PNP: ACPI: fix fortify warning

When compiling with gcc version 14.0.0 20231126 (experimental)
and CONFIG_FORTIFY_SOURCE=y, I've noticed the following:

In file included from ./include/linux/string.h:295,
from ./include/linux/bitmap.h:12,
from ./include/linux/cpumask.h:12,
from ./arch/x86/include/asm/paravirt.h:17,
from ./arch/x86/include/asm/cpuid.h:62,
from ./arch/x86/include/asm/processor.h:19,
from ./arch/x86/include/asm/cpufeature.h:5,
from ./arch/x86/include/asm/thread_info.h:53,
from ./include/linux/thread_info.h:60,
from ./arch/x86/include/asm/preempt.h:9,
from ./include/linux/preempt.h:79,
from ./include/linux/spinlock.h:56,
from ./include/linux/mmzone.h:8,
from ./include/linux/gfp.h:7,
from ./include/linux/slab.h:16,
from ./include/linux/resource_ext.h:11,
from ./include/linux/acpi.h:13,
from drivers/pnp/pnpacpi/rsparser.c:11:
In function 'fortify_memcpy_chk',
inlined from 'pnpacpi_parse_allocated_vendor' at drivers/pnp/pnpacpi/rsparser.c:158:3,
inlined from 'pnpacpi_allocated_resource' at drivers/pnp/pnpacpi/rsparser.c:249:3:
./include/linux/fortify-string.h:588:25: warning: call to '__read_overflow2_field'
declared with attribute warning: detected read beyond size of field (2nd parameter);
maybe use struct_group()? [-Wattribute-warning]
588 | __read_overflow2_field(q_size_field, size);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

According to the comments in include/linux/fortify-string.h, 'memcpy()',
'memmove()' and 'memset()' must not be used beyond individual struct
members to ensure that the compiler can enforce protection against
buffer overflows, and, IIUC, this also applies to partial copies from
the particular member ('vendor->byte_data' in this case). So it should
be better (and safer) to do both copies at once (and 'byte_data' of
'struct acpi_resource_vendor_typed' seems to be a good candidate for
'__counted_by(byte_length)' as well).

Signed-off-by: Dmitry Antipov <[e-mail]>
Reviewed-by: Kees Cook <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/pnp/pnpacpi/rsparser.c

···
 static void pnpacpi_parse_allocated_vendor(struct pnp_dev *dev,
 				    struct acpi_resource_vendor_typed *vendor)
 {
-	if (vendor_resource_matches(dev, vendor, &hp_ccsr_uuid, 16)) {
-		u64 start, length;
+	struct { u64 start, length; } range;
 
-		memcpy(&start, vendor->byte_data, sizeof(start));
-		memcpy(&length, vendor->byte_data + 8, sizeof(length));
-
-		pnp_add_mem_resource(dev, start, start + length - 1, 0);
+	if (vendor_resource_matches(dev, vendor, &hp_ccsr_uuid,
+				    sizeof(range))) {
+		memcpy(&range, vendor->byte_data, sizeof(range));
+		pnp_add_mem_resource(dev, range.start, range.start +
+				     range.length - 1, 0);
 	}
 }