From: "Ahmed S. Darwish" <darwish.07@gmail.com>
To: casey@schaufler-ca.com
Cc: akpm@osdl.org, torvalds@osdl.org,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] Version 9 (2.6.24-rc1) Smack: Simplified Mandatory Access Control Kernel
Date: Sat, 27 Oct 2007 11:01:12 +0200 [thread overview]
Message-ID: <20071027090112.GA5460@Ahmed> (raw)
In-Reply-To: <4720118C.5020906@schaufler-ca.com>
> +/**
> + * smk_write_cipso - write() for /smack/cipso
> + * @filp: file pointer, not actually used
> + * @buf: where to get the data from
> + * @count: bytes sent
> + * @ppos: where to start
> + *
> + * Returns number of bytes written or error code, as appropriate
> + */
> +static ssize_t smk_write_cipso(struct file *file, const char __user *buf,
> + size_t count, loff_t *ppos)
> +{
[...]
> +
> + /*
> + * Only allow one writer at a time. Writes should be
> + * quite rare and small in any case.
> + */
> + mutex_lock(&smack_cipso_lock);
> +
> + *(data + count) = '\0';
> +
> + for (eolp = strchr(data, '\n'), linep = data;
> + eolp != NULL && rc >= 0;
> + linep = eolp + 1, eolp = strchr(linep, '\n')) {
> +
The problem here (As discussed in private mails) is that the for loop
assumes that the beginning of given user-space buffer is the beginning
of a rule. This leads to situations where the rule becomes "ecret 20",
or "cret 20" instead of "Secret 20". Big input buffers/files leads
smack to recieve a rule like "Secret 20" in fragmented chunks like:
write("<lots of rules before ours>\nSec", ..)
write("r", 1, ..)
write("et 20\n<remaing rules after ours>", ..)
Parsing a rule in such tough conditions in _kernel space_ is very
hard. I began to feel that it will be much easier if we do the parsing
in a userspace utility and let smack accept only small buffers (80 char).
i.e. A user space utility that takes a big input file like
exit 10/3,7,4
exit 10/3,7,4
exit 10/3,7,4
<100 times>
And transform it to 100 small write() calls. By this way we can return
-EINVAL if write()'s count field > 80, or if input contains no \n or
more than one.
Any Ideas ?.
Casey, I can begin modifying cipso_write() and writing this small
user-space utility now if you agree on this.
Regards,
--
Ahmed S. Darwish
HomePage: http://darwish.07.googlepages.com
Blog: http://darwish-07.blogspot.com
next prev parent reply other threads:[~2007-10-27 20:59 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-10-25 3:46 [PATCH 2/2] Version 9 (2.6.24-rc1) Smack: Simplified Mandatory Access Control Kernel Casey Schaufler
2007-10-25 15:07 ` Stephen Smalley
2007-10-25 18:58 ` Casey Schaufler
2007-10-26 20:34 ` Stephen Smalley
2007-10-27 3:00 ` Ahmed S. Darwish
2007-10-27 19:20 ` Casey Schaufler
2007-10-27 9:01 ` Ahmed S. Darwish [this message]
2007-10-27 23:47 ` Al Viro
2007-10-28 5:41 ` Casey Schaufler
2007-10-28 12:46 ` Ahmed S. Darwish
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