selftests: watchdog: Validate optional file argument

The newly added optional file argument does not validate if the
file is indeed a watchdog, e.g.:

./watchdog-test  -f /dev/zero
Watchdog Ticking Away!

Fix it by confirming that the WDIOC_GETSUPPORT ioctl succeeds.

Fixes: a4864a33f56caa ("selftests: watchdog: Add optional file argument")
Reported-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Signed-off-by: George G. Davis <george_davis@mentor.com>
Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/tools/testing/selftests/watchdog/watchdog-test.c b/tools/testing/selftests/watchdog/watchdog-test.c
index afff120c7be6..6ed822dc2222 100644
--- a/tools/testing/selftests/watchdog/watchdog-test.c
+++ b/tools/testing/selftests/watchdog/watchdog-test.c
@@ -97,6 +97,7 @@ int main(int argc, char *argv[])
         int c;
         int oneshot = 0;
         char *file = "/dev/watchdog";
+        struct watchdog_info info;
 
         setbuf(stdout, NULL);
 
@@ -118,6 +119,16 @@ int main(int argc, char *argv[])
                 exit(-1);
         }
 
+        /*
+         * Validate that `file` is a watchdog device
+         */
+        ret = ioctl(fd, WDIOC_GETSUPPORT, &info);
+        if (ret) {
+                printf("WDIOC_GETSUPPORT error '%s'\n", strerror(errno));
+                close(fd);
+                exit(ret);
+        }
+
         optind = 0;
 
         while ((c = getopt_long(argc, argv, sopts, lopts, NULL)) != -1) {