Re: [PATCH] lib/cmdline: init parse result memeory

[Adrien Mazarguil <adrien.mazarguil@6wind.com>]

On Thu, Dec 07, 2017 at 03:35:24PM +0000, Xueming(Steven) Li wrote:
> 
> > -----Original Message-----
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Xueming(Steven) Li
> > Sent: Thursday, December 7, 2017 11:05 PM
> > To: Olivier MATZ <olivier.matz@6wind.com>
> > Cc: dev@dpdk.org
> > Subject: Re: [dpdk-dev] [PATCH] lib/cmdline: init parse result memeory
> > 
> > Hi Olivier,
> > 
> > > -----Original Message-----
> > > From: Olivier MATZ [mailto:olivier.matz@6wind.com]
> > > Sent: Thursday, December 7, 2017 10:48 PM
> > > To: Xueming(Steven) Li <xuemingl@mellanox.com>
> > > Cc: dev@dpdk.org
> > > Subject: Re: [PATCH] lib/cmdline: init parse result memeory
> > >
> > > On Wed, Nov 15, 2017 at 11:54:02PM +0800, Xueming Li wrote:
> > > > Initialize binary result memory before parsing to avoid garbage in
> > > > parsing result.
> > > >
> > > > Signed-off-by: Xueming Li <xuemingl@mellanox.com>
> > > > ---
> > > >  lib/librte_cmdline/cmdline_parse.c | 2 ++
> > > >  1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/lib/librte_cmdline/cmdline_parse.c
> > > > b/lib/librte_cmdline/cmdline_parse.c
> > > > index 3e12ee54f..9124758f1 100644
> > > > --- a/lib/librte_cmdline/cmdline_parse.c
> > > > +++ b/lib/librte_cmdline/cmdline_parse.c
> > > > @@ -267,6 +267,8 @@ cmdline_parse(struct cmdline *cl, const char * buf)
> > > >  	if (!cl || !buf)
> > > >  		return CMDLINE_PARSE_BAD_ARGS;
> > > >
> > > > +	memset(tmp_result.buf, 0, sizeof(tmp_result.buf));
> > > > +
> > > >  	ctx = cl->ctx;
> > > >
> > > >  	/*
> > >
> > >
> > > Did you see an issue (a bug or a crash) without the memset()?
> > > Or is it to avoid filling unused fields in the parsed struct?
> > Yes, I'm using same struct for some similar commands, have to avoid
> > filling unused fields.
> > 
> > >
> > > I'm not sure if your patch is enough: cmdline_parse() calls
> > > match_inst() for each registered command. If a command partially
> > > matches (only the first tokens), the buffer is modified. So the next
> > > one will start with a dirty buffer.
> > >
> > > I suggest to put the memset() in match_inst() instead. Something like
> > this:
> > >
> > > 	if (resbuf != NULL)
> > > 		memset(resbuf, 0, resbuf_size);
> > >
> > >
> > > It will reset the buffer before using it.
> > It was there for performance concern, since the buffer could be tainted,
> > I'll upload a new version according to your suggestion, appreciate your
> > suggestion.
> Rte_flow CLI seems to be relying on modified buffer, add Adrien:
> testpmd> flow create 0 ingress pattern eth  / ipv4 / udp / vxlan / end actions rss queues 1 2 end level 1 / mark id 0x123456  / end
> Caught error type 2 (flow rule (handle)): no valid action

While the flow command relies on the contents of this buffer when parsing
tokens, it doesn't expect it to be maintained across match_inst() calls.

In fact another issue prevents Olivier's suggestion from working.
Commit 9b3fbb051d2e ("cmdline: fix parsing") is supposed prevent further
match_inst() calls after the right inst is found but doesn't break
cmdline_parse()'s loop; subsequent iterations clear the result buffer.

Here's a suggestion to try:

 diff --git a/lib/librte_cmdline/cmdline_parse.c b/lib/librte_cmdline/cmdline_parse.c
 index 3e12ee5..e967410 100644
 --- a/lib/librte_cmdline/cmdline_parse.c
 +++ b/lib/librte_cmdline/cmdline_parse.c
 @@ -338,8 +338,8 @@ cmdline_parse(struct cmdline *cl, const char * buf)
                                         err = CMDLINE_PARSE_AMBIGUOUS;
                                         f=NULL;
                                         debug_printf("Ambiguous cmd\n");
 -                                       break;
                                 }
 +                               break;
                         }
                 }

-- 
Adrien Mazarguil
6WIND