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Message-ID: <a66056cf-570c-4875-b5cf-c51e2bc488d9@intel.com>
Date: Fri, 14 Feb 2025 15:04:52 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>,
Alison Schofield <alison.schofield@...el.com>,
Dan Williams <dan.j.williams@...el.com>,
Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>,
"Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>
Cc: nvdimm@...ts.linux.dev, linux-acpi@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2][next] UAPI: ndctl / acpi: intel: Avoid multiple
-Wflex-array-member-not-at-end warnings
On 2/13/25 5:53 PM, Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
>
> So, in order to avoid ending up with flexible-array members in the
> middle of other structs, we use the `__struct_group()` helper to
> separate the flexible array from the rest of the members in the
> flexible structure. We then use the newly created tagged `struct
> nd_cmd_pkg_hdr` to replace the type of the objects causing trouble:
> `pkg` in multiple structs.
>
> Below is the before-and-after changes of the memory layout in `struct
> nd_cmd_pkg`. This to illustrate that the use of `__struct_group()`
> doesn't alter the layout, ensuring that user space remains unaffected.
>
> Before changes:
> struct nd_cmd_pkg {
> __u64 nd_family; /* 0 8 */
> __u64 nd_command; /* 8 8 */
> __u32 nd_size_in; /* 16 4 */
> __u32 nd_size_out; /* 20 4 */
> __u32 nd_reserved2[9]; /* 24 36 */
> __u32 nd_fw_size; /* 60 4 */
> /* --- cacheline 1 boundary (64 bytes) --- */
> unsigned char nd_payload[]; /* 64 0 */
>
> /* size: 64, cachelines: 1, members: 7 */
> };
>
> After changes:
> struct nd_cmd_pkg {
> union {
> struct {
> __u64 nd_family; /* 0 8 */
> __u64 nd_command; /* 8 8 */
> __u32 nd_size_in; /* 16 4 */
> __u32 nd_size_out; /* 20 4 */
> __u32 nd_reserved2[9]; /* 24 36 */
> __u32 nd_fw_size; /* 60 4 */
> }; /* 0 64 */
> struct nd_cmd_pkg_hdr __hdr; /* 0 64 */
> }; /* 0 64 */
> /* --- cacheline 1 boundary (64 bytes) --- */
> unsigned char nd_payload[]; /* 64 0 */
>
> /* size: 64, cachelines: 1, members: 2 */
> };
>
> It's also worth mentioning that all members of the struct can still be
> accessed directly, for example instance->nd_family, instance->nd_command,
> and so on.
>
> So, with these changes, fix 12 of the following warnings:
>
> drivers/acpi/nfit/intel.c:692:35: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> ---
> Changes in v2:
> - Show changes in UAPI first. (Alison)
> - Update changelog text --add more information about _struct_group()
> changes. (Alison)
>
> v1:
> - Link: https://lore.kernel.org/linux-hardening/Z618ILbAR8YAvTkd@kspp/
>
> include/uapi/linux/ndctl.h | 15 +++++++++------
> drivers/acpi/nfit/intel.c | 24 ++++++++++++------------
> 2 files changed, 21 insertions(+), 18 deletions(-)
>
> diff --git a/include/uapi/linux/ndctl.h b/include/uapi/linux/ndctl.h
> index 73516e263627..34c11644d5d7 100644
> --- a/include/uapi/linux/ndctl.h
> +++ b/include/uapi/linux/ndctl.h
> @@ -227,12 +227,15 @@ enum ars_masks {
> */
>
> struct nd_cmd_pkg {
> - __u64 nd_family; /* family of commands */
> - __u64 nd_command;
> - __u32 nd_size_in; /* INPUT: size of input args */
> - __u32 nd_size_out; /* INPUT: size of payload */
> - __u32 nd_reserved2[9]; /* reserved must be zero */
> - __u32 nd_fw_size; /* OUTPUT: size fw wants to return */
> + /* New members MUST be added within the __struct_group() macro below. */
> + __struct_group(nd_cmd_pkg_hdr, __hdr, /* no attrs */,
> + __u64 nd_family; /* family of commands */
> + __u64 nd_command;
> + __u32 nd_size_in; /* INPUT: size of input args */
> + __u32 nd_size_out; /* INPUT: size of payload */
> + __u32 nd_reserved2[9]; /* reserved must be zero */
> + __u32 nd_fw_size; /* OUTPUT: size fw wants to return */
> + );
> unsigned char nd_payload[]; /* Contents of call */
> };
>
> diff --git a/drivers/acpi/nfit/intel.c b/drivers/acpi/nfit/intel.c
> index 3902759abcba..fe561ce0ddec 100644
> --- a/drivers/acpi/nfit/intel.c
> +++ b/drivers/acpi/nfit/intel.c
> @@ -56,7 +56,7 @@ static unsigned long intel_security_flags(struct nvdimm *nvdimm,
> struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
> unsigned long security_flags = 0;
> struct {
> - struct nd_cmd_pkg pkg;
> + struct nd_cmd_pkg_hdr pkg;
> struct nd_intel_get_security_state cmd;
> } nd_cmd = {
> .pkg = {
> @@ -121,7 +121,7 @@ static int intel_security_freeze(struct nvdimm *nvdimm)
> {
> struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
> struct {
> - struct nd_cmd_pkg pkg;
> + struct nd_cmd_pkg_hdr pkg;
> struct nd_intel_freeze_lock cmd;
> } nd_cmd = {
> .pkg = {
> @@ -154,7 +154,7 @@ static int intel_security_change_key(struct nvdimm *nvdimm,
> NVDIMM_INTEL_SET_MASTER_PASSPHRASE :
> NVDIMM_INTEL_SET_PASSPHRASE;
> struct {
> - struct nd_cmd_pkg pkg;
> + struct nd_cmd_pkg_hdr pkg;
> struct nd_intel_set_passphrase cmd;
> } nd_cmd = {
> .pkg = {
> @@ -196,7 +196,7 @@ static int __maybe_unused intel_security_unlock(struct nvdimm *nvdimm,
> {
> struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
> struct {
> - struct nd_cmd_pkg pkg;
> + struct nd_cmd_pkg_hdr pkg;
> struct nd_intel_unlock_unit cmd;
> } nd_cmd = {
> .pkg = {
> @@ -235,7 +235,7 @@ static int intel_security_disable(struct nvdimm *nvdimm,
> int rc;
> struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
> struct {
> - struct nd_cmd_pkg pkg;
> + struct nd_cmd_pkg_hdr pkg;
> struct nd_intel_disable_passphrase cmd;
> } nd_cmd = {
> .pkg = {
> @@ -278,7 +278,7 @@ static int __maybe_unused intel_security_erase(struct nvdimm *nvdimm,
> unsigned int cmd = ptype == NVDIMM_MASTER ?
> NVDIMM_INTEL_MASTER_SECURE_ERASE : NVDIMM_INTEL_SECURE_ERASE;
> struct {
> - struct nd_cmd_pkg pkg;
> + struct nd_cmd_pkg_hdr pkg;
> struct nd_intel_secure_erase cmd;
> } nd_cmd = {
> .pkg = {
> @@ -319,7 +319,7 @@ static int __maybe_unused intel_security_query_overwrite(struct nvdimm *nvdimm)
> int rc;
> struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
> struct {
> - struct nd_cmd_pkg pkg;
> + struct nd_cmd_pkg_hdr pkg;
> struct nd_intel_query_overwrite cmd;
> } nd_cmd = {
> .pkg = {
> @@ -355,7 +355,7 @@ static int __maybe_unused intel_security_overwrite(struct nvdimm *nvdimm,
> int rc;
> struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
> struct {
> - struct nd_cmd_pkg pkg;
> + struct nd_cmd_pkg_hdr pkg;
> struct nd_intel_overwrite cmd;
> } nd_cmd = {
> .pkg = {
> @@ -408,7 +408,7 @@ static int intel_bus_fwa_businfo(struct nvdimm_bus_descriptor *nd_desc,
> struct nd_intel_bus_fw_activate_businfo *info)
> {
> struct {
> - struct nd_cmd_pkg pkg;
> + struct nd_cmd_pkg_hdr pkg;
> struct nd_intel_bus_fw_activate_businfo cmd;
> } nd_cmd = {
> .pkg = {
> @@ -519,7 +519,7 @@ static int intel_bus_fwa_activate(struct nvdimm_bus_descriptor *nd_desc)
> {
> struct acpi_nfit_desc *acpi_desc = to_acpi_desc(nd_desc);
> struct {
> - struct nd_cmd_pkg pkg;
> + struct nd_cmd_pkg_hdr pkg;
> struct nd_intel_bus_fw_activate cmd;
> } nd_cmd = {
> .pkg = {
> @@ -583,7 +583,7 @@ static int intel_fwa_dimminfo(struct nvdimm *nvdimm,
> struct nd_intel_fw_activate_dimminfo *info)
> {
> struct {
> - struct nd_cmd_pkg pkg;
> + struct nd_cmd_pkg_hdr pkg;
> struct nd_intel_fw_activate_dimminfo cmd;
> } nd_cmd = {
> .pkg = {
> @@ -689,7 +689,7 @@ static int intel_fwa_arm(struct nvdimm *nvdimm, enum nvdimm_fwa_trigger arm)
> struct nfit_mem *nfit_mem = nvdimm_provider_data(nvdimm);
> struct acpi_nfit_desc *acpi_desc = nfit_mem->acpi_desc;
> struct {
> - struct nd_cmd_pkg pkg;
> + struct nd_cmd_pkg_hdr pkg;
> struct nd_intel_fw_activate_arm cmd;
> } nd_cmd = {
> .pkg = {
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