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Re: /proc filesystem allows bypassing directory permissions on Linux

Why not?!?
File permissions allow everybody write access to the file.
The path via /proc to the file has been created when the initial path via /tmp was wide open. 
Closing the initial path via /tmp has no effect on the /proc path
And due to the actual file permissions the read-only fd can easily changed to read-write. 

        Marco

Sent from my iPhone 3G(s)

On 26 okt 2009, at 22:58, psz@xxxxxxxxxxxxxxxxx wrote:


Dear Casper and Dan,


If you can control<pid>, then clearly you have access the file anyway
simply by controlling it using a debugger.


Sorry, but no. The "attacker" has the file opened O_RDONLY, and cannot
"upgrade" that to O_RDWR.

Cheers, Paul

Paul Szabo   psz@xxxxxxxxxxxxxxxxx   http://www.maths.usyd.edu.au/u/psz/
School of Mathematics and Statistics University of Sydney Australia