[kbuild] drivers/gpu/drm/amd/amdkfd/kfd_crat.c:801:9: warning: Either the condition '!pcrat_image' is redundant or there is possible null pointer dereference: pcrat_image.

[Dan Carpenter]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  master
head:   4525c8781ec0701ce824e8bd379ae1b129e26568
commit: d0e63b343e575e8b74c185565b0d79a93494bcaa drm/amdkfd: Use kvmalloc instead of kmalloc for VCRAT
compiler: powerpc64le-linux-gcc (GCC) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>

cppcheck possible warnings: (new ones prefixed by >>, may not real problems)

   In file included from drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_crat.c:
>> drivers/gpu/drm/amd/amdkfd/kfd_crat.c:801:9: warning: Either the condition '!pcrat_image' is redundant or there is possible null pointer dereference: pcrat_image. [nullPointerRedundantCheck]
    memcpy(pcrat_image, crat_table, crat_table->length);
           ^
   drivers/gpu/drm/amd/amdkfd/kfd_crat.c:802:6: note: Assuming that condition '!pcrat_image' is not redundant
    if (!pcrat_image)
        ^
   drivers/gpu/drm/amd/amdkfd/kfd_crat.c:801:9: note: Null pointer dereference
    memcpy(pcrat_image, crat_table, crat_table->length);
           ^
   drivers/gpu/drm/amd/amdkfd/kfd_crat.c:405:32: warning: Shifting signed 32-bit value by 31 bits is undefined behaviour [shiftTooManyBitsSigned]
    if (props && (iolink->flags & CRAT_IOLINK_FLAGS_BI_DIRECTIONAL)) {
                                  ^
   drivers/gpu/drm/amd/amdkfd/kfd_crat.c:1112:26: warning: Shifting signed 32-bit value by 31 bits is undefined behaviour [shiftTooManyBitsSigned]
     sub_type_hdr->flags |= CRAT_IOLINK_FLAGS_BI_DIRECTIONAL;
                            ^
   drivers/gpu/drm/amd/amdkfd/kfd_crat.c:1146:11: warning: Shifting signed 32-bit value by 31 bits is undefined behaviour [shiftTooManyBitsSigned]
             CRAT_IOLINK_FLAGS_BI_DIRECTIONAL;
             ^
   drivers/gpu/drm/amd/amdkfd/kfd_crat.c:941:3: warning: Assignment of function parameter has no effect outside the function. Did you forget dereferencing it? [uselessAssignmentPtrArg]
     sub_type_hdr++;
     ^

vim +801 drivers/gpu/drm/amd/amdkfd/kfd_crat.c

8e05247d4c23ff1 Harish Kasiviswanathan 2017-12-08  772  int kfd_create_crat_image_acpi(void **crat_image, size_t *size)
174de876d6d02f7 Felix Kuehling         2017-12-08  773  {
174de876d6d02f7 Felix Kuehling         2017-12-08  774  	struct acpi_table_header *crat_table;
174de876d6d02f7 Felix Kuehling         2017-12-08  775  	acpi_status status;
8e05247d4c23ff1 Harish Kasiviswanathan 2017-12-08  776  	void *pcrat_image;
174de876d6d02f7 Felix Kuehling         2017-12-08  777  
8e05247d4c23ff1 Harish Kasiviswanathan 2017-12-08  778  	if (!crat_image)
174de876d6d02f7 Felix Kuehling         2017-12-08  779  		return -EINVAL;
174de876d6d02f7 Felix Kuehling         2017-12-08  780  
8e05247d4c23ff1 Harish Kasiviswanathan 2017-12-08  781  	*crat_image = NULL;
8e05247d4c23ff1 Harish Kasiviswanathan 2017-12-08  782  
8e05247d4c23ff1 Harish Kasiviswanathan 2017-12-08  783  	/* Fetch the CRAT table from ACPI */
174de876d6d02f7 Felix Kuehling         2017-12-08  784  	status = acpi_get_table(CRAT_SIGNATURE, 0, &crat_table);
174de876d6d02f7 Felix Kuehling         2017-12-08  785  	if (status == AE_NOT_FOUND) {
174de876d6d02f7 Felix Kuehling         2017-12-08  786  		pr_warn("CRAT table not found\n");
174de876d6d02f7 Felix Kuehling         2017-12-08  787  		return -ENODATA;
174de876d6d02f7 Felix Kuehling         2017-12-08  788  	} else if (ACPI_FAILURE(status)) {
174de876d6d02f7 Felix Kuehling         2017-12-08  789  		const char *err = acpi_format_exception(status);
174de876d6d02f7 Felix Kuehling         2017-12-08  790  
174de876d6d02f7 Felix Kuehling         2017-12-08  791  		pr_err("CRAT table error: %s\n", err);
174de876d6d02f7 Felix Kuehling         2017-12-08  792  		return -EINVAL;
174de876d6d02f7 Felix Kuehling         2017-12-08  793  	}
174de876d6d02f7 Felix Kuehling         2017-12-08  794  
6127896f4a27257 Huang Rui              2020-08-18  795  	if (kfd_ignore_crat()) {
ebcfd1e276207e4 Felix Kuehling         2017-12-08  796  		pr_info("CRAT table disabled by module option\n");
ebcfd1e276207e4 Felix Kuehling         2017-12-08  797  		return -ENODATA;
ebcfd1e276207e4 Felix Kuehling         2017-12-08  798  	}
ebcfd1e276207e4 Felix Kuehling         2017-12-08  799  
d0e63b343e575e8 Kent Russell           2020-09-18  800  	pcrat_image = kvmalloc(crat_table->length, GFP_KERNEL);
d0e63b343e575e8 Kent Russell           2020-09-18 @801  	memcpy(pcrat_image, crat_table, crat_table->length);
                                                                       ^^^^^^^^^^^
Dereferenced before the check for NULL

8e05247d4c23ff1 Harish Kasiviswanathan 2017-12-08  802  	if (!pcrat_image)
                                                                    ^^^^^^^^^^^^
Check.

8e05247d4c23ff1 Harish Kasiviswanathan 2017-12-08  803  		return -ENOMEM;
174de876d6d02f7 Felix Kuehling         2017-12-08  804  
8e05247d4c23ff1 Harish Kasiviswanathan 2017-12-08  805  	*crat_image = pcrat_image;
174de876d6d02f7 Felix Kuehling         2017-12-08  806  	*size = crat_table->length;
174de876d6d02f7 Felix Kuehling         2017-12-08  807  
174de876d6d02f7 Felix Kuehling         2017-12-08  808  	return 0;
174de876d6d02f7 Felix Kuehling         2017-12-08  809  }

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