Messages in this thread | | | From | Kyle Moffett <> | Subject | Re: [AppArmor 00/44] AppArmor security module overview | Date | Wed, 27 Jun 2007 06:58:46 -0400 |
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On Jun 26, 2007, at 22:24:03, John Johansen wrote: > other issues that have been raised are: > - the use of d_path to generate the pathname used for mediation when a > file is opened. > - Generating the pathname using a reverse walk is considered ugly
A little more than "ugly". In this basic concurrent rename() and path-lookup load:
mkdir -p /a/b/0 mkdir -p /a/b/2 mkdir -p /c touch /a/b/0/1
cd /a/b while true; mv 0/1 2/3; mv 2/3 0/1; done & cd / while true; do mv a/b c/d; mv c/d a/b; done & while true; do cat a/b/0/1 & done while true; do cat a/b/2/3 & done while true; do cat c/d/0/1 & done while true; do cat c/d/2/3 & done
I seem to recall you could actually end up racing and building a path to the file in those directories as "a/d/0/3" or some other path at which it never even remotely existed. I'd love to be wrong, but I can't help but see this problem in any reverse-pathname-generation proposal which gets the locking right.
Cheers, Kyle Moffett
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