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[v4,11/24] powerpc/secvar: Warn when PAGE_SIZE is smaller than max object size

Message ID 20230120074306.1326298-12-ajd@linux.ibm.com (mailing list archive)
State New
Headers show
Series pSeries dynamic secure boot secvar interface + platform keyring loading | expand

Commit Message

Andrew Donnellan Jan. 20, 2023, 7:42 a.m. UTC
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 <ajd@linux.ibm.com>
Signed-off-by: Russell Currey <ruscur@russell.cc>


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


diff --git a/arch/powerpc/kernel/secvar-sysfs.c b/arch/powerpc/kernel/secvar-sysfs.c
index e1d4c70dd327..6dd9b4f6f87c 100644
--- a/arch/powerpc/kernel/secvar-sysfs.c
+++ b/arch/powerpc/kernel/secvar-sysfs.c
@@ -221,6 +221,7 @@  static int secvar_sysfs_load_static(void)
 static int secvar_sysfs_init(void)
+	u64 max_size;
 	int rc;
 	if (!secvar_ops) {
@@ -270,6 +271,14 @@  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;