From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnaldo Carvalho de Melo Subject: [PATCH 03/19] perf report powerpc: Fix crash if callchain is empty Date: Mon, 25 Jun 2018 14:40:29 -0300 Message-ID: <20180625174045.25765-4-acme@kernel.org> References: <20180625174045.25765-1-acme@kernel.org> Return-path: In-Reply-To: <20180625174045.25765-1-acme@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: Ingo Molnar Cc: Clark Williams , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Sandipan Das , Jiri Olsa , "Naveen N . Rao" , Sukadev Bhattiprolu , Arnaldo Carvalho de Melo List-Id: linux-perf-users.vger.kernel.org From: Sandipan Das For some cases, the callchain provided by the kernel may be empty. So, the callchain ip filtering code will cause a crash if we do not check whether the struct ip_callchain pointer is NULL before accessing any members. This can be observed on a powerpc64le system running Fedora 27 as shown below. # perf record -b -e cycles:u ls Before: # perf report --branch-history perf: Segmentation fault -------- backtrace -------- perf[0x1027615c] linux-vdso64.so.1(__kernel_sigtramp_rt64+0x0)[0x7fff856304d8] perf(arch_skip_callchain_idx+0x44)[0x10257c58] perf[0x1017f2e4] perf(thread__resolve_callchain+0x124)[0x1017ff5c] perf(sample__resolve_callchain+0xf0)[0x10172788] ... After: # perf report --branch-history Samples: 25 of event 'cycles:u', Event count (approx.): 2306870 Overhead Source:Line Symbol Shared Object + 11.60% _init+35736 [.] _init ls + 9.84% strcoll_l.c:137 [.] __strcoll_l libc-2.26.so + 9.16% memcpy.S:175 [.] __memcpy_power7 libc-2.26.so + 9.01% gconv_charset.h:54 [.] _nl_find_locale libc-2.26.so + 8.87% dl-addr.c:52 [.] _dl_addr libc-2.26.so + 8.83% _init+236 [.] _init ls ... Reported-by: Ravi Bangoria Signed-off-by: Sandipan Das Acked-by: Ravi Bangoria Cc: Jiri Olsa Cc: Naveen N. Rao Cc: Sukadev Bhattiprolu Link: http://lkml.kernel.org/r/20180611104049.11048-1-sandipan@linux.ibm.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/arch/powerpc/util/skip-callchain-idx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/perf/arch/powerpc/util/skip-callchain-idx.c b/tools/perf/arch/powerpc/util/skip-callchain-idx.c index 3598b8b75d27..ef5d59a5742e 100644 --- a/tools/perf/arch/powerpc/util/skip-callchain-idx.c +++ b/tools/perf/arch/powerpc/util/skip-callchain-idx.c @@ -243,7 +243,7 @@ int arch_skip_callchain_idx(struct thread *thread, struct ip_callchain *chain) u64 ip; u64 skip_slot = -1; - if (chain->nr < 3) + if (!chain || chain->nr < 3) return skip_slot; ip = chain->ips[2]; -- 2.14.3