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Tue, 11 Aug 2026 15:31:30 +0000 Message-ID: Date: Tue, 11 Aug 2026 18:31:22 +0300 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/9] perf thread-stack: Bound wrapped branch stack copy To: Amir Ayupov , , , , "Suzuki K Poulose" , James Clark , "Leo Yan" , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , "Alexander Shishkin" , Jiri Olsa , Ian Rogers , John Garry , "Will Deacon" CC: , Mike Leach , "Jonathan Corbet" , Shuah Khan , "Swapnil Sapkal" References: <20260803090640.2412336-1-aaupov@fb.com> <20260803090640.2412336-3-aaupov@fb.com> Content-Language: en-US From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: c/o Alberga Business Park, 6 krs, Bertel Jungin Aukio 5, 02600 Espoo, Business Identity Code: 0357606 - 4, Domiciled in Helsinki In-Reply-To: <20260803090640.2412336-3-aaupov@fb.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: DU2PR04CA0295.eurprd04.prod.outlook.com (2603:10a6:10:28c::30) To IA1PR11MB7198.namprd11.prod.outlook.com (2603:10b6:208:419::15) Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: IA1PR11MB7198:EE_|CO1PR11MB4833:EE_ X-MS-Office365-Filtering-Correlation-Id: 2288d028-3964-4e3d-d108-08def7bd9dd2 X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|7416014|376014|1800799024|366016|921020|6133799003|56012099006|10067099003|11063799006|4143699003|3023799007|18002099003|22082099003; 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> > but then copies ts->br_stack_pos entries regardless, overrunning the > destination whenever sz is smaller than ts->br_stack_pos. > > No caller can trigger this today: both intel-pt and cs-etm size the > thread stack ring and the output buffer from the same > synth_opts.last_branch_sz, so sz is never less than ts->br_stack_sz and > the two values always agree. It becomes reachable as soon as a caller > keeps a larger reconstruction ring than the requested output depth, > which is what --itrace=L does for late branch sampling. > > Copy nr entries instead, so the destination bound is honoured whatever > the caller asks for. > > Signed-off-by: Amir Ayupov > --- > tools/perf/util/thread-stack.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/perf/util/thread-stack.c b/tools/perf/util/thread-stack.c > index 1a3dffa83bde2..51eaedb47bb1d 100644 > --- a/tools/perf/util/thread-stack.c > +++ b/tools/perf/util/thread-stack.c > @@ -643,7 +643,7 @@ void thread_stack__br_sample(struct thread *thread, int cpu, > sz -= nr; > be = &dst->entries[nr]; > nr = min(ts->br_stack_pos, sz); > - memcpy(be, &src->entries[0], bsz * ts->br_stack_pos); > + memcpy(be, &src->entries[0], bsz * nr); > } > } > Has since been done: commit ab9c84d1cd59e6b3b73de34982a35a76e3a9b032 Author: Arnaldo Carvalho de Melo Date: Mon Jul 27 13:17:01 2026 -0300 perf thread-stack: Fix heap buffer overflow on branch stack wrap copy thread_stack__br_sample() copies the wrap-around portion of the branch stack ring buffer with: nr = min(ts->br_stack_pos, sz); memcpy(be, &src->entries[0], bsz * ts->br_stack_pos); 'nr' is correctly bounded to min(br_stack_pos, sz) but the memcpy uses the unbounded ts->br_stack_pos directly. When br_stack_pos exceeds the remaining destination space 'sz', this writes past the destination buffer. Use 'nr' (the bounded value) in the memcpy size, matching the pattern of the first memcpy in the same function. Fixes: 86d67180b920 ("perf thread-stack: Add branch stack support") Reported-by: sashiko-bot Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo Reviewed-by: James Clark Reviewed-by: Adrian Hunter Signed-off-by: Namhyung Kim diff --git a/tools/perf/util/thread-stack.c b/tools/perf/util/thread-stack.c index c5ce741b0744..1360f44421ef 100644 --- a/tools/perf/util/thread-stack.c +++ b/tools/perf/util/thread-stack.c @@ -642,7 +642,7 @@ void thread_stack__br_sample(struct thread *thread, int cpu, sz -= nr; be = &dst->entries[nr]; nr = min(ts->br_stack_pos, sz); - memcpy(be, &src->entries[0], bsz * ts->br_stack_pos); + memcpy(be, &src->entries[0], bsz * nr); } }