Re: [BUG] 3ce1217d6cd5 ima patch causes s390 to crash on boot

[Roberto Sassu]

On 11/22/2013 05:35 PM, Heiko Carstens wrote:
> On Fri, Nov 22, 2013 at 05:23:49PM +0100, Roberto Sassu wrote:
> > Another problem that I found is that strsep()
> > modifies the source buffer by replacing the separator
> > character with '\0'. In particular, this function
> > modifies static data initialized at the beginning
> > of the ima_template.c file. Maybe, this is causing
> > the kernel panic. I already sent a patch to fix this
> > problem (attached to the email) even if it is not
> > supposed to land on the 3.13 kernel. Let me know
> > if this fixes the issue. Otherwise, I will check
> > the code more in depth.
>
> With your patch below applied the kernel boots again.
> So it should go into 3.13 (or a different fix).

Ok, good. Yes, we will apply this patch to the 3.13 kernel.


> Thanks!

No problem.

Roberto


> >  From 2d3aa1c0328c44ecc3af7de162791c8cddfb6dfd Mon Sep 17 00:00:00 2001
> > From: Roberto Sassu <roberto.sassu@xxxxxxxxx>
> > Date: Wed, 6 Nov 2013 13:51:35 +0100
> > Subject: [RFC][PATCH 2/4] ima: make a copy of template_fmt in
> >   template_desc_init_fields()
> >
> > This patch makes a copy of the 'template_fmt' function argument so that
> > the latter will not be modified by strsep(), which does the splitting by
> > replacing the given separator with '\0'.
> >
> > Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxx>
> > ---
> >   security/integrity/ima/ima_template.c | 9 ++++++++-
> >   1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
> > index 7bcff5c..bb33576 100644
> > --- a/security/integrity/ima/ima_template.c
> > +++ b/security/integrity/ima/ima_template.c
> > @@ -113,13 +113,19 @@ static int template_desc_init_fields(char *template_fmt,
> >   				     struct ima_template_field ***fields,
> >   				     int *num_fields)
> >   {
> > -	char *c, *template_fmt_ptr = template_fmt;
> > +	char *c, *template_fmt_ptr, *template_fmt_copy = NULL;
> >   	int template_num_fields = template_fmt_size(template_fmt);
> >   	int i, result = 0;
> >
> >   	if (template_num_fields > IMA_TEMPLATE_NUM_FIELDS_MAX)
> >   		return -EINVAL;
> >
> > +	/* copying is needed as strsep() modifies the original buffer */
> > +	template_fmt_copy = kstrdup(template_fmt, GFP_KERNEL);
> > +	if (template_fmt_copy == NULL)
> > +		return -ENOMEM;
> > +
> > +	template_fmt_ptr = template_fmt_copy;
> >   	*fields = kzalloc(template_num_fields * sizeof(*fields), GFP_KERNEL);
> >   	if (*fields == NULL) {
> >   		result = -ENOMEM;
> > @@ -139,6 +145,7 @@ static int template_desc_init_fields(char *template_fmt,
> >   	*num_fields = i;
> >   	return 0;
> >   out:
> > +	kfree(template_fmt_copy);
> >   	kfree(*fields);
> >   	*fields = NULL;
> >   	return result;
> > --
> > 1.8.1.4

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