[Coverity CID :208676] Overlapping buffer in memory copy in subsys/usb/class/mass_storage.c

[zephyrbot]

Static code scan issues found in file:

https://github.com/zephyrproject-rtos/zephyr/tree/23ace0e55681c02a81fb6b891f832aa356c85aab/subsys/usb/class/mass_storage.c#L744

Category: API usage errors
Function: thread_memory_write_done
Component: Other
CID: 208676

Details:

738     static void thread_memory_write_done(void)
739     {
740         u32_t size = defered_wr_sz;
741         size_t overflowed_len = (addr + size) % CONFIG_MASS_STORAGE_BULK_EP_MPS;
742    
743         if (overflowed_len) {
>>>     CID 208676:  API usage errors  (BUFFER_SIZE)
>>>     The source buffer "&page[512]" potentially overlaps with the destination buffer "page", which results in undefined behavior for "memcpy".
744             memcpy(page, &page[BLOCK_SIZE], overflowed_len);
745         }
746    
747         addr += size;
748         length -= size;
749         csw.DataResidue -= size;

Please fix or provide comments in coverity using the link:

https://scan9.coverity.com/reports.htm#v32951/p12996.

Note: This issue was created automatically. Priority was set based on classification
of the file affected and the impact field in coverity. Assignees were set using the CODEOWNERS file.

[jfischer-no]

CONFIG_MASS_STORAGE_BULK_EP_MPS is either 64 or 512 (for high speed), BLOCK_SIZE is 512, page buffer is BLOCK_SIZE+CONFIG_MASS_STORAGE_BULK_EP_MPS. It can not overlap, but memmove is better choice indeed.

I will fix int in following MSC cleanup patches.