Re: [dpdk-dev] [PATCH 1/2] timer: fix null pointer dereference

["Carrillo, Erik G" <erik.g.carrillo@intel.com>]

> -----Original Message-----
> From: Bruce Richardson <bruce.richardson@intel.com>
> Sent: Tuesday, July 16, 2019 3:31 AM
> To: Carrillo, Erik G <erik.g.carrillo@intel.com>
> Cc: 'Stephen Hemminger' <stephen@networkplumber.org>;
> 'thomas@monjalon.net' <thomas@monjalon.net>; 'dev@dpdk.org'
> <dev@dpdk.org>
> Subject: Re: [dpdk-dev] [PATCH 1/2] timer: fix null pointer dereference
> 
> On Mon, Jul 15, 2019 at 07:48:09PM +0000, Carrillo, Erik G wrote:
> > > -----Original Message-----
> > > From: Carrillo, Erik G
> > > Sent: Monday, July 15, 2019 11:04 AM
> > > To: Stephen Hemminger <stephen@networkplumber.org>
> > > Cc: thomas@monjalon.net; dev@dpdk.org; stable@dpdk.org
> > > Subject: RE: [dpdk-dev] [PATCH 1/2] timer: fix null pointer
> > > dereference
> > >
> > > Hi Stephen,
> > >
> > > > -----Original Message-----
> > > > From: Stephen Hemminger <stephen@networkplumber.org>
> > > > Sent: Monday, July 15, 2019 10:49 AM
> > > > To: Carrillo, Erik G <erik.g.carrillo@intel.com>
> > > > Cc: thomas@monjalon.net; dev@dpdk.org; stable@dpdk.org
> > > > Subject: Re: [dpdk-dev] [PATCH 1/2] timer: fix null pointer
> > > > dereference
> > > >
> > > > On Mon, 15 Jul 2019 10:39:31 -0500 Erik Gabriel Carrillo
> > > > <erik.g.carrillo@intel.com> wrote:
> > > >
> > > > > If the timer subsystem is not initialized before
> > > > > rte_timer_manage (for
> > > > > example) is invoked, a pointer to a shared hugepage memory
> > > > > region will still be null and dereferenced when it is checked
> > > > > for validity; handle this case.
> > > > >
> > > > > Fixes: c0749f7096c7 ("timer: allow management in shared memory")
> > > > > Cc: stable@dpdk.org
> > > > >
> > > > > Signed-off-by: Erik Gabriel Carrillo <erik.g.carrillo@intel.com>
> > > >
> > > > I have mixed feelings about this patch.
> > > > Any calls to rte_timer before rte_timer_subsystem_init is not a valid
> usage.
> > > > Better to kill the application.
> > >
> > > Ok, that sounds like a better approach.  I'll update the patch and
> resubmit.
> > >
> >
> > I added a call to rte_exit() in the timer_data_valid() function for the case
> where the library is uninitialized, but checkpatches.sh issues the following
> warning:
> >
> > "Warning in /lib/librte_timer/rte_timer.c:
> > Using rte_panic/rte_exit"
> >
> > According to the comments in the script, we should refrain from new
> additions of rte_panic() and rte_exit() in the lib subtree.   In light of this,
> should we still proceed with this approach?  It does seem like it would be
> useful.
> >
> 
> I don't think we should ever put panics or exits in our library code, so I think
> the immediate choices are to either leave things as-is and allow app to crash
> for invalid use, or else catch the error and return a suitable error code to the
> user. I think I'd prefer the latter.
> 

In that case, I'd like to keep the current patch out for consideration.  It detects the error and enables the library APIs to return an error code to the user.

> However, given that the error condition is not having the timer subsystem
> initialized, is there the possibility of a third option to just go and initialize
> before continuing in the timer_manage() function?

It seems like this could work, but I'd like to hold off for more investigation.

Thanks,
Erik