linux-kernel - Re: [PATCH 5/8] scsi: lpfc: change snprintf to scnprintf for possible overflow

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Date:   Wed, 20 Mar 2019 18:39:51 +0100
From:   Greg KH <greg@...ah.com>
To:     James Smart <james.smart@...adcom.com>
Cc:     Kees Cook <keescook@...omium.org>, Willy Tarreau <w@....eu>,
        Silvio Cesare <silvio.cesare@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Dick Kennedy <dick.kennedy@...adcom.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Will Deacon <will.deacon@....com>
Subject: Re: [PATCH 5/8] scsi: lpfc: change snprintf to scnprintf for
 possible overflow

On Tue, Jan 15, 2019 at 02:41:17PM -0800, James Smart wrote:
> 
> On 1/14/2019 5:15 PM, Kees Cook wrote:
> > On Sat, Jan 12, 2019 at 7:29 AM Willy Tarreau<w@....eu>  wrote:
> > > From: Silvio Cesare<silvio.cesare@...il.com>
> > > 
> > > Change snprintf to scnprintf. There are generally two cases where using
> > > snprintf causes problems.
> > > 
> > > 1) Uses of size += snprintf(buf, SIZE - size, fmt, ...)
> > > In this case, if snprintf would have written more characters than what the
> > > buffer size (SIZE) is, then size will end up larger than SIZE. In later
> > > uses of snprintf, SIZE - size will result in a negative number, leading
> > > to problems. Note that size might already be too large by using
> > > size = snprintf before the code reaches a case of size += snprintf.
> > > 
> > > 2) If size is ultimately used as a length parameter for a copy back to user
> > > space, then it will potentially allow for a buffer overflow and information
> > > disclosure when size is greater than SIZE. When the size is used to index
> > > the buffer directly, we can have memory corruption. This also means when
> > > size = snprintf... is used, it may also cause problems since size may become
> > > large.  Copying to userspace is mitigated by the HARDENED_USERCOPY kernel
> > > configuration.
> > > 
> > > The solution to these issues is to use scnprintf which returns the number of
> > > characters actually written to the buffer, so the size variable will never
> > > exceed SIZE.
> > > 
> > > Signed-off-by: Silvio Cesare<silvio.cesare@...il.com>
> > > Cc: James Smart<james.smart@...adcom.com>
> > > Cc: Dick Kennedy<dick.kennedy@...adcom.com>
> > > Cc: Dan Carpenter<dan.carpenter@...cle.com>
> > > Cc: Kees Cook<keescook@...omium.org>
> > > Cc: Will Deacon<will.deacon@....com>
> > > Cc: Greg KH<greg@...ah.com>
> > > Signed-off-by: Willy Tarreau<w@....eu>
> > I think this needs Cc: stable.
> > 
> > Reviewed-by: Kees Cook<keescook@...omium.org>
> > 
> > -Kees
> > 
> 
> 
> Reviewed-by:  James Smart <james.smart@...adcom.com>

What ever happened to this patch?  Did it get dropped somehow?

thanks,

greg k-h