Hello Bob Moore,
The patch c13085e519e8: "ACPICA: Resource Mgr: Prevent infinite loops
in resource walks" from Mar 8, 2013 is not beautiful. My static checker
complains about the loop because:
"drivers/acpi/acpica/rscalc.c:197 acpi_rs_get_aml_length()
warn: 'resource' can't be NULL."
drivers/acpi/acpica/rscalc.c
195 /* Traverse entire list of internal resource descriptors */
196
197 while (resource) {
^^^^^^^^
My static checker is wrong because we use the -fno-strict-overflow to
prevent GCC from optimizing this check away. But we are looping over
a list of pointers until our pointer wraps to NULL. In other words we
loop over all the 2**64 - 1 addresses until we wrap to NULL or we find
something with an invalid type or something with ->length zero.
I assume the last element in the list always has length zero? If so
then we could replace "while (resource)" with "while (resource->length)"
198
199 /* Validate the descriptor type */
200
201 if (resource->type > ACPI_RESOURCE_TYPE_MAX) {
202 return_ACPI_STATUS(AE_AML_INVALID_RESOURCE_TYPE);
203 }
204
205 /* Sanity check the length. It must not be zero, or we loop forever */
206
207 if (!resource->length) {
208 return_ACPI_STATUS(AE_AML_BAD_RESOURCE_LENGTH);
209 }
210
211 /* Get the base size of the (external stream) resource descriptor */
212
regards,
dan carpenter
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