bugtraq - Re: Changes to the filesystem while find is running

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Message-ID: <000501c4d251$8ae73a50$86c8a8c0@MervaSBS2003.local>
Date: Wed, 24 Nov 2004 19:15:13 +0100
From: "Martin Buchholz" <Martin.Buchholz@....COM>
To: <kbo@....tiscali.de>
Cc: srevilak@...akeasy.net, James Youngman <bugtraq@...ession.spiral-arm.org>,
	parimiv@...haw.com, levon@...ementarian.org,
	bugtraq@...urityfocus.com, bug-findutils@....org
Subject: Re: Changes to the filesystem while find is running - comments?

Casper.Dik@....COM wrote:
>>I can see that that would be useful but it would fail to comply with
>>the POSIX standard, which specifies:
>>
>>         The find utility shall be able to descend to arbitrary
>>         depths in a file hierarchy and shall not fail due to path
>>         length limitations (unless a path operand specified by the
>>         application exceeds {PATH_MAX} requirements)
> 

> But PATH_MAX is limited and the number of file descriptors is perhaps
> not.
> 
> (On Solaris, PATH_MAX is 1024 so you require at most 512 file
> descriptors to keep the stack of directories: 512 is less than the
> default hard limit of 65536 file descriptors per process [S9, S8
> and before used 1024, still >> 512)

My reading of the above paragraph from the POSIX standard is
that find is required to be able to traverse arbitrary
depths, even when the resulting path length exceeds PATH_MAX.

On my Solaris 9 system, the default file descriptor limit
appears to be 256.

I am genuinely surprised that Solaris still has such a
relatively small PATH_MAX.  Linux has 4096.

Like other arbitrary system limits of its ilk, PATH_MAX
is evil, and is one of the more persuasive arguments for
getting rid of the C language and its fixed-size
stack-allocated buffers.

char path[PATH_MAX];  /* considered harmful */

Martin

> Casper