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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <18586.43322.249846.130170@harpo.it.uu.se>
Date:	Thu, 7 Aug 2008 09:50:18 +0200
From:	Mikael Pettersson <mikpe@...uu.se>
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

Michael Davidson writes:
 > Prevent binaries from making system calls using other than one
 > of the "normal" system call interfaces for that binary type.
 > 
 > 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.
 > 
 > 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.

I asked Andi whether 64-bit processes are allowed to make 32-bit
syscalls on May 4 2007, and he stated that yes it's both allowed
and supposed to work. (The thread was cc:d to discuss@...-64.org.)

 > --- linux-2.6.26.2.orig/arch/x86/ia32/ia32entry.S	2008-08-06 09:19:01.000000000 -0700
 > +++ linux-2.6.26.2/arch/x86/ia32/ia32entry.S	2008-08-06 13:34:54.566992000 -0700
 > @@ -123,6 +123,8 @@
 >   	.quad 1b,ia32_badarg
 >   	.previous	
 >  	GET_THREAD_INFO(%r10)
 > +	testl  $_TIF_IA32,threadinfo_flags(%r10)
 > +	jz     ia32_bad_abi
 >  	orl    $TS_COMPAT,threadinfo_status(%r10)
 >  	testl  $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP),threadinfo_flags(%r10)
 >  	CFI_REMEMBER_STATE
 > @@ -230,6 +232,8 @@
 >  	.quad 1b,ia32_badarg
 >  	.previous	
 >  	GET_THREAD_INFO(%r10)
 > +	testl $_TIF_IA32,threadinfo_flags(%r10)
 > +	jz    ia32_bad_abi
 >  	orl   $TS_COMPAT,threadinfo_status(%r10)
 >  	testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP),threadinfo_flags(%r10)
 >  	CFI_REMEMBER_STATE
 > @@ -324,6 +328,8 @@
 >  	   this could be a problem. */
 >  	SAVE_ARGS 0,0,1
 >  	GET_THREAD_INFO(%r10)
 > +	testl $_TIF_IA32,threadinfo_flags(%r10)
 > +	jz    ia32_bad_abi
 >  	orl   $TS_COMPAT,threadinfo_status(%r10)
 >  	testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP),threadinfo_flags(%r10)
 >  	jnz ia32_tracesys

Your patch slows down all compat-mode syscalls.

/Mikael
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/