full-disclosure - Re: new class of printf issue: int overflow

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Message-Id: <200701111620.15421.tom@electric-sheep.org>
Date: Thu, 11 Jan 2007 16:20:15 +0100
From: Thomas <tom@...ctric-sheep.org>
To: full-disclosure@...ts.grok.org.uk
Subject: Re: new class of printf issue: int overflow


> > > But that got me thinking.  *printf return an int, and it's supposed to
> > > be the number of chars written.  So a typical idiom is
> > > 
> > >   size_t memory_needed=snprintf(NULL,0,format_string,...);
> > >   char* ptr=malloc(memory_needed+1);
> > >   sprintf(ptr,format_string,...);
> > This is nothing new.
> > It is documented in the man-page and in the libc sources.
> 
> What is documented in what man page?  Neither the Linux man page nor the
> SUSv3 say anything about integer overflows and what sprintf should
> return in that case.
> 
> And, uh, glibc does not handle the issue, so the libc code does not
> document anything either.

returning a negative value.
 
> Felix

-- 
Tom <tom@...ctric-sheep.org>
fingerprint = F055 43E5 1F3C 4F4F 9182  CD59 DBC6 111A 8516 8DBF

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