tools/xl: vcpu-pin: Skip global affinity when the hard affinity is not changed
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Message ID 20200430110051.8965-1-julien@xen.org
State New
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  • tools/xl: vcpu-pin: Skip global affinity when the hard affinity is not changed
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Commit Message

Julien Grall April 30, 2020, 11 a.m. UTC
From: Julien Grall <jgrall@amazon.com>

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>
---
 tools/xl/xl_vcpu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Wei Liu May 1, 2020, 12:15 p.m. UTC | #1
On Thu, Apr 30, 2020 at 12:00:51PM +0100, Julien Grall wrote:
> From: Julien Grall <jgrall@amazon.com>
> 
> 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>

> ---
>  tools/xl/xl_vcpu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/xl/xl_vcpu.c b/tools/xl/xl_vcpu.c
> index 9ff5354f749b..66877a57dee4 100644
> --- 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)) {
> -- 
> 2.17.1
>

Patch
diff mbox series

diff --git a/tools/xl/xl_vcpu.c b/tools/xl/xl_vcpu.c
index 9ff5354f749b..66877a57dee4 100644
--- 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)) {