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Date: Mon, 27 Nov 2017 15:07:47 -0800
From: Andi Kleen <ak@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Milind Chabbi <chabbi.milind@gmail.com>, Jiri Olsa <jolsa@redhat.com>,
        Jiri Olsa <jolsa@kernel.org>, Ingo Molnar <mingo@kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        lkml <linux-kernel@vger.kernel.org>,
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        Hari Bathini <hbathini@linux.vnet.ibm.com>,
        Jin Yao <yao.jin@linux.intel.com>, Kan Liang <kan.liang@intel.com>,
        Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>,
        Oleg Nesterov <onestero@redhat.com>, Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH 4/6] hw_breakpoint: Factor out
 __modify_user_hw_breakpoint function
Message-ID: <20171127230747.GC3070@tassilo.jf.intel.com>
References: <20171127162133.21163-1-jolsa@kernel.org>
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On Mon, Nov 27, 2017 at 11:01:28PM +0100, Peter Zijlstra wrote:
> On Mon, Nov 27, 2017 at 01:50:30PM -0800, Milind Chabbi wrote:
> > The possible checks is infinite
> 
> struct perf_event_attr is very much a finite data type.
> 
> Something as simple as:
> 
> 	struct perf_event_attr tmp1 = new_attr, tmp2 = event->attr;
> 
> 	tmp1.bp_type = tmp2.bp_type;
> 	tmp1.bp_addr = tmp2.bp_addr;
> 	tmp1.bp_len  = tmp2.bp_len;
> 
> 	if (memcmp(&tmp1, &tmp2, sizeof(tmp1)))
> 		return -EINVAL;
> 
> would actually do the checks __modify_user_hw_breakpoint() needs to do.

It could fail with uninitialized padding.


-Andi