Re: [PATCH v7 1/7] ima: define and call ima_alloc_kexec_file_buf

[steven chen]

On 2/7/2025 11:10 AM, Mimi Zohar wrote:
> On Mon, 2025-02-03 at 15:20 -0800, steven chen wrote:
> > 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'.
> >
> > This patch includes the following changes:
> >   - Refactor ima_dump_measurement_list() to move the memory allocation
> >     to a separate function ima_alloc_kexec_file_buf() which allocates
> >     buffer of size 'kexec_segment_size' at kexec 'load'.
> >   - Make the local variable ima_kexec_file in ima_dump_measurement_list()
> >     a local static to the file, so that it can be accessed from
> >     ima_alloc_kexec_file_buf(). Compare actual memory required to ensure
> >     there is enough memory for the entire measurement record.
> >   - Copy as many measurement events as possible.
> >   - Make necessary changes to the function ima_add_kexec_buffer() to call
> >     the above two functions.
> >   - Compared the memory size allocated with memory size of the entire
> >     measurement record. If there is not enough memory, it will copy as many
> >     IMA measurement records as possible, and this situation will result
> >     in a failure of remote attestation.
> >
> > Author: Tushar Sugandhi <tusharsu@xxxxxxxxxxxxxxxxxxx>
> > Reviewed-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
> > Suggested-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
> > Signed-off-by: Tushar Sugandhi <tusharsu@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: steven chen <chenste@xxxxxxxxxxxxxxxxxxx>
> > ---
> >   security/integrity/ima/ima.h       |   1 +
> >   security/integrity/ima/ima_kexec.c | 105 +++++++++++++++++++++--------
> >   security/integrity/ima/ima_queue.c |   4 +-
> >   3 files changed, 80 insertions(+), 30 deletions(-)
> >
> > diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> > index 3c323ca213d4..447a6eb07c2d 100644
> > --- a/security/integrity/ima/ima.h
> > +++ b/security/integrity/ima/ima.h
> > @@ -274,6 +274,7 @@ bool ima_template_has_modsig(const struct ima_template_desc
> > *ima_template);
> >   int ima_restore_measurement_entry(struct ima_template_entry *entry);
> >   int ima_restore_measurement_list(loff_t bufsize, void *buf);
> >   int ima_measurements_show(struct seq_file *m, void *v);
> > +int ima_get_binary_runtime_entry_size(struct ima_template_entry *entry);
> >   unsigned long ima_get_binary_runtime_size(void);
> >   int ima_init_template(void);
> >   void ima_init_template_list(void);
> > diff --git a/security/integrity/ima/ima_kexec.c
> > b/security/integrity/ima/ima_kexec.c
> > index 52e00332defe..b60a902460e2 100644
> > --- a/security/integrity/ima/ima_kexec.c
> > +++ b/security/integrity/ima/ima_kexec.c
> > @@ -15,62 +15,99 @@
> >   #include "ima.h"
> >   
> >   #ifdef CONFIG_IMA_KEXEC
> > +static struct seq_file ima_kexec_file;
> > +
> > +static void ima_reset_kexec_file(struct seq_file *sf)
> > +{
> > +	sf->buf = NULL;
> > +	sf->size = 0;
> > +	sf->read_pos = 0;
> > +	sf->count = 0;
> > +}
> > +
> > +static void ima_free_kexec_file_buf(struct seq_file *sf)
> > +{
> > +	vfree(sf->buf);
> > +	ima_reset_kexec_file(sf);
> > +}
> > +
> > +static int ima_alloc_kexec_file_buf(size_t segment_size)
> > +{
> > +	/*
> > +	 * kexec 'load' may be called multiple times.
> > +	 * Free and realloc the buffer only if the segment_size is
> > +	 * changed from the previous kexec 'load' call.
> > +	 */
> > +	if (ima_kexec_file.buf &&
> > +		(ima_kexec_file.size == segment_size)) {
> > +		goto out;
> > +	}
> Nice cleanup from v5.  The line doesn't doesn't need to be split.  Both the
> parenthesis and the brackets can be removed.
>
> In the future, before posting patches, please use scripts/checkpatch.pl.
>
> CHECK: Unnecessary parentheses around 'ima_kexec_file.size == segment_size'
> #82: FILE: security/integrity/ima/ima_kexec.c:41:
> +	if (ima_kexec_file.buf &&
> +		(ima_kexec_file.size == segment_size)) {
>
> CHECK: Alignment should match open parenthesis
> #83: FILE: security/integrity/ima/ima_kexec.c:42:
> +	if (ima_kexec_file.buf &&
> +		(ima_kexec_file.size == segment_size)) {
>
> Or simply join the two lines.
>
> thanks,
>
> Mimi
>
> > +
> > +	ima_free_kexec_file_buf(&ima_kexec_file);
> > +
> > +	/* 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;
> > +
> > +out:
> > +	ima_kexec_file.read_pos = 0;
> > +	ima_kexec_file.count = sizeof(struct ima_kexec_hdr);	/* reserved space
> > */
> > +
> > +	return 0;
> > +}
Thanks, Mimi, will update in the next release