On Tue, Sep 25, 2018 at 09:50:18AM -0600, Shuah Khan wrote:
Also can you run this test as normal user?
No. Must be run as root to open /dev/watchdog. When /dev/watchdog is opened, the WD is started and if not updated properly, the system will crash.
Hmm. I don't understand why the system would panic if non-root user can't open the device, at least in the context of this test.
fd = open("/dev/watchdog", O_WRONLY); if (fd == -1) { printf("Watchdog device not enabled.\n"); exit(-1); }Shouldn't it just exit based on the code above?
"cat /dev/watchdog" is one of my favorite ways to crash a system. :) :)
That doesn't sound great, if a non-root user can bring the system down!!
This got me concerned enough that I tried this with softdog. It behaved just the way I expected it.
cat /dev/watchdog cat: /dev/watchdog: Permission denied
Running the test as non-root does the following as per the current logic.
watchdog-test -b Watchdog device not enabled.
I think this logic could be improved to detect that a non-root user is running the test and print appropriate message.
However, I am not seeing the behavior you are describing that "cat /dev/watchdog" panics the syste. Did you mean running a root which is expected unless you terminate before the timeout? If you are seeing this as non-root user on you system, the watchdog driver could be suspect.
thanks, -- Shuah
Sorry, for misunderstanding. Let me rephrase:
When you asked if the test can be run as a normal user::
No. The test must be run as root to open /dev/watchdog as the permission on /dev/watchdog allow only root to open it. The reason that we only allow root to open /dev/watchdog is that it is trivial to crash the system. Just open /dev/watchdog and don't update the watchdog.
One of my favorite ways to crash the system is to as root "cat /dev/watchdog."