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 <a...@linux.ibm.com>
Signed-off-by: Russell Currey <rus...@russell.cc>

---

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 <stef...@linux.ibm.com>

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