From: Alex Elder <aelder@sgi.com>
To: Arkadiusz Miskiewicz <arekm@maven.pl>
Cc: xfs@oss.sgi.com
Subject: Re: xfs_metadump in never ending loop
Date: Sun, 03 Oct 2010 18:57:46 -0500 [thread overview]
Message-ID: <1286150266.4344.9.camel@doink> (raw)
In-Reply-To: <201010012136.47502.arekm@maven.pl>
On Fri, 2010-10-01 at 21:36 +0200, Arkadiusz Miskiewicz wrote:
> generate_obfuscated_name() in metadump.c can go into
> never ending loop for some file names. Reproducer below.
The reason it hangs is that the algorithm for computing
a name with the same hash value as the name is stuck with
a portion of the hash whose only possible result includes
the string "/" in it.
The hash for the file "R\323\257NE" is 0x3ab4b3740.
One step in the algorithm is this:
newname[namelen - 3] = (newhash >> 14) & 0x7f;
if (is_invalid_char(newname[namelen - 3]))
continue;
But the result of that is 0x2f, which is the '/'
character, which is illegal. So this algorithm
will try again indefinitely, never finding a file
name with a matching hash.
I am looking into this a bit more. Will report back
later, probably tomorrow.
-Alex
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next prev parent reply other threads:[~2010-10-04 0:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-01 19:36 xfs_metadump in never ending loop Arkadiusz Miskiewicz
2010-10-03 23:57 ` Alex Elder [this message]
2010-10-04 14:21 ` Alex Elder
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