linux-kernel - Re: [PATCH 11/12] AppArmor: LSM interface, and security module initialization

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Date:	Mon, 9 Nov 2009 10:20:45 -0500
From:	Eric Paris <eparis@...isplace.org>
To:	John Johansen <john.johansen@...onical.com>
Cc:	linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [PATCH 11/12] AppArmor: LSM interface, and security module 
	initialization

On Tue, Nov 3, 2009 at 6:48 PM, John Johansen
<john.johansen@...onical.com> wrote:
> AppArmor hooks to interface with the LSM, and module parameters and
> initialization.
>
> Signed-off-by: John Johansen <john.johansen@...onical.com>
> ---


> +static int apparmor_file_mmap(struct file *file, unsigned long reqprot,
> +                             unsigned long prot, unsigned long flags,
> +                             unsigned long addr, unsigned long addr_only)
> +{
> +       int rc = 0;
> +       struct aa_profile *profile = aa_current_profile_wupd();
> +       /*
> +        * test before cap_file_mmap.  For confined tasks AppArmor will
> +        * enforce the mmap value set in the profile or default
> +        * to LSM_MMAP_MIN_ADDR
> +        */
> +       if (profile) {
> +               if (profile->flags & PFLAG_MMAP_MIN_ADDR) {
> +                       if (addr < profile->mmap_min_addr)
> +                               rc = -EACCES;
> +               } else if (addr < CONFIG_LSM_MMAP_MIN_ADDR) {
> +                       rc = -EACCES;
> +               }
> +               if (rc) {
> +                       struct aa_audit sa = {
> +                               .operation = "file_mmap",
> +                               .gfp_mask = GFP_KERNEL,
> +                               .info = "addr < mmap_min_addr",
> +                               .error = rc,
> +                       };
> +                       return aa_audit(AUDIT_APPARMOR_DENIED, profile, &sa,
> +                                       NULL);
> +               }
> +       }
> +       rc = cap_file_mmap(file, reqprot, prot, flags, addr, addr_only);
> +       if (rc || addr_only)
> +               return rc;
> +
> +       return common_mmap(file, "file_mmap", prot, flags);
> +}

There is a reason we do the round_hint_to_min() stuff in the vm and we
recalculate that value every time dac_mmap_min_addr is change.  It's
because mmap (NOT MAP_FIXED) with a hint < profile->mmap_min_addr is
going to end up getting denied here since the VM is going to assign it
the address it wanted instead of find a new address and you are going
to deny that task.

If profile() is a per task thing, I think you are in a failed
situation and can't solve the problem wtihout intrusive VFS hooks.  If
profile is a global thing just update that global value.  In either
case, this code is wrong....

-Eric
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