linux-kernel - Re: [PATCH] x86: prevent binaries from making system calls using the wrong syscall interface

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Message-ID: <20080807111539.2895a2c4@lxorguk.ukuu.org.uk>
Date:	Thu, 7 Aug 2008 11:15:39 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	md@...gle.com (Michael Davidson)
Cc:	mingo@...hat.com, tglx@...utronix.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: prevent binaries from making system calls using
 the wrong syscall interface

> Currently there is nothing to prevent 64 bit binaries from
> attempting to make system calls using the 32 bit system call
> interfaces and vice versa.

What about applications that choose to do this
- Test tools
- Tools where certain interfaces are only available 32bit ?

> Since the 32 bit and 64 bit system call numbers are different
> this means that a binary could attempt to obfuscate which system
> calls it was actually making by using the "wrong" system call
> interface. In particular, the call to audit_syscall_entry()
> relies on checking the TIF_IA32 flag to determine whether it is
> dealing with a 32 or 64 bit system call without regard to the
> actual type of system call that was made.While this specific issue
> could be addressed by checking the TS_COMPAT flag in threadinfo_status
> it seems preferable to simply disallow this situation altogether.

That is a significant change of kernel ABI considering it exists just to
wallpaper over crappy audit tools.

I'm definitely against that approach.

Alan
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