[PATCH] drm/radeon: Prefer kcalloc over open coded arithmetic

[PATCH] drm/radeon: Prefer kcalloc over open coded arithmetic

[Len Baker]

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

So, refactor the code a bit to use the purpose specific kcalloc()
function instead of the calculated size argument in the kzalloc()
function.

[1] https://www.kernel.org/doc/html/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker <len.baker@gmx.com>
---
 drivers/gpu/drm/radeon/r600_dpm.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/radeon/r600_dpm.c b/drivers/gpu/drm/radeon/r600_dpm.c
index 35b77c944701..fd4226b99862 100644
--- a/drivers/gpu/drm/radeon/r600_dpm.c
+++ b/drivers/gpu/drm/radeon/r600_dpm.c
@@ -820,12 +820,12 @@ union fan_info {
 static int r600_parse_clk_voltage_dep_table(struct radeon_clock_voltage_dependency_table *radeon_table,
 					    ATOM_PPLIB_Clock_Voltage_Dependency_Table *atom_table)
 {
-	u32 size = atom_table->ucNumEntries *
-		sizeof(struct radeon_clock_voltage_dependency_entry);
 	int i;
 	ATOM_PPLIB_Clock_Voltage_Dependency_Record *entry;

-	radeon_table->entries = kzalloc(size, GFP_KERNEL);
+	radeon_table->entries = kcalloc(atom_table->ucNumEntries,
+					sizeof(struct radeon_clock_voltage_dependency_entry),
+					GFP_KERNEL);
 	if (!radeon_table->entries)
 		return -ENOMEM;

--
2.25.1

Re: [PATCH] drm/radeon: Prefer kcalloc over open coded arithmetic

[Alex Deucher]

Applied.  Thanks!

Alex

On Sat, Sep 4, 2021 at 11:41 AM Len Baker <len.baker@gmx.com> wrote:
>
> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> and Conventions" documentation [1], size calculations (especially
> multiplication) should not be performed in memory allocator (or similar)
> function arguments due to the risk of them overflowing. This could lead
> to values wrapping around and a smaller allocation being made than the
> caller was expecting. Using those allocations could lead to linear
> overflows of heap memory and other misbehaviors.
>
> So, refactor the code a bit to use the purpose specific kcalloc()
> function instead of the calculated size argument in the kzalloc()
> function.
>
> [1] https://www.kernel.org/doc/html/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
>
> Signed-off-by: Len Baker <len.baker@gmx.com>
> ---
>  drivers/gpu/drm/radeon/r600_dpm.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/r600_dpm.c b/drivers/gpu/drm/radeon/r600_dpm.c
> index 35b77c944701..fd4226b99862 100644
> --- a/drivers/gpu/drm/radeon/r600_dpm.c
> +++ b/drivers/gpu/drm/radeon/r600_dpm.c
> @@ -820,12 +820,12 @@ union fan_info {
>  static int r600_parse_clk_voltage_dep_table(struct radeon_clock_voltage_dependency_table *radeon_table,
>                                             ATOM_PPLIB_Clock_Voltage_Dependency_Table *atom_table)
>  {
> -       u32 size = atom_table->ucNumEntries *
> -               sizeof(struct radeon_clock_voltage_dependency_entry);
>         int i;
>         ATOM_PPLIB_Clock_Voltage_Dependency_Record *entry;
>
> -       radeon_table->entries = kzalloc(size, GFP_KERNEL);
> +       radeon_table->entries = kcalloc(atom_table->ucNumEntries,
> +                                       sizeof(struct radeon_clock_voltage_dependency_entry),
> +                                       GFP_KERNEL);
>         if (!radeon_table->entries)
>                 return -ENOMEM;
>
> --
> 2.25.1
>