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drm/amdgpu/smu10: Replace one-element array and use struct_size() helper 

The current codebase makes use of one-element arrays in the following
form:

struct something {
    int length;
    u8 data[1];
};

struct something *instance;

instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL);
instance->length = size;
memcpy(instance->data, source, size);

but the preferred mechanism to declare variable-length types such as
these ones is a flexible array member[1][2], introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on. So, replace
the one-element array with a flexible-array member.

Also, make use of the new struct_size() helper to properly calculate the
size of struct smu10_voltage_dependency_table.

This issue was found with the help of Coccinelle and, audited and fixed
_manually_.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Gustavo A. R. Silva 2020-05-19 17:55:45 -05:00 committed by Alex Deucher
parent 4cf7c42739
commit 94f2026bd8
2 changed files with 3 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c
View File

@ -410,12 +410,10 @@ static int smu10_get_clock_voltage_dependency_table(struct pp_hwmgr *hwmgr,
struct smu10_voltage_dependency_table **pptable,
uint32_t num_entry, const DpmClock_t *pclk_dependency_table)
{
uint32_t table_size, i;
uint32_t i;
struct smu10_voltage_dependency_table *ptable;
table_size = sizeof(uint32_t) + sizeof(struct smu10_voltage_dependency_table) * num_entry;
ptable = kzalloc(table_size, GFP_KERNEL);
ptable = kzalloc(struct_size(ptable, entries, num_entry), GFP_KERNEL);
if (NULL == ptable)
return -ENOMEM;

2
drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.h
View File

@ -192,7 +192,7 @@ struct smu10_clock_voltage_dependency_record {
struct smu10_voltage_dependency_table {
uint32_t count;
struct smu10_clock_voltage_dependency_record entries[1];
struct smu10_clock_voltage_dependency_record entries[];
};
struct smu10_clock_voltage_information {