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[179.240.145.61]) by smtp.gmail.com with ESMTPSA id u63sm1222212qkh.85.2019.06.17.10.32.06 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 17 Jun 2019 10:32:06 -0700 (PDT) From: Arnaldo Carvalho de Melo X-Google-Original-From: Arnaldo Carvalho de Melo Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 8246541149; Mon, 17 Jun 2019 14:32:03 -0300 (-03) Date: Mon, 17 Jun 2019 14:32:03 -0300 To: Leo Yan Cc: Alexander Shishkin , Jiri Olsa , Namhyung Kim , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH 2/2] perf trace: Handle NULL pointer dereference in trace__syscall_info() Message-ID: <20190617173203.GA23094@kernel.org> References: <20190617091140.24372-1-leo.yan@linaro.org> <20190617091140.24372-2-leo.yan@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190617091140.24372-2-leo.yan@linaro.org> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Mon, Jun 17, 2019 at 05:11:40PM +0800, Leo Yan escreveu: > trace__init_bpf_map_syscall_args() invokes trace__syscall_info() to > retrieve system calls information, it always passes NULL for 'evsel' > argument; when id is an invalid value then the logging will try to > output event name, this triggers NULL pointer dereference. > > This patch directly uses string "unknown" for event name when 'evsel' > is NULL pointer. > > Signed-off-by: Leo Yan > --- > tools/perf/builtin-trace.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c > index 5cd74651db4c..49dfb2fd393b 100644 > --- a/tools/perf/builtin-trace.c > +++ b/tools/perf/builtin-trace.c > @@ -1764,7 +1764,7 @@ static struct syscall *trace__syscall_info(struct trace *trace, > static u64 n; > > pr_debug("Invalid syscall %d id, skipping (%s, %" PRIu64 ")\n", > - id, perf_evsel__name(evsel), ++n); > + id, evsel ? perf_evsel__name(evsel) : "unknown", ++n); > return NULL; What do you think of this instead? diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index 68beef8f47ff..1d6af95b9207 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -590,6 +590,9 @@ const char *perf_evsel__name(struct perf_evsel *evsel) { char bf[128]; + if (!evsel) + goto out_unknown; + if (evsel->name) return evsel->name; @@ -629,7 +632,10 @@ const char *perf_evsel__name(struct perf_evsel *evsel) evsel->name = strdup(bf); - return evsel->name ?: "unknown"; + if (evsel->name) + return evsel->name; +out_unknown: + return "unknown"; } const char *perf_evsel__group_name(struct perf_evsel *evsel)