Date: Thu, 08 Mar 2018 14:20:17 -0500 From: Mimi Zohar <zohar@...ux.vnet.ibm.com> To: Tycho Andersen <tycho@...ho.ws> Cc: Andy Shevchenko <andy.shevchenko@...il.com>, Dmitry Kasatkin <dmitry.kasatkin@...il.com>, linux-integrity@...r.kernel.org, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, kernel-hardening@...ts.openwall.com, Richard Guy Briggs <rgb@...hat.com> Subject: Re: [PATCH] ima: drop vla in ima_audit_measurement() On Thu, 2018-03-08 at 12:04 -0700, Tycho Andersen wrote: > On Thu, Mar 08, 2018 at 01:50:30PM -0500, Mimi Zohar wrote: > > On Thu, 2018-03-08 at 11:37 -0700, Tycho Andersen wrote: > > > On Thu, Mar 08, 2018 at 07:47:37PM +0200, Andy Shevchenko wrote: > > > > On Thu, Mar 8, 2018 at 7:14 PM, Tycho Andersen <tycho@...ho.ws> wrote: > > > > > In keeping with the directive to get rid of VLAs , let's drop the VLA > > > > > from ima_audit_measurement(). We need to adjust the return type of > > > > > ima_audit_measurement, because now this function can fail if an allocation > > > > > fails. > > > > > > > > > > > > > > > > > + algo_hash_len = hash_len + strlen(algo_name) + 2; > > > > > + algo_hash = kzalloc(algo_hash_len, GFP_KERNEL); > > > > > > > > > - snprintf(algo_hash, sizeof(algo_hash), "%s:%s", algo_name, hash); > > > > > + snprintf(algo_hash, algo_hash_len, "%s:%s", algo_name, hash); > > > > > > > > kasprintf() ? > > > > > > Sure, in fact I think we could just do: > > > > > > - snprintf(algo_hash, algo_hash_len, "%s:%s", algo_name, hash); > > > - audit_log_untrustedstring(ab, algo_hash); > > > + audit_log_untrustedstring(ab, algo_name); > > > + audit_log_format(ab, ":"); > > > + audit_log_untrustedstring(ab, hash); > > > > > > and get rid of the allocation entirely. I'll test and make sure it > > > works and then re-send. > > > > The hash algorithm name is an enumeration that comes from the kernel. > > It's defined in crypto/hash_info.c: hash_algo_name. Why do we need > > to use audit_log_untrustedstring()? > > Yes, I suppose we don't need it for the hash either, since we're > generating that and we know it's just hex digits and not any audit > control characters or "s or anything. > > It looks like we could get rid of the other allocation too by just > using audit_log_n_hex, but that uses hex_byte_pack_upper, vs. the > hex_byte_pack that's currently in use in this function. Is that too > much of a breakage? Based on the discussion with Richard Briggs, we need to differentiate between the ima_audit_measurement() and the ima_parse_rule() usage of AUDIT_INTEGRITY_RULE. The ima_parse_rule() will continue to use AUDIT_INTEGRITY_RULE. ima_audit_measurement() will need to define and use a new number. Auidt name suggestions would be appreciated. When we make that sort of change, any other changes are insignificant. How different are the two formats? Mimi
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