Re: [dpdk-dev] [PATCH] bus/pci: fix driver name string manipulation

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

-----Original Message-----
> Date: Tue, 15 May 2018 18:19:19 +0800
> From: Andy Green <andy@warmcat.com>
> To: Jerin Jacob <jerin.jacob@caviumnetworks.com>, dev@dpdk.org
> CC: thomas@monjalon.net, ferruh.yigit@intel.com, Pablo de Lara
>  <pablo.de.lara.guarch@intel.com>
> Subject: Re: [dpdk-dev] [PATCH] bus/pci: fix driver name string manipulation
> User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
>  Thunderbird/52.7.0
> 
> 
> 
> On 05/15/2018 06:03 PM, Jerin Jacob wrote:
> > sizeof(dri_name) is 8B on 64Bit systems.The intended operation is coping
> > the string after '/' from the string `name`.
> > 
> > This bug is not letting to probe any device string >8B hence results in
> > the testpmd error("No ethernet devices found) on some PMDs.
> 
> You are right... but...
> 
> > Cc: Andy Green <andy@warmcat.com>
> > Cc: Pablo de Lara <pablo.de.lara.guarch@intel.com>
> > 
> > Fixes: fe5f777b538 ("bus/pci: replace strncpy by strlcpy")
> > 
> > Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> > ---
> >   drivers/bus/pci/linux/pci.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/bus/pci/linux/pci.c b/drivers/bus/pci/linux/pci.c
> > index a73ee49c2..cd45875b1 100644
> > --- a/drivers/bus/pci/linux/pci.c
> > +++ b/drivers/bus/pci/linux/pci.c
> > @@ -54,7 +54,7 @@ pci_get_kernel_driver_by_path(const char *filename, char *dri_name)
> >   	name = strrchr(path, '/');
> >   	if (name) {
> > -		strlcpy(dri_name, name + 1, sizeof(dri_name));
> > +		strlcpy(dri_name, name + 1, strlen(name));
> 
> ... this fix is no good.  The underlying problem is the length of dri_name
> is not getting passed into this function... it just doesn't know how much of
> dri_name is safe to use.  Telling it to use the strlen() of something
> unrelated is going to make buffer overflows possible.

In this case, already there is a check for following in the code. So it is fine
either way.

        path[count] = '\0';
        name = strrchr(path, '/');

> 
> I sent a patch to the list a few hours ago that amends this function to take
> the allocated length of dri_name, and sets the limit for the strlcpy() to
> that, so no matter what turns up in name it's not possible to blow past
> dri_name allocation.
> 
> [dpdk-dev] [PATCH] bus/pci: correct the earlier strlcpy conversion​

I am fine with taking any of the of the patch.  Please improve the patch subject
and bug description in case if you prefer to take your original patch.

> 
> -Andy
> 
> >   		return 0;
> >   	}
> >