tools/xl: vcpu-pin: Skip global affinity when the hard affinity is not changed

After XSA-273, it is not possible to modify the vCPU soft affinity using
xl vcpu-pin without modifying the hard affinity. Instead the command
will crash.

42sh> gdb /usr/local/sbin/xl
(gdb) r vcpu-pin 0 0 - 10
[...]
Program received signal SIGSEGV, Segmentation fault.
[...]
(gdb) bt

This is happening because 'xl' will use NULL when an affinity doesn't
need to be modified. However, we will still try to apply the global
affinity in the this case.

As the hard affinity is not changed, then we don't need to apply the
global affinity. So skip it when hard is NULL.

Backport: 4.6+ # Any release with XSA-273
Fixes: aa67b97ed342 ("xl.conf: Add global affinity masks")
Reported-by: Pawel Wieczorkiewicz <wipawel@amazon.de>
Signed-off-by: Julien Grall <jgrall@amazon.com>
Acked-by: Wei Liu <wl@xen.org>

diff --git a/tools/xl/xl_vcpu.c b/tools/xl/xl_vcpu.c
index 9ff5354f749b5b3e79e060816f5314fd6001e39a..66877a57dee42acc00052ae93c780f72a17f620c 100644 (file)
--- a/tools/xl/xl_vcpu.c
+++ b/tools/xl/xl_vcpu.c
@@ -283,7 +283,7 @@ int main_vcpupin(int argc, char **argv)
     }
 
     /* Only hard affinity matters here */
-    if (!ignore_masks) {
+    if (!ignore_masks && hard) {
         libxl_dominfo dominfo;
 
         if (libxl_domain_info(ctx, &dominfo, domid)) {