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From: Bruce Richardson <bruce.richardson@intel.com>
To: Ferruh Yigit <ferruh.yigit@intel.com>
Cc: Kevin Laatz <kevin.laatz@intel.com>,
	dev@dpdk.org, stephen@networkplumber.org, stable@dpdk.org
Subject: Re: [dpdk-stable] [PATCH v2] net/ring: fix unchecked return value
Date: Mon, 12 Oct 2020 13:45:06 +0100
Message-ID: <20201012124506.GB565@bricha3-MOBL.ger.corp.intel.com> (raw)
In-Reply-To: <307b8070-977d-187f-c9c0-4b97477eda98@intel.com>

On Mon, Oct 12, 2020 at 12:57:11PM +0100, Ferruh Yigit wrote:
> On 10/1/2020 6:09 PM, Kevin Laatz wrote:
> > Add a check for the return value of the sscanf call in
> > parse_internal_args(), returning an error if we don't get the expected
> > result.
> > 
> > Coverity issue: 362049
> > Fixes: 96cb19521147 ("net/ring: use EAL APIs in PMD specific API")
> > Cc: stable@dpdk.org
> > 
> > Signed-off-by: Kevin Laatz <kevin.laatz@intel.com>
> > 
> > ---
> > v2: added consumed characters count check
> > ---
> >   drivers/net/ring/rte_eth_ring.c | 7 ++++++-
> >   1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ring/rte_eth_ring.c b/drivers/net/ring/rte_eth_ring.c
> > index 40fe1ca4ba..66367465fd 100644
> > --- a/drivers/net/ring/rte_eth_ring.c
> > +++ b/drivers/net/ring/rte_eth_ring.c
> > @@ -538,8 +538,13 @@ parse_internal_args(const char *key __rte_unused, const char *value,
> >   {
> >   	struct ring_internal_args **internal_args = data;
> >   	void *args;
> > +	int n;
> > -	sscanf(value, "%p", &args);
> > +	if (sscanf(value, "%p%n", &args, &n) != 1 || (size_t)n != strlen(value)) {
> 
> two small details,
> 
> 1- I see following note in the sscanf manual: https://linux.die.net/man/3/sscanf
> "
> The C standard says: "Execution of a %n directive does not increment the
> assignment count returned at the completion of execution" but the
> Corrigendum seems to contradict this. Probably it is wise not to make any
> assumptions on the effect of %n conversions on the return value.
> "
> 
> So what do you think checking return value as " == 0" ?
> 

Maybe in that copy of the man page but on my Ubuntu system there is no such
disclaimer, and I don't see it either on the kernel.org man page reference:

https://man7.org/linux/man-pages/man3/sscanf.3.html

That official man page reference clearly states that the behaviour is that
%n does not increase the reference count.


  reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-22 17:20 [dpdk-stable] [PATCH] " Kevin Laatz
2020-09-23  8:06 ` [dpdk-stable] [dpdk-dev] " David Marchand
2020-09-23  9:39   ` Bruce Richardson
2020-09-23  9:43     ` David Marchand
2020-09-23 10:04       ` Kevin Laatz
2020-09-23 10:25       ` Bruce Richardson
2020-09-25 12:43 ` [dpdk-stable] " Ferruh Yigit
2020-10-01 14:14   ` Kevin Laatz
2020-10-01 14:51     ` Ferruh Yigit
2020-10-01 17:09 ` [dpdk-stable] [PATCH v2] " Kevin Laatz
2020-10-12 11:57   ` Ferruh Yigit
2020-10-12 12:45     ` Bruce Richardson [this message]
2020-10-12 13:04       ` Ferruh Yigit
2020-10-12 13:11         ` Bruce Richardson
2020-10-13 13:07   ` [dpdk-stable] [PATCH v3] " Kevin Laatz
2020-10-13 17:23     ` Ferruh Yigit

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