linux-kernel - Re: [PATCH] vfs: fix IMA lockdep circular locking dependency

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Message-ID: <CA+55aFzP8Eo1AX7MS-RRG_Atq3NF0bS1ReZydRtgxxy7TDn57Q@mail.gmail.com>
Date:	Wed, 30 May 2012 15:51:27 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Eric Paris <eparis@...isplace.org>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Mimi Zohar <zohar@...ibm.com>,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vfs: fix IMA lockdep circular locking dependency

On Wed, May 30, 2012 at 2:36 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>
> The only difference is that for file-backed ones !MMU wants
> VM_MAYEXEC in that file's bdi flags (BDI_CAP_EXEC_MAP).  And
> that actually sounds reasonable in !MMU case.

Ok, I don't think it should be strictly necessary, but I guess I don't
mind either.

> Anyway, I've dumped the variant I've got into vfs.git@...urity_file_mmap;
> it should be at commit f12a0fd062b1d259a0b6bc6442019e6d4c45e9f5.
>
> Comments?

Two small ones:

 - I really don't think you should use "goto out" in
security_mmap_file(). That implies that you're exiting the function,
but in fact you're jumping to the very *meat* of the function.

   So I think you should rename "out" as "no_added_exec" or something.

And a small question:  This code:

+       ret = security_mmap_file(file, prot, flags);
+       if (!ret) {
+               down_write(&current->mm->mmap_sem);
+               retval = do_mmap_pgoff(file, addr, len, prot, flags, pgoff);
+               up_write(&current->mm->mmap_sem);
+       }

now seems to exist in four places. And in fact, that pretty much seems
to *be* what vm_mmap() is, at this point. Why isn't there just one
single vm_mmap() implementation, and then the callers of that?

                    Linus
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