powerpc/pseries: Fix alignment of PLPKS structures and buffers

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 boundaries

- Password output buffers must not cross page boundaries

To ensure correct alignment, we adjust the allocation size of each of
these structures/buffers to be the closest power of 2 that is at least the
size of the structure/buffer (since kmalloc() guarantees that an
allocation of a power of 2 size will be aligned to at least that size).

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>
Reviewed-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230210080401.345462-3-ajd@linux.ibm.com

diff --git a/arch/powerpc/platforms/pseries/plpks.c b/arch/powerpc/platforms/pseries/plpks.c
index 9e85b6d..a01cf2f 100644 (file)
--- 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);