[PATCH][next] nouveau/gsp: replace zero-length array with flex-array member and use __counted_by

[PATCH][next] nouveau/gsp: replace zero-length array with flex-array member and use __counted_by

[Gustavo A. R. Silva]

Fake flexible arrays (zero-length and one-element arrays) are deprecated,
and should be replaced by flexible-array members. So, replace
zero-length array with a flexible-array member in `struct
PACKED_REGISTRY_TABLE`.

Also annotate array `entries` with `__counted_by()` to prepare for the
coming implementation by GCC and Clang of the `__counted_by` attribute.
Flexible array members annotated with `__counted_by` can have their
accesses bounds-checked at run-time via `CONFIG_UBSAN_BOUNDS` (for array
indexing) and `CONFIG_FORTIFY_SOURCE` (for strcpy/memcpy-family functions).

This fixes multiple -Warray-bounds warnings:
drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1069:29: warning: array subscript 0 is outside array bounds of 'PACKED_REGISTRY_ENTRY[0]' [-Warray-bounds=]
drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1070:29: warning: array subscript 0 is outside array bounds of 'PACKED_REGISTRY_ENTRY[0]' [-Warray-bounds=]
drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1071:29: warning: array subscript 0 is outside array bounds of 'PACKED_REGISTRY_ENTRY[0]' [-Warray-bounds=]
drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1072:29: warning: array subscript 0 is outside array bounds of 'PACKED_REGISTRY_ENTRY[0]' [-Warray-bounds=]

While there, also make use of the struct_size() helper, and address
checkpatch.pl warning:
WARNING: please, no spaces at the start of a line

This results in no differences in binary output.

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 .../nvrm/535.113.01/nvidia/generated/g_os_nvoc.h   | 14 +++++++-------
 drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c     |  2 +-
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/include/nvrm/535.113.01/nvidia/generated/g_os_nvoc.h b/drivers/gpu/drm/nouveau/include/nvrm/535.113.01/nvidia/generated/g_os_nvoc.h
index 754c6af42f30..259b25c2ac6b 100644
--- a/drivers/gpu/drm/nouveau/include/nvrm/535.113.01/nvidia/generated/g_os_nvoc.h
+++ b/drivers/gpu/drm/nouveau/include/nvrm/535.113.01/nvidia/generated/g_os_nvoc.h
@@ -28,17 +28,17 @@
 
 typedef struct PACKED_REGISTRY_ENTRY
 {
-    NvU32                   nameOffset;
-    NvU8                    type;
-    NvU32                   data;
-    NvU32                   length;
+	NvU32                   nameOffset;
+	NvU8                    type;
+	NvU32                   data;
+	NvU32                   length;
 } PACKED_REGISTRY_ENTRY;
 
 typedef struct PACKED_REGISTRY_TABLE
 {
-    NvU32                   size;
-    NvU32                   numEntries;
-    PACKED_REGISTRY_ENTRY   entries[0];
+	NvU32                   size;
+	NvU32                   numEntries;
+	PACKED_REGISTRY_ENTRY   entries[] __counted_by(numEntries);
 } PACKED_REGISTRY_TABLE;
 
 #endif
diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c b/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c
index dc44f5c7833f..228335487af5 100644
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c
@@ -1048,7 +1048,7 @@ r535_gsp_rpc_set_registry(struct nvkm_gsp *gsp)
 	char *strings;
 	int str_offset;
 	int i;
-	size_t rpc_size = sizeof(*rpc) + sizeof(rpc->entries[0]) * NV_GSP_REG_NUM_ENTRIES;
+	size_t rpc_size = struct_size(rpc, entries, NV_GSP_REG_NUM_ENTRIES);
 
 	/* add strings + null terminator */
 	for (i = 0; i < NV_GSP_REG_NUM_ENTRIES; i++)
-- 
2.34.1

Re: [PATCH][next] nouveau/gsp: replace zero-length array with flex-array member and use __counted_by

[Kees Cook]

On Thu, Nov 16, 2023 at 12:11:43PM -0600, Gustavo A. R. Silva wrote:
> Fake flexible arrays (zero-length and one-element arrays) are deprecated,
> and should be replaced by flexible-array members. So, replace
> zero-length array with a flexible-array member in `struct
> PACKED_REGISTRY_TABLE`.
> 
> Also annotate array `entries` with `__counted_by()` to prepare for the
> coming implementation by GCC and Clang of the `__counted_by` attribute.
> Flexible array members annotated with `__counted_by` can have their
> accesses bounds-checked at run-time via `CONFIG_UBSAN_BOUNDS` (for array
> indexing) and `CONFIG_FORTIFY_SOURCE` (for strcpy/memcpy-family functions).
> 
> This fixes multiple -Warray-bounds warnings:
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1069:29: warning: array subscript 0 is outside array bounds of 'PACKED_REGISTRY_ENTRY[0]' [-Warray-bounds=]
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1070:29: warning: array subscript 0 is outside array bounds of 'PACKED_REGISTRY_ENTRY[0]' [-Warray-bounds=]
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1071:29: warning: array subscript 0 is outside array bounds of 'PACKED_REGISTRY_ENTRY[0]' [-Warray-bounds=]
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1072:29: warning: array subscript 0 is outside array bounds of 'PACKED_REGISTRY_ENTRY[0]' [-Warray-bounds=]
> 
> While there, also make use of the struct_size() helper, and address
> checkpatch.pl warning:
> WARNING: please, no spaces at the start of a line
> 
> This results in no differences in binary output.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Looks nice to me.

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

Re: [PATCH][next] nouveau/gsp: replace zero-length array with flex-array member and use __counted_by

[Danilo Krummrich]

Hi Gustavo,

On Thu, Nov 16, 2023 at 12:11:43PM -0600, Gustavo A. R. Silva wrote:
> Fake flexible arrays (zero-length and one-element arrays) are deprecated,
> and should be replaced by flexible-array members. So, replace
> zero-length array with a flexible-array member in `struct
> PACKED_REGISTRY_TABLE`.
> 
> Also annotate array `entries` with `__counted_by()` to prepare for the
> coming implementation by GCC and Clang of the `__counted_by` attribute.
> Flexible array members annotated with `__counted_by` can have their
> accesses bounds-checked at run-time via `CONFIG_UBSAN_BOUNDS` (for array
> indexing) and `CONFIG_FORTIFY_SOURCE` (for strcpy/memcpy-family functions).
> 
> This fixes multiple -Warray-bounds warnings:
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1069:29: warning: array subscript 0 is outside array bounds of 'PACKED_REGISTRY_ENTRY[0]' [-Warray-bounds=]
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1070:29: warning: array subscript 0 is outside array bounds of 'PACKED_REGISTRY_ENTRY[0]' [-Warray-bounds=]
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1071:29: warning: array subscript 0 is outside array bounds of 'PACKED_REGISTRY_ENTRY[0]' [-Warray-bounds=]
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1072:29: warning: array subscript 0 is outside array bounds of 'PACKED_REGISTRY_ENTRY[0]' [-Warray-bounds=]
> 
> While there, also make use of the struct_size() helper, and address
> checkpatch.pl warning:
> WARNING: please, no spaces at the start of a line
> 
> This results in no differences in binary output.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
>  .../nvrm/535.113.01/nvidia/generated/g_os_nvoc.h   | 14 +++++++-------
>  drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c     |  2 +-
>  2 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/include/nvrm/535.113.01/nvidia/generated/g_os_nvoc.h b/drivers/gpu/drm/nouveau/include/nvrm/535.113.01/nvidia/generated/g_os_nvoc.h
> index 754c6af42f30..259b25c2ac6b 100644
> --- a/drivers/gpu/drm/nouveau/include/nvrm/535.113.01/nvidia/generated/g_os_nvoc.h
> +++ b/drivers/gpu/drm/nouveau/include/nvrm/535.113.01/nvidia/generated/g_os_nvoc.h
> @@ -28,17 +28,17 @@
>  
>  typedef struct PACKED_REGISTRY_ENTRY
>  {
> -    NvU32                   nameOffset;
> -    NvU8                    type;
> -    NvU32                   data;
> -    NvU32                   length;
> +	NvU32                   nameOffset;
> +	NvU8                    type;
> +	NvU32                   data;
> +	NvU32                   length;
>  } PACKED_REGISTRY_ENTRY;
>  
>  typedef struct PACKED_REGISTRY_TABLE
>  {
> -    NvU32                   size;
> -    NvU32                   numEntries;
> -    PACKED_REGISTRY_ENTRY   entries[0];
> +	NvU32                   size;
> +	NvU32                   numEntries;
> +	PACKED_REGISTRY_ENTRY   entries[] __counted_by(numEntries);
>  } PACKED_REGISTRY_TABLE;

Thanks for the fix!

However, I have some concerns about changing those header files, since they're
just copied over from Nvidia's driver [1].

Once we add the header files for a new firmware revision, we'd potentially run
into the same issue, applying the same fix again.

As I already mentioned for Timur's patch [2], I'd prefer to get a fix upstream
(meaning [1] in this case). Of course, that's probably more up to Timur to tell
if this will work out.

If we can't get a fix upstream, I'd probably prefer to silence warning
elsewhere.

[1] https://github.com/NVIDIA/open-gpu-kernel-modules
[2] https://lore.kernel.org/all/20231107234726.854248-1-ttabi@nvidia.com/T/

>  
>  #endif
> diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c b/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c
> index dc44f5c7833f..228335487af5 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c
> @@ -1048,7 +1048,7 @@ r535_gsp_rpc_set_registry(struct nvkm_gsp *gsp)
>  	char *strings;
>  	int str_offset;
>  	int i;
> -	size_t rpc_size = sizeof(*rpc) + sizeof(rpc->entries[0]) * NV_GSP_REG_NUM_ENTRIES;
> +	size_t rpc_size = struct_size(rpc, entries, NV_GSP_REG_NUM_ENTRIES);
>  
>  	/* add strings + null terminator */
>  	for (i = 0; i < NV_GSP_REG_NUM_ENTRIES; i++)
> -- 
> 2.34.1
> 

Re: [Nouveau] [PATCH][next] nouveau/gsp: replace zero-length array with flex-array member and use __counted_by

[Timur Tabi]

On Thu, 2023-11-16 at 20:45 +0100, Danilo Krummrich wrote:
> As I already mentioned for Timur's patch [2], I'd prefer to get a fix
> upstream
> (meaning [1] in this case). Of course, that's probably more up to Timur to
> tell
> if this will work out.

Don't count on it.

Even if I did change [0] to [], I'm not going to be able to add the
"__counted_by(numEntries);" because that's just not something that our build
system uses.

And even then, I would need to change all [0] to [].  

You're not going to be able to use RM's header files as-is anyway in the
long term.  If we changed the layout of PACKED_REGISTRY_TABLE, we're not
going to create a PACKED_REGISTRY_TABLE2 and keep both around.  We're just
going to change PACKED_REGISTRY_TABLE and pretend the previous version never
existed.  You will then have to manually copy the new struct to your header
files and and maintain two versions yourself.

Re: [Nouveau] [PATCH][next] nouveau/gsp: replace zero-length array with flex-array member and use __counted_by

[Danilo Krummrich]

On 11/16/23 20:55, Timur Tabi wrote:
> On Thu, 2023-11-16 at 20:45 +0100, Danilo Krummrich wrote:
>> As I already mentioned for Timur's patch [2], I'd prefer to get a fix
>> upstream
>> (meaning [1] in this case). Of course, that's probably more up to Timur to
>> tell
>> if this will work out.
> 
> Don't count on it.

I see. Well, I think it's fine. Once we implement a decent abstraction we likely
don't need those header files in the kernel anymore.

@Gustavo, if you agree I will discard the indentation change when applying the
patch to keep the diff as small as possible.

- Danilo

> 
> Even if I did change [0] to [], I'm not going to be able to add the
> "__counted_by(numEntries);" because that's just not something that our build
> system uses.
> 
> And even then, I would need to change all [0] to [].
> 
> You're not going to be able to use RM's header files as-is anyway in the
> long term.  If we changed the layout of PACKED_REGISTRY_TABLE, we're not
> going to create a PACKED_REGISTRY_TABLE2 and keep both around.  We're just
> going to change PACKED_REGISTRY_TABLE and pretend the previous version never
> existed.  You will then have to manually copy the new struct to your header
> files and and maintain two versions yourself.
> 
> 
> 

Re: [Nouveau] [PATCH][next] nouveau/gsp: replace zero-length array with flex-array member and use __counted_by

[Gustavo A. R. Silva]

On 11/28/23 19:01, Danilo Krummrich wrote:
> On 11/16/23 20:55, Timur Tabi wrote:
>> On Thu, 2023-11-16 at 20:45 +0100, Danilo Krummrich wrote:
>>> As I already mentioned for Timur's patch [2], I'd prefer to get a fix
>>> upstream
>>> (meaning [1] in this case). Of course, that's probably more up to Timur to
>>> tell
>>> if this will work out.
>>
>> Don't count on it.
> 
> I see. Well, I think it's fine. Once we implement a decent abstraction we likely
> don't need those header files in the kernel anymore.
> 
> @Gustavo, if you agree I will discard the indentation change when applying the
> patch to keep the diff as small as possible.

No problem.

Thanks
--
Gustavo

Re: [Nouveau] [PATCH][next] nouveau/gsp: replace zero-length array with flex-array member and use __counted_by

[Danilo Krummrich]

On 11/29/23 02:06, Gustavo A. R. Silva wrote:
> 
> 
> On 11/28/23 19:01, Danilo Krummrich wrote:
>> On 11/16/23 20:55, Timur Tabi wrote:
>>> On Thu, 2023-11-16 at 20:45 +0100, Danilo Krummrich wrote:
>>>> As I already mentioned for Timur's patch [2], I'd prefer to get a fix
>>>> upstream
>>>> (meaning [1] in this case). Of course, that's probably more up to Timur to
>>>> tell
>>>> if this will work out.
>>>
>>> Don't count on it.
>>
>> I see. Well, I think it's fine. Once we implement a decent abstraction we likely
>> don't need those header files in the kernel anymore.
>>
>> @Gustavo, if you agree I will discard the indentation change when applying the
>> patch to keep the diff as small as possible.
> 
> No problem.

Applied to drm-misc-fixes.

> 
> Thanks
> -- 
> Gustavo
> 
>