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Re: Possible bug in readlink, canonicalize fails.

From: Andreas Schwab
Subject: Re: Possible bug in readlink, canonicalize fails.
Date: Fri, 21 Sep 2007 15:49:10 +0200
User-agent: Gnus/5.110006 (No Gnus v0.6) Emacs/22.1 (gnu/linux)

mpb <address@hidden> writes:

> # Create 3 symbolic links inside those directories.
> ln -s a1/a2         /tmp/a0/a2
> ln -s /tmp/a0/a2/b3 /tmp/c0/b3
> ln -s /tmp/a0/a2/a3/a4/a5 /tmp/c0/b3/b4/a5

The problem is that we are crossing the /tmp/a0/a2 symlink twice, so
canonicalize_filename_mode thinks this is a loop.  But in fact the
reference comes from different symlink expansions, and the second one
uses a different way through the filesystem.  Due to the way cycle_check
works this testcase only works when the offending symlink is the second,
fourth, eighth, ... one encountered.  The kernel can cope because it
only errors out after a fixed number of symlink expansions, independent
of the actual nodes crossed.


Andreas Schwab, SuSE Labs, address@hidden
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
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