[syslinux] [PATCH] Updated udp.c to use real client ip and subnetmask values if on local subnet

[Patrick Masotta]

>>>
 Jeff, Patrick: Could you try my code from my github repo branch
 efi-multinic?  It's derived from Patrick's code and I finally see good
 responses with a VMware VM's e1000e NIC (never saw ANYTHING good from
 it until now).
 
 git://github.com/geneC/syslinux.git
 https://github.com/geneC/syslinux.git
 
 -- 
 -Gene
 <<<

Hi there
I think in the case of a particular driver that implements Pxebc but it does not implement UDPv4Sb/TCPv4Sb
(HP Elitebook 2560p/8460p) your patch crashes;

In that case the following for(;;) structure will never have a MAC match, then the
BS->OpenProtocol will never fail returning the needed "status != EFI_SUCCESS"
to avoid de-referencing an undefined pointer (sbp->CreateChild) in the next code line.

...
for (i = 0; i < nr_handles; i++) {
	    DevicePath = DevicePathFromHandle(handles[i]);
	    if (efi_get_MAC(DevicePath, &mac_2, PXE_MAC_LENGTH)
		    && memcmp(mac_1, mac_2, PXE_MAC_LENGTH) == 0) {
		 sb_handle = handles[i];
		status = uefi_call_wrapper(BS->OpenProtocol, 6, sb_handle,
					bguid, (void **)&sbp,
					image_handle, sb_handle,
					EFI_OPEN_PROTOCOL_GET_PROTOCOL);
		if (status == EFI_SUCCESS) {
		    mnpsb_handle = sb_handle;
		    break;
		}
	    }

	}

 }
    if (status != EFI_SUCCESS)
       goto free_binding;

    child = NULL;

    status = uefi_call_wrapper(sbp->CreateChild, 2, sbp, (EFI_HANDLE *)&child);  <<<< Potential crash here !

...


I think these changes would solve the thing.

...
-EFI_SERVICE_BINDING *sbp;
+EFI_SERVICE_BINDING *sbp =NULL;
...

-    if (status != EFI_SUCCESS)
+    if (status != EFI_SUCCESS || sbp != NULL)
       goto free_binding;
...


Please take a look;
BTW It's just only me or the adopted Linux kernel coding style makes following C code really a PITA ??

Best,
Patrick