[xen master] tools/libxenevtchn: check xenevtchn_open() flags for not supported bits

[patchbot@xxxxxxx]

commit f7918dc8f94c1640ba18341d7812f5c461d064ce
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Fri Jan 15 09:29:36 2021 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Jan 15 11:44:47 2021 +0000

    tools/libxenevtchn: check xenevtchn_open() flags for not supported bits
    
    Refuse a call of xenevtchn_open() with unsupported bits in flags being
    set.
    
    This will change behavior for callers passing junk in flags today,
    but those would otherwise get probably unwanted side effects when the
    flags they specify today get any meaning. So checking flags is the
    right thing to do.
    
    Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 tools/libs/evtchn/core.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/tools/libs/evtchn/core.c b/tools/libs/evtchn/core.c
index 72d92e28bf..79990d0027 100644
--- a/tools/libs/evtchn/core.c
+++ b/tools/libs/evtchn/core.c
@@ -13,6 +13,7 @@
  * License along with this library; If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <errno.h>
 #include <unistd.h>
 #include <stdlib.h>
 
@@ -31,9 +32,16 @@ static int all_restrict_cb(Xentoolcore__Active_Handle *ah, 
domid_t domid)
 
 xenevtchn_handle *xenevtchn_open(xentoollog_logger *logger, unsigned int flags)
 {
-    xenevtchn_handle *xce = malloc(sizeof(*xce));
+    xenevtchn_handle *xce;
     int rc;
 
+    if ( flags )
+    {
+        errno = EINVAL;
+        return NULL;
+    }
+
+    xce = malloc(sizeof(*xce));
     if ( !xce )
         return NULL;
 
--
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