4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Sandipan Das <sandipan@xxxxxxxxxxxxx>
[ Upstream commit 143c99f6ac6812d23254e80844d6e34be897d3e1 ]
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 <ravi.bangoria@xxxxxxxxxxxxx>
Signed-off-by: Sandipan Das <sandipan@xxxxxxxxxxxxx>
Acked-by: Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
Cc: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20180611104049.11048-1-sandipan@xxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
tools/perf/arch/powerpc/util/skip-callchain-idx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- 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 threa
u64 ip;
u64 skip_slot = -1;
- if (chain->nr < 3)
+ if (!chain || chain->nr < 3)
return skip_slot;
ip = chain->ips[2];
