linux-kernel - Re: [PATCH v11 2/9] ima: define and call ima_alloc_kexec_file

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Message-ID: <Z/SoekIdreYI3uBZ@MiWiFi-R3L-srv>
Date: Tue, 8 Apr 2025 12:39:22 +0800
From: Baoquan He <bhe@...hat.com>
To: Mimi Zohar <zohar@...ux.ibm.com>
Cc: steven chen <chenste@...ux.microsoft.com>, stefanb@...ux.ibm.com,
	roberto.sassu@...weicloud.com, roberto.sassu@...wei.com,
	eric.snowberg@...cle.com, ebiederm@...ssion.com,
	paul@...l-moore.com, code@...icks.com, bauermann@...abnow.com,
	linux-integrity@...r.kernel.org, kexec@...ts.infradead.org,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org,
	madvenka@...ux.microsoft.com, nramas@...ux.microsoft.com,
	James.Bottomley@...senpartnership.com, vgoyal@...hat.com,
	dyoung@...hat.com
Subject: Re: [PATCH v11 2/9] ima: define and call ima_alloc_kexec_file_buf()

On 04/08/25 at 12:07am, Mimi Zohar wrote:
> On Wed, 2025-04-02 at 05:47 -0700, steven chen wrote:
> > In the current implementation, the ima_dump_measurement_list() API is 
> > called during the kexec "load" phase, where a buffer is allocated and 
> > the measurement records are copied. Due to this, new events added after
> > kexec load but before kexec execute are not carried over to the new kernel
> > during kexec operation
> 
> Repeating this here is unnecessary.
> > 
> > To allow the buffer allocation and population to be separated into distinct
> > steps, make the function local seq_file "ima_kexec_file" to a file variable.
> 
> This change was already made in [PATCH v11 1/9] ima: rename variable the
> set_file "file" to "ima_kexec_file".  Please remove.
> 
> > 
> > Carrying the IMA measurement list across kexec requires allocating a
> > buffer and copying the measurement records.  Separate allocating the
> > buffer and copying the measurement records into separate functions in
> > order to allocate the buffer at kexec 'load' and copy the measurements
> > at kexec 'execute'.
> > 
> > Signed-off-by: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
> > Signed-off-by: steven chen <chenste@...ux.microsoft.com>
> > ---
> >  security/integrity/ima/ima_kexec.c | 46 +++++++++++++++++++++++-------
> >  1 file changed, 35 insertions(+), 11 deletions(-)
> > 
> > diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
> > index 650beb74346c..b12ac3619b8f 100644
> > --- a/security/integrity/ima/ima_kexec.c
> > +++ b/security/integrity/ima/ima_kexec.c
> > @@ -15,26 +15,46 @@
> >  #include "ima.h"
> >  
> >  #ifdef CONFIG_IMA_KEXEC
> > +static struct seq_file ima_kexec_file;
> > +
> > +static void ima_free_kexec_file_buf(struct seq_file *sf)
> > +{
> > +	vfree(sf->buf);
> > +	sf->buf = NULL;
> > +	sf->size = 0;
> > +	sf->read_pos = 0;
> > +	sf->count = 0;
> > +}
> > +
> > +static int ima_alloc_kexec_file_buf(size_t segment_size)
> > +{
> > +	ima_free_kexec_file_buf(&ima_kexec_file);
> 
> After moving the vfree() here at this stage in the patch set, the IMA
> measurement list fails to verify when doing two consecutive "kexec -s -l"
> with/without a "kexec -s -u" in between.  Only after "ima: kexec: move IMA log
> copy from kexec load to execute" the IMA measurement list verifies properly with
> the vfree() here.

I also noticed this, patch 7 will remedy this. Put patch 7 just after
this patch or squash it into this patch?

[PATCH v11 7/9] ima: verify if the segment size has changed

> 
> > +
> > +	/* segment size can't change between kexec load and execute */
> > +	ima_kexec_file.buf = vmalloc(segment_size);
> > +	if (!ima_kexec_file.buf)
> > +		return -ENOMEM;
> > +
> > +	ima_kexec_file.size = segment_size;
> > +	ima_kexec_file.read_pos = 0;
> > +	ima_kexec_file.count = sizeof(struct ima_kexec_hdr);	/* reserved space */
> > +
> > +	return 0;
> > +}
> > +
>