linux-kernel - ima_mmap_file returning 0 to userspace as mmap result.

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Message-ID: <20140604233122.GA19838@redhat.com>
Date:	Wed, 4 Jun 2014 19:31:22 -0400
From:	Dave Jones <davej@...hat.com>
To:	Linux Kernel <linux-kernel@...r.kernel.org>
Cc:	mtk.manpages@...il.com, linux-mm@...ck.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	zohar@...ux.vnet.ibm.com
Subject: ima_mmap_file returning 0 to userspace as mmap result.

I just noticed that trinity was freaking out in places when mmap was
returning zero.  This surprised me, because I had the mmap_min_addr
sysctl set to 64k, so it wasn't a MAP_FIXED mapping that did it.

There's no mention of this return value in the man page, so I dug
into the kernel code, and it appears that we do..

sys_mmap
vm_mmap_pgoff
security_mmap_file
ima_file_mmap <- returns 0 if not PROT_EXEC

and then the 0 gets propagated up as a retval all the way to userspace.

It smells to me like we might be violating a standard or two here, and
instead of 0 ima should be returning -Esomething

thoughts?

	Dave

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