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Date:   Wed, 5 Apr 2023 17:36:02 -0700
From:   Dan Williams <dan.j.williams@intel.com>
To:     "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Linux ACPI <linux-acpi@vger.kernel.org>
CC:     LKML <linux-kernel@vger.kernel.org>,
        Bob Moore <robert.moore@intel.com>,
        Kees Cook <kees@outflux.net>,
        Dan Williams <dan.j.williams@intel.com>
Subject: RE: [PATCH 22/32] ACPICA: actbl2: Replace 1-element arrays with
 flexible arrays
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Rafael J. Wysocki wrote:
> From: Kees Cook <kees@outflux.net>
> 
> ACPICA commit 44f1af0664599e87bebc3a1260692baa27b2f264
> 
> Similar to "Replace one-element array with flexible-array", replace the
> 1-element array with a proper flexible array member as defined by C99.
> 
> This allows the code to operate without tripping compile-time and run-
> time bounds checkers (e.g. via __builtin_object_size(), -fsanitize=bounds,
> and/or -fstrict-flex-arrays=3).
> 
> The sizeof() uses with struct acpi_nfit_flush_address and struct
> acpi_nfit_smbios have been adjusted to drop the open-coded subtraction
> of the trailing single element. The result is no binary differences in
> .text nor .data sections.
> 
> Link: https://github.com/acpica/acpica/commit/44f1af06
> Signed-off-by: Bob Moore <robert.moore@intel.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

This one needs the following folded in to pass my tests.

Feel free to fold and add:

Co-developed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com> 

-- >8 --
diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
index 981f8b0f595d..85d9d67e38a4 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -894,7 +894,7 @@ static size_t sizeof_flush(struct acpi_nfit_flush_address *flush)
 {
 	if (flush->header.length < sizeof(*flush))
 		return 0;
-	return sizeof(*flush) + sizeof(u64) * (flush->hint_count - 1);
+	return struct_size(flush, hint_address, flush->hint_count);
 }
 
 static bool add_flush(struct acpi_nfit_desc *acpi_desc,
diff --git a/tools/testing/nvdimm/test/nfit.c b/tools/testing/nvdimm/test/nfit.c
index c75abb497a1a..745c4a27bc35 100644
--- a/tools/testing/nvdimm/test/nfit.c
+++ b/tools/testing/nvdimm/test/nfit.c
@@ -1878,14 +1878,14 @@ static size_t sizeof_spa(struct acpi_nfit_system_address *spa)
 static int nfit_test0_alloc(struct nfit_test *t)
 {
 	struct acpi_nfit_system_address *spa = NULL;
+	struct acpi_nfit_flush_address *flush;
 	size_t nfit_size = sizeof_spa(spa) * NUM_SPA
 			+ sizeof(struct acpi_nfit_memory_map) * NUM_MEM
 			+ sizeof(struct acpi_nfit_control_region) * NUM_DCR
 			+ offsetof(struct acpi_nfit_control_region,
 					window_size) * NUM_DCR
 			+ sizeof(struct acpi_nfit_data_region) * NUM_BDW
-			+ (sizeof(struct acpi_nfit_flush_address)
-					+ sizeof(u64) * NUM_HINTS) * NUM_DCR
+			+ struct_size(flush, hint_address, NUM_HINTS) * NUM_DCR
 			+ sizeof(struct acpi_nfit_capabilities);
 	int i;