > 2>/dev/null > > chmod +x /proc/self/net/packet > > exec /proc/self/net/packet > > > > David, any justification for allowing chmod +x for files under > > /proc/pid/net? > > I don't think there are any good reasons for allowing chmod +x for the > proc generic files. Certainly executing any of them is nonsense. > > I do recall some weird conner cases existing. I think they resulted > in a need to preserve chmod if not chmod +x. This is just me saying > tread carefully before you change anything. > > It really should be safe to tweak proc_notify_change to not allow > messing with the executable bits of proc files.
BTW, we have MS_NOSUID and MS_NOEXEC set in ->s_flags for procfs since 2006 -- see 92d032855e64. But there's no code which would translate them into vfsmount->mnt_flags |= MNT_NOSUID/MNT_NOEXEC and we bypast nosuid/noexec checks on exec path. Hm?.. -- Kirill A. Shutemov -- 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/
