[RFC PATCH v1 1/3] x86/virt/seamldr: Allocate 'struct seamldr_params' after image validation

[Chao Gao <chao.gao@intel.com>]

'struct seamldr_params' is the in-memory ABI the kernel passes to P-SEAMLDR
to update the TDX module. It has a fixed size and is allocated before the
update image is validated.

To support larger TDX modules, the ABI was extended to let
'struct seamldr_params' link to extra pages. The number of extra pages
depends on the module page count, which can be trusted only after the image
header is validated.

Move the allocation after the image validation in init_seamldr_params(),
so a later change can allocate 'struct seamldr_params' and the extra
pages as one buffer. Rename the function to build_seamldr_params() since
it now allocates and returns a buffer rather than filling in one the
caller provides.

No functional change intended.

AI was used to review the code and workshop the logs. It suggested renaming
init_seamldr_params() and updating the comments above it and at its call
site.

Signed-off-by: Chao Gao <chao.gao@intel.com>
---
 arch/x86/virt/vmx/tdx/seamldr.c | 40 ++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 20 deletions(-)

diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index b1137ca6150d..3513fd28536a 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -157,13 +157,14 @@ static void populate_seamldr_params(struct seamldr_params *params,
 
 /*
  * @image points to a vmalloc()'d 'struct tdx_image'. Transform
- * it into @params which is the P-SEAMLDR ABI format.
+ * it into a newly allocated 'struct seamldr_params', which is
+ * the P-SEAMLDR ABI format.
  */
-static int init_seamldr_params(struct seamldr_params *params,
-			       const struct tdx_image *image,
-			       u32 image_len)
+static struct seamldr_params *build_seamldr_params(const struct tdx_image *image,
+						   u32 image_len)
 {
 	const struct tdx_image_header *header	= &image->header;
+	struct seamldr_params *params;
 
 	u32 sigstruct_len	= header->sigstruct_nr_pages * PAGE_SIZE;
 	u32 module_len		= header->module_nr_pages    * PAGE_SIZE;
@@ -178,25 +179,29 @@ static int init_seamldr_params(struct seamldr_params *params,
 
 	/* Check the calculated payload size against the image size. */
 	if (TDX_IMAGE_HEADER_SIZE + sigstruct_len + module_len != image_len)
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 
 	/* Reject unsupported tdx_image ABI versions. */
 	if (header->version != TDX_IMAGE_VERSION_2)
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 
 	if (header->sigstruct_nr_pages > SEAMLDR_MAX_NR_SIG_PAGES ||
 	    header->module_nr_pages    > SEAMLDR_MAX_NR_MODULE_PAGES)
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 
 	if (memcmp(header->signature, "TDX-BLOB", sizeof(header->signature)))
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 
 	if (memchr_inv(header->reserved, 0, sizeof(header->reserved)))
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
+
+	params = kzalloc_obj(*params);
+	if (!params)
+		return ERR_PTR(-ENOMEM);
 
 	populate_seamldr_params(params, sigstruct_start, header->sigstruct_nr_pages,
 					module_start,    header->module_nr_pages);
-	return 0;
+	return params;
 }
 
 /*
@@ -321,7 +326,7 @@ int seamldr_install_module(const u8 *data, u32 data_len)
 	int ret;
 
 	/*
-	 * init_seamldr_params() reads the header early.
+	 * build_seamldr_params() reads the header early.
 	 * Ensure there is enough data to do at least that.
 	 */
 	if (data_len < TDX_IMAGE_HEADER_SIZE)
@@ -329,14 +334,10 @@ int seamldr_install_module(const u8 *data, u32 data_len)
 
 	image = (const struct tdx_image *)data;
 
-	params = kzalloc_obj(*params);
-	if (!params)
-		return -ENOMEM;
-
-	/* Populate 'params' from 'image'. */
-	ret = init_seamldr_params(params, image, data_len);
-	if (ret)
-		goto out;
+	/* Build 'params' from 'image'. */
+	params = build_seamldr_params(image, data_len);
+	if (IS_ERR(params))
+		return PTR_ERR(params);
 
 	/* Ensure a stable set of online CPUs for the update process. */
 	cpus_read_lock();
@@ -345,7 +346,6 @@ int seamldr_install_module(const u8 *data, u32 data_len)
 				      cpu_online_mask);
 	cpus_read_unlock();
 
-out:
 	kfree(params);
 	return ret;
 }
-- 
2.52.0