linux-kernel - Re: [PATCH v4 19/39] unwind_user/sframe: Add support for reading .sframe contents

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: <20250204185121.jt5ylxsouqi5dyie@jpoimboe>
Date: Tue, 4 Feb 2025 10:51:21 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Jens Remus <jremus@...ux.ibm.com>
Cc: x86@...nel.org, Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	linux-kernel@...r.kernel.org, Indu Bhagat <indu.bhagat@...cle.com>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	linux-perf-users@...r.kernel.org, Mark Brown <broonie@...nel.org>,
	linux-toolchains@...r.kernel.org, Jordan Rome <jordalgo@...a.com>,
	Sam James <sam@...too.org>, linux-trace-kernel@...r.kernel.org,
	Andrii Nakryiko <andrii.nakryiko@...il.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Florian Weimer <fweimer@...hat.com>,
	Andy Lutomirski <luto@...nel.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Weinan Liu <wnliu@...gle.com>, Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>
Subject: Re: [PATCH v4 19/39] unwind_user/sframe: Add support for reading
 .sframe contents

On Thu, Jan 30, 2025 at 04:47:00PM +0100, Jens Remus wrote:
> On 22.01.2025 03:31, Josh Poimboeuf wrote:
> > +struct sframe_fre {
> > +	unsigned int	size;
> > +	s32		ip_off;
> 
> The IP offset (from function start) in the SFrame V2 FDE is unsigned:
> 
> u32 ip_off;

Indeed.

> > +#define __UNSAFE_GET_USER_INC(to, from, type, label)			\
> > +({									\
> > +	type __to;							\
> > +	unsafe_get_user(__to, (type __user *)from, label);		\
> > +	from += sizeof(__to);						\
> > +	to = (typeof(to))__to;							\
> > +})
> > +
> > +#define UNSAFE_GET_USER_INC(to, from, size, label)			\
> > +({									\
> > +	switch (size) {							\
> > +	case 1:								\
> > +		__UNSAFE_GET_USER_INC(to, from, u8, label);		\
> > +		break;							\
> > +	case 2:								\
> > +		__UNSAFE_GET_USER_INC(to, from, u16, label);		\
> > +		break;							\
> > +	case 4:								\
> > +		__UNSAFE_GET_USER_INC(to, from, u32, label);		\
> > +		break;							\
> > +	default:							\
> > +		return -EFAULT;						\
> > +	}								\
> > +})
> 
> This does not work for the signed SFrame fields, such as the FRE CFA,
> RA, and FP offsets, as it does not perform the required sign extension.
> One option would be to rename to UNSAFE_GET_USER_UNSIGNED_INC() and
> re-introduce UNSAFE_GET_USER_SIGNED_INC() using s8, s16, and s32.

See the following line in __UNSAFE_GET_USER_INC():

	to = (typeof(to))__to;

Does that not do the sign extension?

-- 
Josh