bugtraq - Re: Re: readdir_r considered harmful

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <a36005b50511051753h47c56d33s662ed38e1a3c65fa@mail.gmail.com>
Date: Sat, 5 Nov 2005 17:53:42 -0800
From: Ulrich Drepper <drepper@...il.com>
To: "Casper.Dik@....com" <Casper.Dik@....com>
Cc: Ben Hutchings <ben@...adentplace.org.uk>, bugtraq@...urityfocus.com,
	full-disclosure@...ts.grok.org.uk
Subject: Re: Re: readdir_r considered harmful

On 11/5/05, Casper.Dik@....com <Casper.Dik@....com> wrote:
> Why not:
>
> 4. Require the readdir() implementation to use state local to dirp.
>
> I've never understood the rationale behind readdir_r;

Then you never really understood the implementation, seems.  Of course
all implementations keep the content of the directory as read with
getdents or so in the DIR descriptor.  But it is usually not the case
that the whole content fits into the buffer allocated.  One could, of
course, resize the buffer to fit the content of the directory read,
even if this means reserving hundreds or thousands of kBs.  But this
is not how most implementations work.

Instead implementations keep work similar to every buffered file I/O
operation.  But this means that buffer content is replaced.  If this
happens and some thread uses readdir() instead of readdir_r(), the
returned string pointer suddenly becomes invalid since it points to
memory which has been replaced.

Next time, before you make such comments, ask Don Cragun to explain
things to you.

_______________________________________________
Full-Disclosure - We believe in it.
Charter: http://lists.grok.org.uk/full-disclosure-charter.html
Hosted and sponsored by Secunia - http://secunia.com/