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Message-ID: <tip-c671835021798c1c40ca0b55b49feff76ed5e0e1@git.kernel.org>
Date: Fri, 1 May 2015 03:14:56 -0700
From: tip-bot for Wang Nan <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: lizefan@...wei.com, hpa@...or.com, jolsa@...nel.org,
paulus@...ba.org, a.p.zijlstra@...llo.nl, wangnan0@...wei.com,
tglx@...utronix.de, acme@...hat.com, mingo@...nel.org,
linux-kernel@...r.kernel.org, dsahern@...il.com
Subject: [tip:perf/urgent] perf top:
Fix a segfault when kernel map is restricted.
Commit-ID: c671835021798c1c40ca0b55b49feff76ed5e0e1
Gitweb: http://git.kernel.org/tip/c671835021798c1c40ca0b55b49feff76ed5e0e1
Author: Wang Nan <wangnan0@...wei.com>
AuthorDate: Sat, 25 Apr 2015 07:25:03 +0000
Committer: Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Mon, 27 Apr 2015 13:24:32 -0300
perf top: Fix a segfault when kernel map is restricted.
Perf top raise a warning if a kernel sample is collected but kernel map
is restricted. The warning message needs to dereference al.map->dso...
However, previous perf_event__preprocess_sample() doesn't always
guarantee al.map != NULL, for example, when kernel map is restricted.
This patch validates al.map before dereferencing, avoid the segfault.
Before this patch:
$ cat /proc/sys/kernel/kptr_restrict
1
$ perf top -p 120183
perf: Segmentation fault
-------- backtrace --------
/path/to/perf[0x509868]
/lib64/libc.so.6(+0x3545f)[0x7f9a1540045f]
/path/to/perf[0x448820]
/path/to/perf(cmd_top+0xe3c)[0x44a5dc]
/path/to/perf[0x4766a2]
/path/to/perf(main+0x5f5)[0x42e545]
/lib64/libc.so.6(__libc_start_main+0xf4)[0x7f9a153ecbd4]
/path/to/perf[0x42e674]
And gdb call trace:
Program received signal SIGSEGV, Segmentation fault.
perf_event__process_sample (machine=0xa44030, sample=0x7fffffffa4c0, evsel=0xa43b00, event=0x7ffff41c3000, tool=0x7fffffffa8a0)
at builtin-top.c:736
736 !RB_EMPTY_ROOT(&al.map->dso->symbols[MAP__FUNCTION]) ?
(gdb) bt
#0 perf_event__process_sample (machine=0xa44030, sample=0x7fffffffa4c0, evsel=0xa43b00, event=0x7ffff41c3000, tool=0x7fffffffa8a0)
at builtin-top.c:736
#1 perf_top__mmap_read_idx (top=top@...ry=0x7fffffffa8a0, idx=idx@...ry=0) at builtin-top.c:855
#2 0x000000000044a5dd in perf_top__mmap_read (top=0x7fffffffa8a0) at builtin-top.c:872
#3 __cmd_top (top=0x7fffffffa8a0) at builtin-top.c:997
#4 cmd_top (argc=<optimized out>, argv=<optimized out>, prefix=<optimized out>) at builtin-top.c:1267
#5 0x00000000004766a3 in run_builtin (p=p@...ry=0x8a6ce8 <commands+264>, argc=argc@...ry=3, argv=argv@...ry=0x7fffffffdf70)
at perf.c:371
#6 0x000000000042e546 in handle_internal_command (argv=0x7fffffffdf70, argc=3) at perf.c:430
#7 run_argv (argv=0x7fffffffdcf0, argcp=0x7fffffffdcfc) at perf.c:474
#8 main (argc=3, argv=0x7fffffffdf70) at perf.c:589
(gdb)
Signed-off-by: Wang Nan <wangnan0@...wei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Zefan Li <lizefan@...wei.com>
Link: http://lkml.kernel.org/r/1429946703-80807-1-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
tools/perf/builtin-top.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 1cb3436..6a4d5d4 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -733,7 +733,7 @@ static void perf_event__process_sample(struct perf_tool *tool,
"Kernel address maps (/proc/{kallsyms,modules}) are restricted.\n\n"
"Check /proc/sys/kernel/kptr_restrict.\n\n"
"Kernel%s samples will not be resolved.\n",
- !RB_EMPTY_ROOT(&al.map->dso->symbols[MAP__FUNCTION]) ?
+ al.map && !RB_EMPTY_ROOT(&al.map->dso->symbols[MAP__FUNCTION]) ?
" modules" : "");
if (use_browser <= 0)
sleep(5);
--
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