diff mbox series

[v3,04/24] powerpc/secvar: Handle format string in the consumer

Message ID 20230118061049.1006141-5-ajd@linux.ibm.com
State New
Headers
Series pSeries dynamic secure boot secvar interface + platform keyring loading |

Commit Message

Andrew Donnellan Jan. 18, 2023, 6:10 a.m. UTC 
  From: Russell Currey <ruscur@russell.cc>

The code that handles the format string in secvar-sysfs.c is entirely
OPAL specific, so create a new "format" op in secvar_operations to make
the secvar code more generic.  No functional change.

Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>

---

v2: Use sysfs_emit() instead of sprintf() (gregkh)

v3: Enforce format string size limit (ruscur)
---
 arch/powerpc/include/asm/secvar.h            |  3 +++
 arch/powerpc/kernel/secvar-sysfs.c           | 23 ++++--------------
 arch/powerpc/platforms/powernv/opal-secvar.c | 25 ++++++++++++++++++++
 3 files changed, 33 insertions(+), 18 deletions(-)

Comments

Nicholas Piggin Jan. 19, 2023, 1:02 a.m. UTC | #1 
On Wed Jan 18, 2023 at 4:10 PM AEST, Andrew Donnellan wrote:
> From: Russell Currey <ruscur@russell.cc>
>
> The code that handles the format string in secvar-sysfs.c is entirely
> OPAL specific, so create a new "format" op in secvar_operations to make
> the secvar code more generic.  No functional change.
>
> Signed-off-by: Russell Currey <ruscur@russell.cc>
> Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
>
> ---
>
> v2: Use sysfs_emit() instead of sprintf() (gregkh)
>
> v3: Enforce format string size limit (ruscur)
> ---
>  arch/powerpc/include/asm/secvar.h            |  3 +++
>  arch/powerpc/kernel/secvar-sysfs.c           | 23 ++++--------------
>  arch/powerpc/platforms/powernv/opal-secvar.c | 25 ++++++++++++++++++++
>  3 files changed, 33 insertions(+), 18 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/secvar.h b/arch/powerpc/include/asm/secvar.h
> index 07ba36f868a7..8b6475589120 100644
> --- a/arch/powerpc/include/asm/secvar.h
> +++ b/arch/powerpc/include/asm/secvar.h
> @@ -11,12 +11,15 @@
>  #include <linux/types.h>
>  #include <linux/errno.h>
>  
> +#define SECVAR_MAX_FORMAT_LEN	30 // max length of string returned by ->format()
> +
>  extern const struct secvar_operations *secvar_ops;
>  
>  struct secvar_operations {
>  	int (*get)(const char *key, u64 key_len, u8 *data, u64 *data_size);
>  	int (*get_next)(const char *key, u64 *key_len, u64 keybufsize);
>  	int (*set)(const char *key, u64 key_len, u8 *data, u64 data_size);
> +	ssize_t (*format)(char *buf);

Maybe pass the buf size as an argument here? Which is a bit less error
prone and more flexible than finding the right #define for it.

Thanks,
Nick
Nicholas Piggin Jan. 19, 2023, 1:17 a.m. UTC | #2 
On Wed Jan 18, 2023 at 4:10 PM AEST, Andrew Donnellan wrote:
> From: Russell Currey <ruscur@russell.cc>
>
> The code that handles the format string in secvar-sysfs.c is entirely
> OPAL specific, so create a new "format" op in secvar_operations to make
> the secvar code more generic.  No functional change.
>
> Signed-off-by: Russell Currey <ruscur@russell.cc>
> Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
>
> ---
>
> v2: Use sysfs_emit() instead of sprintf() (gregkh)
>
> v3: Enforce format string size limit (ruscur)
> ---
>  arch/powerpc/include/asm/secvar.h            |  3 +++
>  arch/powerpc/kernel/secvar-sysfs.c           | 23 ++++--------------
>  arch/powerpc/platforms/powernv/opal-secvar.c | 25 ++++++++++++++++++++
>  3 files changed, 33 insertions(+), 18 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/secvar.h b/arch/powerpc/include/asm/secvar.h
> index 07ba36f868a7..8b6475589120 100644
> --- a/arch/powerpc/include/asm/secvar.h
> +++ b/arch/powerpc/include/asm/secvar.h
> @@ -11,12 +11,15 @@
>  #include <linux/types.h>
>  #include <linux/errno.h>
>  
> +#define SECVAR_MAX_FORMAT_LEN	30 // max length of string returned by ->format()
> +
>  extern const struct secvar_operations *secvar_ops;
>  
>  struct secvar_operations {
>  	int (*get)(const char *key, u64 key_len, u8 *data, u64 *data_size);
>  	int (*get_next)(const char *key, u64 *key_len, u64 keybufsize);
>  	int (*set)(const char *key, u64 key_len, u8 *data, u64 data_size);
> +	ssize_t (*format)(char *buf);
>  };
>  
>  #ifdef CONFIG_PPC_SECURE_BOOT
> diff --git a/arch/powerpc/kernel/secvar-sysfs.c b/arch/powerpc/kernel/secvar-sysfs.c
> index 462cacc0ca60..d3858eedd72c 100644
> --- a/arch/powerpc/kernel/secvar-sysfs.c
> +++ b/arch/powerpc/kernel/secvar-sysfs.c
> @@ -21,26 +21,13 @@ static struct kset *secvar_kset;
>  static ssize_t format_show(struct kobject *kobj, struct kobj_attribute *attr,
>  			   char *buf)
>  {
> -	ssize_t rc = 0;
> -	struct device_node *node;
> -	const char *format;
> -
> -	node = of_find_compatible_node(NULL, NULL, "ibm,secvar-backend");
> -	if (!of_device_is_available(node)) {
> -		rc = -ENODEV;
> -		goto out;
> -	}
> +	char tmp[SECVAR_MAX_FORMAT_LEN];
> +	ssize_t len = secvar_ops->format(tmp);
>  
> -	rc = of_property_read_string(node, "format", &format);
> -	if (rc)
> -		goto out;
> +	if (len <= 0)
> +		return -EIO;

AFAIKS this does have a functional change, it loses the return value.
Why not return len if it is < 0, and -EIO if len == 0?

Thanks,
Nick
Russell Currey Jan. 20, 2023, 12:51 a.m. UTC | #3 
On Thu, 2023-01-19 at 11:17 +1000, Nicholas Piggin wrote:
> On Wed Jan 18, 2023 at 4:10 PM AEST, Andrew Donnellan wrote:
> > From: Russell Currey <ruscur@russell.cc>
> > 
> > The code that handles the format string in secvar-sysfs.c is
> > entirely
> > OPAL specific, so create a new "format" op in secvar_operations to
> > make
> > the secvar code more generic.  No functional change.
> > 
> > Signed-off-by: Russell Currey <ruscur@russell.cc>
> > Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
> > 
> > ---
> > 
> > v2: Use sysfs_emit() instead of sprintf() (gregkh)
> > 
> > v3: Enforce format string size limit (ruscur)
> > ---
> >  arch/powerpc/include/asm/secvar.h            |  3 +++
> >  arch/powerpc/kernel/secvar-sysfs.c           | 23 ++++------------
> > --
> >  arch/powerpc/platforms/powernv/opal-secvar.c | 25
> > ++++++++++++++++++++
> >  3 files changed, 33 insertions(+), 18 deletions(-)
> > 
> > diff --git a/arch/powerpc/include/asm/secvar.h
> > b/arch/powerpc/include/asm/secvar.h
> > index 07ba36f868a7..8b6475589120 100644
> > --- a/arch/powerpc/include/asm/secvar.h
> > +++ b/arch/powerpc/include/asm/secvar.h
> > @@ -11,12 +11,15 @@
> >  #include <linux/types.h>
> >  #include <linux/errno.h>
> >  
> > +#define SECVAR_MAX_FORMAT_LEN  30 // max length of string returned
> > by ->format()
> > +
> >  extern const struct secvar_operations *secvar_ops;
> >  
> >  struct secvar_operations {
> >         int (*get)(const char *key, u64 key_len, u8 *data, u64
> > *data_size);
> >         int (*get_next)(const char *key, u64 *key_len, u64
> > keybufsize);
> >         int (*set)(const char *key, u64 key_len, u8 *data, u64
> > data_size);
> > +       ssize_t (*format)(char *buf);
> >  };
> >  
> >  #ifdef CONFIG_PPC_SECURE_BOOT
> > diff --git a/arch/powerpc/kernel/secvar-sysfs.c
> > b/arch/powerpc/kernel/secvar-sysfs.c
> > index 462cacc0ca60..d3858eedd72c 100644
> > --- a/arch/powerpc/kernel/secvar-sysfs.c
> > +++ b/arch/powerpc/kernel/secvar-sysfs.c
> > @@ -21,26 +21,13 @@ static struct kset *secvar_kset;
> >  static ssize_t format_show(struct kobject *kobj, struct
> > kobj_attribute *attr,
> >                            char *buf)
> >  {
> > -       ssize_t rc = 0;
> > -       struct device_node *node;
> > -       const char *format;
> > -
> > -       node = of_find_compatible_node(NULL, NULL, "ibm,secvar-
> > backend");
> > -       if (!of_device_is_available(node)) {
> > -               rc = -ENODEV;
> > -               goto out;
> > -       }
> > +       char tmp[SECVAR_MAX_FORMAT_LEN];
> > +       ssize_t len = secvar_ops->format(tmp);
> >  
> > -       rc = of_property_read_string(node, "format", &format);
> > -       if (rc)
> > -               goto out;
> > +       if (len <= 0)
> > +               return -EIO;
> 
> AFAIKS this does have a functional change, it loses the return value.
> Why not return len if it is < 0, and -EIO if len == 0?

In v2 mpe suggested the following:

   I'm not sure you should pass that raw error back to sysfs. Some of
   the
   values could be confusing, eg. if you return -EINVAL it looks like a
   parameter to the read() syscall was invalid. Might be better to just
   return -EIO.
   
Following that advice, I don't think we should return something other
than -EIO, but we should at least pr_err() to document the error - this
isn't something that should ever fail.

> 
> Thanks,
> Nick
diff mbox series

Patch

diff --git a/arch/powerpc/include/asm/secvar.h b/arch/powerpc/include/asm/secvar.h
index 07ba36f868a7..8b6475589120 100644
--- a/arch/powerpc/include/asm/secvar.h
+++ b/arch/powerpc/include/asm/secvar.h
@@ -11,12 +11,15 @@ 
 #include <linux/types.h>
 #include <linux/errno.h>
 
+#define SECVAR_MAX_FORMAT_LEN	30 // max length of string returned by ->format()
+
 extern const struct secvar_operations *secvar_ops;
 
 struct secvar_operations {
 	int (*get)(const char *key, u64 key_len, u8 *data, u64 *data_size);
 	int (*get_next)(const char *key, u64 *key_len, u64 keybufsize);
 	int (*set)(const char *key, u64 key_len, u8 *data, u64 data_size);
+	ssize_t (*format)(char *buf);
 };
 
 #ifdef CONFIG_PPC_SECURE_BOOT
diff --git a/arch/powerpc/kernel/secvar-sysfs.c b/arch/powerpc/kernel/secvar-sysfs.c
index 462cacc0ca60..d3858eedd72c 100644
--- a/arch/powerpc/kernel/secvar-sysfs.c
+++ b/arch/powerpc/kernel/secvar-sysfs.c
@@ -21,26 +21,13 @@  static struct kset *secvar_kset;
 static ssize_t format_show(struct kobject *kobj, struct kobj_attribute *attr,
 			   char *buf)
 {
-	ssize_t rc = 0;
-	struct device_node *node;
-	const char *format;
-
-	node = of_find_compatible_node(NULL, NULL, "ibm,secvar-backend");
-	if (!of_device_is_available(node)) {
-		rc = -ENODEV;
-		goto out;
-	}
+	char tmp[SECVAR_MAX_FORMAT_LEN];
+	ssize_t len = secvar_ops->format(tmp);
 
-	rc = of_property_read_string(node, "format", &format);
-	if (rc)
-		goto out;
+	if (len <= 0)
+		return -EIO;
 
-	rc = sysfs_emit(buf, "%s\n", format);
-
-out:
-	of_node_put(node);
-
-	return rc;
+	return sysfs_emit(buf, "%s\n", tmp);
 }
 
 
diff --git a/arch/powerpc/platforms/powernv/opal-secvar.c b/arch/powerpc/platforms/powernv/opal-secvar.c
index ef89861569e0..623c6839e66c 100644
--- a/arch/powerpc/platforms/powernv/opal-secvar.c
+++ b/arch/powerpc/platforms/powernv/opal-secvar.c
@@ -98,10 +98,35 @@  static int opal_set_variable(const char *key, u64 ksize, u8 *data, u64 dsize)
 	return opal_status_to_err(rc);
 }
 
+static ssize_t opal_secvar_format(char *buf)
+{
+	ssize_t rc = 0;
+	struct device_node *node;
+	const char *format;
+
+	node = of_find_compatible_node(NULL, NULL, "ibm,secvar-backend");
+	if (!of_device_is_available(node)) {
+		rc = -ENODEV;
+		goto out;
+	}
+
+	rc = of_property_read_string(node, "format", &format);
+	if (rc)
+		goto out;
+
+	rc = snprintf(buf, SECVAR_MAX_FORMAT_LEN, "%s", format);
+
+out:
+	of_node_put(node);
+
+	return rc;
+}
+
 static const struct secvar_operations opal_secvar_ops = {
 	.get = opal_get_variable,
 	.get_next = opal_get_next_variable,
 	.set = opal_set_variable,
+	.format = opal_secvar_format,
 };
 
 static int opal_secvar_probe(struct platform_device *pdev)