Re: [PATCH v2 4/7] fs/proc/task_mmu.c: shift mm_access() from m_start() to proc_maps_open()

On 12/03, Kirill A. Shutemov wrote:

On Tue, Aug 05, 2014 at 09:46:55PM +0200, Oleg Nesterov wrote:

quoted

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

Yes, there are more lock_trace/mm_access (ab)users. Fortunately, they
are much simpler than proc/pid/maps (which also asked for other cleanups
and fixes).

I'll try to take a look, thanks for reminding.

And I agree with Eric, chmod+x probably makes no sense. Still I think
this code deserves some cleanups regardless. To the point I think that
lock_trace() should probably die.

Thanks!

Oleg.