Unsafe memory access in testpmd

Unsafe memory access in testpmd

[Stephen Hemminger]

Noticed that test-pmd is using a signal handler to exit.
And that signal handle clears a flag "f_quit".
But that variable is updated without atomic and is not volatile.

Simple fix to use atomic, would fix that part.
But the signal_handler is calling a bunch of functions that are not
safe in a signal handler.

The signal handler in testpmd should only be doing atomic
update of f_quit.  All the cleanup logic needs to be moved to
a place where thread is an safe state, like after exiting
the forwarding loop in main thread.

The problem is that testpmd has grown in complexity and not
sure if this won't break other things.

RE: Unsafe memory access in testpmd

[Ruifeng Wang]

> -----Original Message-----
> From: Stephen Hemminger <stephen@networkplumber.org>
> Sent: Friday, October 14, 2022 7:39 AM
> To: Ruifeng Wang <Ruifeng.Wang@arm.com>; Honnappa Nagarahalli
> <Honnappa.Nagarahalli@arm.com>
> Cc: dev@dpdk.org
> Subject: Unsafe memory access in testpmd
> 
> Noticed that test-pmd is using a signal handler to exit.
> And that signal handle clears a flag "f_quit".
> But that variable is updated without atomic and is not volatile.
> 
> Simple fix to use atomic, would fix that part.
> But the signal_handler is calling a bunch of functions that are not safe in a signal
> handler.
> 
> The signal handler in testpmd should only be doing atomic update of f_quit.  All the
> cleanup logic needs to be moved to a place where thread is an safe state, like after
> exiting the forwarding loop in main thread.
Agree. 

> 
> The problem is that testpmd has grown in complexity and not sure if this won't break other
> things.
We can propose patches. Review and testing from the community are expected to cover as many cases as possible.