Re: [PATCH v5 12/25] powerpc/secvar: Warn when PAGE_SIZE is smaller than max object size

[Stefan Berger]

On 1/31/23 01:39, Andrew Donnellan wrote:

Due to sysfs constraints, when writing to a variable, we can only handle
writes of up to PAGE_SIZE.

It's possible that the maximum object size is larger than PAGE_SIZE, in
which case, print a warning on boot so that the user is aware.

Signed-off-by: Andrew Donnellan 
Signed-off-by: Russell Currey 

---

v3: New patch (ajd)
---
  arch/powerpc/kernel/secvar-sysfs.c | 9 +
  1 file changed, 9 insertions(+)

diff --git a/arch/powerpc/kernel/secvar-sysfs.c 
b/arch/powerpc/kernel/secvar-sysfs.c
index 2cbc60b37e4e..9b6be63b7b36 100644
--- a/arch/powerpc/kernel/secvar-sysfs.c
+++ b/arch/powerpc/kernel/secvar-sysfs.c
@@ -223,6 +223,7 @@ static int secvar_sysfs_load_static(void)
  
  static int secvar_sysfs_init(void)

  {
+   u64 max_size;
int rc;
  
  	if (!secvar_ops) {

@@ -272,6 +273,14 @@ static int secvar_sysfs_init(void)
goto err;
}
  
+	// Due to sysfs limitations, we will only ever get a write buffer of

+   // up to 1 page in size. Print a warning if this is potentially going
+   // to cause problems, so that the user is aware.
+   secvar_ops->max_size(&max_size);
+   if (max_size > PAGE_SIZE)
+   pr_warn_ratelimited("PAGE_SIZE (%lu) is smaller than maximum object 
size (%llu), writes are limited to PAGE_SIZE\n",
+   PAGE_SIZE, max_size);
+
return 0;
  err:
kobject_put(secvar_kobj);


Reviewed-by: Stefan Berger 

[PATCH v5 12/25] powerpc/secvar: Warn when PAGE_SIZE is smaller than max object size

[Andrew Donnellan]

Due to sysfs constraints, when writing to a variable, we can only handle
writes of up to PAGE_SIZE.

It's possible that the maximum object size is larger than PAGE_SIZE, in
which case, print a warning on boot so that the user is aware.

Signed-off-by: Andrew Donnellan 
Signed-off-by: Russell Currey 

---

v3: New patch (ajd)
---
 arch/powerpc/kernel/secvar-sysfs.c | 9 +
 1 file changed, 9 insertions(+)

diff --git a/arch/powerpc/kernel/secvar-sysfs.c 
b/arch/powerpc/kernel/secvar-sysfs.c
index 2cbc60b37e4e..9b6be63b7b36 100644
--- a/arch/powerpc/kernel/secvar-sysfs.c
+++ b/arch/powerpc/kernel/secvar-sysfs.c
@@ -223,6 +223,7 @@ static int secvar_sysfs_load_static(void)
 
 static int secvar_sysfs_init(void)
 {
+   u64 max_size;
int rc;
 
if (!secvar_ops) {
@@ -272,6 +273,14 @@ static int secvar_sysfs_init(void)
goto err;
}
 
+   // Due to sysfs limitations, we will only ever get a write buffer of
+   // up to 1 page in size. Print a warning if this is potentially going
+   // to cause problems, so that the user is aware.
+   secvar_ops->max_size(&max_size);
+   if (max_size > PAGE_SIZE)
+   pr_warn_ratelimited("PAGE_SIZE (%lu) is smaller than maximum 
object size (%llu), writes are limited to PAGE_SIZE\n",
+   PAGE_SIZE, max_size);
+
return 0;
 err:
kobject_put(secvar_kobj);
-- 
2.39.1