linux-kernel - Re: [RFC 1/1] seccomp: Add bitmask of allowed system calls.

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Message-ID: <20090515195644.GA1377@ucw.cz>
Date:	Fri, 15 May 2009 21:56:44 +0200
From:	Pavel Machek <pavel@....cz>
To:	Adam Langley <agl@...gle.com>
Cc:	linux-kernel@...r.kernel.org, markus@...gle.com
Subject: Re: [RFC 1/1] seccomp: Add bitmask of allowed system calls.

Hi!

> Briefly, it adds a second seccomp mode (2) where one uploads a bitmask.
> Syscall n is allowed if, and only if, bit n is true in the bitmask. If n
> is beyond the range of the bitmask, the syscall is denied.
> 
> If prctl is allowed by the bitmask, then a process may switch to mode 1,
> or may set a new bitmask iff the new bitmask is a subset of the current
> one. (Possibly moving to mode 1 should only be allowed if read, write,
> sigreturn, exit are in the currently allowed set.)
> 
> If a process forks/clones, the child inherits the seccomp state of the
> parent. (And hopefully I'm managing the memory correctly here.)

If you allow setuid exec here, you have added a security hole. Deny
setuid() to sendmail and have fun...

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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