[PATCH 2/4] powerpc/pseries: Fix alignment of PLPKS structures and buffers

[Andrew Donnellan <ajd@linux.ibm.com>]

A number of structures and buffers passed to PKS hcalls have alignment
requirements, which could on occasion cause problems:

- Authorisation structures must be 16-byte aligned and must not cross a
  page boundary

- Label structures must not cross page coundaries

- Password output buffers must not cross page boundaries

Round up the allocations of these structures/buffers to the next power of
2 to make sure this happens.

Reported-by: Benjamin Gray <bgray@linux.ibm.com>
Fixes: 2454a7af0f2a ("powerpc/pseries: define driver for Platform KeyStore")
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
---
 arch/powerpc/platforms/pseries/plpks.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/plpks.c b/arch/powerpc/platforms/pseries/plpks.c
index cb93062e8223..8ccc91143370 100644
--- a/arch/powerpc/platforms/pseries/plpks.c
+++ b/arch/powerpc/platforms/pseries/plpks.c
@@ -126,7 +126,8 @@ static int plpks_gen_password(void)
 	u8 *password, consumer = PKS_OS_OWNER;
 	int rc;
 
-	password = kzalloc(maxpwsize, GFP_KERNEL);
+	// The password must not cross a page boundary, so we align to the next power of 2
+	password = kzalloc(roundup_pow_of_two(maxpwsize), GFP_KERNEL);
 	if (!password)
 		return -ENOMEM;
 
@@ -162,7 +163,9 @@ static struct plpks_auth *construct_auth(u8 consumer)
 	if (consumer > PKS_OS_OWNER)
 		return ERR_PTR(-EINVAL);
 
-	auth = kzalloc(struct_size(auth, password, maxpwsize), GFP_KERNEL);
+	// The auth structure must not cross a page boundary and must be
+	// 16 byte aligned. We align to the next largest power of 2
+	auth = kzalloc(roundup_pow_of_two(struct_size(auth, password, maxpwsize)), GFP_KERNEL);
 	if (!auth)
 		return ERR_PTR(-ENOMEM);
 
@@ -196,7 +199,8 @@ static struct label *construct_label(char *component, u8 varos, u8 *name,
 	if (component && slen > sizeof(label->attr.prefix))
 		return ERR_PTR(-EINVAL);
 
-	label = kzalloc(sizeof(*label), GFP_KERNEL);
+	// The label structure must not cross a page boundary, so we align to the next power of 2
+	label = kzalloc(roundup_pow_of_two(sizeof(*label)), GFP_KERNEL);
 	if (!label)
 		return ERR_PTR(-ENOMEM);
 
-- 
2.38.1