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Message-ID: <5bc9d707-b193-6111-fea6-50c70e6f2245@linux.microsoft.com>
Date: Tue, 6 Jul 2021 12:21:04 -0700
From: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
To: Roberto Sassu <roberto.sassu@...wei.com>, zohar@...ux.ibm.com,
paul@...l-moore.com
Cc: stephen.smalley.work@...il.com, prsriva02@...il.com,
tusharsu@...ux.microsoft.com, linux-integrity@...r.kernel.org,
linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org, selinux@...r.kernel.org
Subject: Re: [PATCH v3 2/3] ima: Return int in the functions to measure a
buffer
On 7/5/2021 2:09 AM, Roberto Sassu wrote:
> ima_measure_critical_data() and process_buffer_measurement() currently
> don't return a result. A caller wouldn't be able to know whether those
> functions were executed successfully.
>
> This patch modifies the return type from void to int, and returns 0 if the
> buffer has been successfully measured, a negative value otherwise.
>
> Also, this patch does not modify the behavior of existing callers by
> processing the returned value. For those, the return value is ignored.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> ---
> include/linux/ima.h | 15 +++++++-----
> security/integrity/ima/ima.h | 10 ++++----
> security/integrity/ima/ima_main.c | 40 ++++++++++++++++++-------------
> 3 files changed, 37 insertions(+), 28 deletions(-)
Reviewed-by: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
-lakshmi
>
> diff --git a/include/linux/ima.h b/include/linux/ima.h
> index 81e830d01ced..60492263aa64 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -35,10 +35,10 @@ extern void ima_post_path_mknod(struct user_namespace *mnt_userns,
> extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
> extern int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size);
> extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);
> -extern void ima_measure_critical_data(const char *event_label,
> - const char *event_name,
> - const void *buf, size_t buf_len,
> - bool hash);
> +extern int ima_measure_critical_data(const char *event_label,
> + const char *event_name,
> + const void *buf, size_t buf_len,
> + bool hash);
>
> #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
> extern void ima_appraise_parse_cmdline(void);
> @@ -144,10 +144,13 @@ static inline int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size
>
> static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {}
>
> -static inline void ima_measure_critical_data(const char *event_label,
> +static inline int ima_measure_critical_data(const char *event_label,
> const char *event_name,
> const void *buf, size_t buf_len,
> - bool hash) {}
> + bool hash)
> +{
> + return -ENOENT;
> +}
>
> #endif /* CONFIG_IMA */
>
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index f0e448ed1f9f..03db221324c3 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -264,11 +264,11 @@ 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 user_namespace *mnt_userns,
> - struct inode *inode, const void *buf, int size,
> - const char *eventname, enum ima_hooks func,
> - int pcr, const char *func_data,
> - bool buf_hash);
> +int process_buffer_measurement(struct user_namespace *mnt_userns,
> + struct inode *inode, const void *buf, int size,
> + const char *eventname, enum ima_hooks func,
> + int pcr, const char *func_data,
> + bool buf_hash);
> 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 8ef1fa357e0c..b512c06d8ee1 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -827,7 +827,7 @@ int ima_post_load_data(char *buf, loff_t size,
> return 0;
> }
>
> -/*
> +/**
> * process_buffer_measurement - Measure the buffer or the buffer data hash
> * @mnt_userns: user namespace of the mount the inode was found from
> * @inode: inode associated with the object being measured (NULL for KEY_CHECK)
> @@ -840,12 +840,15 @@ int ima_post_load_data(char *buf, loff_t size,
> * @buf_hash: measure buffer data hash
> *
> * Based on policy, either the buffer data or buffer data hash is measured
> + *
> + * Return: 0 if the buffer has been successfully measured, a negative value
> + * otherwise.
> */
> -void process_buffer_measurement(struct user_namespace *mnt_userns,
> - struct inode *inode, const void *buf, int size,
> - const char *eventname, enum ima_hooks func,
> - int pcr, const char *func_data,
> - bool buf_hash)
> +int process_buffer_measurement(struct user_namespace *mnt_userns,
> + struct inode *inode, const void *buf, int size,
> + const char *eventname, enum ima_hooks func,
> + int pcr, const char *func_data,
> + bool buf_hash)
> {
> int ret = 0;
> const char *audit_cause = "ENOMEM";
> @@ -867,7 +870,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns,
> u32 secid;
>
> if (!ima_policy_flag)
> - return;
> + return -ENOENT;
>
> template = ima_template_desc_buf();
> if (!template) {
> @@ -889,7 +892,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns,
> secid, 0, func, &pcr, &template,
> func_data);
> if (!(action & IMA_MEASURE))
> - return;
> + return -ENOENT;
> }
>
> if (!pcr)
> @@ -937,7 +940,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns,
> func_measure_str(func),
> audit_cause, ret, 0, ret);
>
> - return;
> + return ret;
> }
>
> /**
> @@ -977,18 +980,21 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
> * and extend the pcr. Examples of critical data could be various data
> * structures, policies, and states stored in kernel memory that can
> * impact the integrity of the system.
> + *
> + * Return: 0 if the buffer has been successfully measured, a negative value
> + * otherwise.
> */
> -void ima_measure_critical_data(const char *event_label,
> - const char *event_name,
> - const void *buf, size_t buf_len,
> - bool hash)
> +int ima_measure_critical_data(const char *event_label,
> + const char *event_name,
> + const void *buf, size_t buf_len,
> + bool hash)
> {
> if (!event_name || !event_label || !buf || !buf_len)
> - return;
> + return -ENOPARAM;
>
> - process_buffer_measurement(&init_user_ns, NULL, buf, buf_len, event_name,
> - CRITICAL_DATA, 0, event_label,
> - hash);
> + return process_buffer_measurement(&init_user_ns, NULL, buf, buf_len,
> + event_name, CRITICAL_DATA, 0,
> + event_label, hash);
> }
>
> static int __init init_ima(void)
>
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