linux-kernel - Re: [PATCH 4/6] hw_breakpoint: Factor out __modify_user_hw

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:   Mon, 27 Nov 2017 17:46:39 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        David Ahern <dsahern@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Milind Chabbi <chabbi.milind@...il.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Hari Bathini <hbathini@...ux.vnet.ibm.com>,
        Jin Yao <yao.jin@...ux.intel.com>,
        Kan Liang <kan.liang@...el.com>,
        Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
        Oleg Nesterov <onestero@...hat.com>,
        Will Deacon <will.deacon@....com>
Subject: Re: [PATCH 4/6] hw_breakpoint: Factor out
 __modify_user_hw_breakpoint function

On Mon, Nov 27, 2017 at 05:21:31PM +0100, Jiri Olsa wrote:
> +static int __modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
> +{
> +	u64 old_addr = bp->attr.bp_addr;
> +	u64 old_len  = bp->attr.bp_len;
> +	int old_type = bp->attr.bp_type;
> +	bool modify  = attr->bp_type != old_type;
> +	int err = 0;
> +
> +	bp->attr.bp_addr = attr->bp_addr;
> +	bp->attr.bp_type = attr->bp_type;
> +	bp->attr.bp_len  = attr->bp_len;
> +
> +	err = validate_hw_breakpoint(bp);
> +	if (!err && modify)
> +		err = modify_bp_slot(bp, old_type);
> +
> +	if (err) {
> +		bp->attr.bp_addr = old_addr;
> +		bp->attr.bp_type = old_type;
> +		bp->attr.bp_len  = old_len;
> +		return err;
> +	}
> +
> +	bp->attr.disabled = attr->disabled;
> +	return 0;
> +}

I think this function is failing to check if anything else in the attr
changes.

For example, someone could have added PERF_SAMPLE_BRANCH_STACK. That's
something you'll fail to create breakpoints with, but this modification
would 'accept'.