linux-kernel - Re: [RFC PATCH 2/8] jump label v4 - x86: Introduce generic jump patching without stop

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]

Date:	Thu, 14 Jan 2010 10:39:09 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Jason Baron <jbaron@...hat.com>, linux-kernel@...r.kernel.org,
	mingo@...e.hu, hpa@...or.com, tglx@...utronix.de,
	andi@...stfloor.org, roland@...hat.com, rth@...hat.com,
	mhiramat@...hat.com, Arjan van de Ven <arjan@...radead.org>
Subject: Re: [RFC PATCH 2/8] jump label v4 - x86: Introduce generic jump
	patching without stop_machine

* Steven Rostedt (rostedt@...dmis.org) wrote:
> On Tue, 2010-01-12 at 11:26 -0500, Jason Baron wrote:
> 
> > +/**
> > + * text_poke_fixup() -- cross-modifying kernel text with fixup address.
> > + * @addr:	Modifying address.
> > + * @opcode:	New instruction.
> > + * @len:	length of modifying bytes.
> > + * @fixup:	Fixup address.
> > + *
> > + * Note: You must backup replaced instructions before calling this,
> > + * if you need to recover it.
> > + * Note: Must be called under text_mutex.
> > + */
> > +void *__kprobes text_poke_fixup(void *addr, const void *opcode, size_t len,
> > +				void *fixup)
> > +{
> > +	static const unsigned char int3_insn = BREAKPOINT_INSTRUCTION;
> > +	static const int int3_size = sizeof(int3_insn);
> > +
> > +	/* Replacing 1 byte can be done atomically. */
> > +	if (unlikely(len <= 1))
> > +		return text_poke(addr, opcode, len);
> 
> This part bothers me. The text_poke just writes over the text directly
> (using a separate mapping). But if that memory is in the pipeline of
> another CPU, I think this could cause a GPF.

It looks like we are thinking along the same lines.

I'm under the impression that I pointed out this exact same issue in the
previous round of review a few weeks ago. Does this submission reflect
the up-to-date state of this patch ?

Thanks,

Mathieu

> 
> -- Steve
> 
> > +
> > +	/* Preparing */
> > +	patch_fixup_addr = fixup;
> > +	wmb();
> > +	patch_fixup_from = (u8 *)addr + int3_size; /* IP address after int3 */
> > +
> > +	/* Cap by an int3 */
> > +	text_poke(addr, &int3_insn, int3_size);
> > +	sync_core_all();
> > +
> > +	/* Replace tail bytes */
> > +	text_poke((char *)addr + int3_size, (const char *)opcode + int3_size,
> > +		  len - int3_size);
> > +	sync_core_all();
> > +
> > +	/* Replace int3 with head byte */
> > +	text_poke(addr, opcode, int3_size);
> > +	sync_core_all();
> > +
> > +	/* Cleanup */
> > +	patch_fixup_from = NULL;
> > +	wmb();
> > +	return addr;
> > +}
> > +
> 

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
--
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/