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Re: [PATCH] Fix readdir_r with long file names

From: Florian Weimer <fweimer at redhat dot com>
To: KOSAKI Motohiro <kosaki dot motohiro at gmail dot com>
Cc: "Carlos O'Donell" <carlos at redhat dot com>, libc-alpha <libc-alpha at sourceware dot org>
Date: Fri, 07 Jun 2013 13:47:16 +0200
Subject: Re: [PATCH] Fix readdir_r with long file names
References: <519220C7 dot 6050705 at redhat dot com> <20130516110136 dot GB11420 at spoyarek dot pnq dot redhat dot com> <5194CDEE dot 4020708 at redhat dot com> <20130516125029 dot GE11420 at spoyarek dot pnq dot redhat dot com> <5194D697 dot 8040106 at redhat dot com> <20130516130952 dot GA16952 at spoyarek dot pnq dot redhat dot com> <519B58EC dot 6060108 at redhat dot com> <51B0A2F9 dot 5060004 at redhat dot com> <51B0B39F dot 4060202 at redhat dot com> <51B0BD36 dot 3030202 at redhat dot com> <CAHGf_=r9Rz63pho+84ORk0a_oDyJSj-MCnZ56uPrT3L6sVEfeQ at mail dot gmail dot com> <51B0F1DD dot 5070901 at redhat dot com> <51B0F9D8 dot 7070203 at gmail dot com>

On 06/06/2013 11:06 PM, KOSAKI Motohiro wrote:

So, only broken applications may hit this? If so, do you really think
such
broken application checks return code correctly?


There's precedent for my approach in realpath, where we don't use
pathconf(path, _PC_PATH_MAX), either, but cap the path length at
PATH_MAX.


PATH_MAX is used VFS as hard coded limitations. So, I don't think any
Linux filesystem have a long path exceed PATH_MAX.

The canonical name of a file can be longer than PATH_MAX characters.This is probably true for all file systems supported by Linux (with thepossible exception of FAT). I don't think Linux enforces a directorynesting limit, but if it does, it is significantly larger than 4095divided by 255.

You cannot directly open such files, but it's possible to reach themwith (potentially multiple) calls to openat.


--
Florian Weimer / Red Hat Product Security Team

References:
- Re: [PATCH] Fix readdir_r with long file names
  - From: Florian Weimer
- Re: [PATCH] Fix readdir_r with long file names
  - From: Carlos O'Donell
- Re: [PATCH] Fix readdir_r with long file names
  - From: Florian Weimer
- Re: [PATCH] Fix readdir_r with long file names
  - From: KOSAKI Motohiro
- Re: [PATCH] Fix readdir_r with long file names
  - From: Florian Weimer
- Re: [PATCH] Fix readdir_r with long file names
  - From: KOSAKI Motohiro

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