linux-kernel - Re: [AppArmor 37/41] AppArmor: Main Part

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Date:	Thu, 12 Apr 2007 11:37:23 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	jjohansen@...e.de
Cc:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, chrisw@...s-sol.org,
	John Johansen <jjohansen@...e.de>,
	Andreas Gruenbacher <agruen@...e.de>
Subject: Re: [AppArmor 37/41] AppArmor: Main Part

> + * aa_taskattr_access
> + * @name: name of the file to check
> + *
> + * Check if name matches /proc/self/attr/current, with self resolved
> + * to the current pid. This file is the usermode iterface for
> + * changing one's hat.
> + */
> +static inline int aa_taskattr_access(const char *name)
> +{
> +	unsigned long pid;
> +	char *end;
> +
> +	if (strncmp(name, "/proc/", 6) != 0)
> +		return 0;

The proc file system may not be mounted at /proc. There are environments
where this is done for good reason (eg not wanting the /proc info exposed
to a low trust environment). Another is when FUSE is providing an
arbitrated proc either by merging across clusters or by removing stuff.

> +static int aa_file_denied(struct aa_profile *profile, const char *name,
> +			  int mask)
> +{
> +	int perms;
> +
> +	/* Always allow write access to /proc/self/attr/current. */
> +	if (mask == MAY_WRITE && aa_taskattr_access(name))
> +		return 0;

Why can't this be done in the profile itself to avoid kernel special case
uglies and inflexibility ?

> +		if (PTR_ERR(sa->name) == -ENOENT && (check & AA_CHECK_FD))
> +			denied_mask = 0;

Now there is an interesting question. Is PTR_ERR() safe for kernel
pointers on all platforms or just for user ones ?


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