On Thu, 2020-08-27 at 18:57 -0700, Tushar Sugandhi wrote:
> process_buffer_measurement() does not return the result of the operation.
> Therefore, the consumers of this function cannot act on it, if needed.
>
> Update return type of process_buffer_measurement() from void to int.
Failure to measure may be audited, but should never fail. This is one
of the main differences between secure and trusted boot concepts.
Notice in process_measurement() that -EACCES is only returned for
appraisal.
Returning a failure from process_buffer_measurement() in itself isn't a
problem, as long as the failure isn't returned to the LSM/IMA hook.
However, just as the callers of process_measurement() originally
processed the result, that processing was moved into
process_measurement() [1].
Mimi
[1] 750943a30714 ima: remove enforce checking duplication
>
> Signed-off-by: Tushar Sugandhi <tusha...@linux.microsoft.com>
> ---
> security/integrity/ima/ima.h | 6 +++---
> security/integrity/ima/ima_main.c | 14 +++++++-------
> 2 files changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index 8875085db689..83ed57147e68 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -265,9 +265,9 @@ void ima_store_measurement(struct integrity_iint_cache
> *iint, struct file *file,
> struct evm_ima_xattr_data *xattr_value,
> int xattr_len, const struct modsig *modsig, int pcr,
> struct ima_template_desc *template_desc);
> -void process_buffer_measurement(struct inode *inode, const void *buf, int
> size,
> - const char *eventname, enum ima_hooks func,
> - int pcr, const char *func_data);
> +int process_buffer_measurement(struct inode *inode, const void *buf, int
> size,
> + const char *eventname, enum ima_hooks func,
> + int pcr, const char *func_data);
> void ima_audit_measurement(struct integrity_iint_cache *iint,
> const unsigned char *filename);
> int ima_alloc_init_template(struct ima_event_data *event_data,
> diff --git a/security/integrity/ima/ima_main.c
> b/security/integrity/ima/ima_main.c
> index c870fd6d2f83..0979a62a9257 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -736,9 +736,9 @@ int ima_load_data(enum kernel_load_data_id id)
> *
> * Based on policy, the buffer is measured into the ima log.
> */
> -void process_buffer_measurement(struct inode *inode, const void *buf, int
> size,
> - const char *eventname, enum ima_hooks func,
> - int pcr, const char *func_data)
> +int process_buffer_measurement(struct inode *inode, const void *buf, int
> size,
> + const char *eventname, enum ima_hooks func,
> + int pcr, const char *func_data)
> {
> int ret = 0;
> const char *audit_cause = "ENOMEM";
> @@ -758,7 +758,7 @@ void process_buffer_measurement(struct inode *inode,
> const void *buf, int size,
> u32 secid;
>
> if (!ima_policy_flag)
> - return;
> + return 0;
>
> /*
> * Both LSM hooks and auxilary based buffer measurements are
> @@ -772,7 +772,7 @@ void process_buffer_measurement(struct inode *inode,
> const void *buf, int size,
> action = ima_get_action(inode, current_cred(), secid, 0, func,
> &pcr, &template, func_data);
> if (!(action & IMA_MEASURE))
> - return;
> + return 0;
> }
>
> if (!pcr)
> @@ -787,7 +787,7 @@ void process_buffer_measurement(struct inode *inode,
> const void *buf, int size,
> pr_err("template %s init failed, result: %d\n",
> (strlen(template->name) ?
> template->name : template->fmt), ret);
> - return;
> + return ret;
> }
> }
>
> @@ -819,7 +819,7 @@ void process_buffer_measurement(struct inode *inode,
> const void *buf, int size,
> func_measure_str(func),
> audit_cause, ret, 0, ret);
>
> - return;
> + return ret;
> }
>
> /**
