Messages in this thread Patch in this message | | | Date | Mon, 27 Apr 2015 13:20:22 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [RESEND PATCH] perf: top: fix a segfault when kernel map is restricted. |
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Em Sat, Apr 25, 2015 at 07:25:03AM +0000, Wang Nan escreveu: > 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]
Thanks for the detailed report, I reproduced the problem here and I am applying the patch.
- Arnaldo > 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@entry=0x7fffffffa8a0, idx=idx@entry=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@entry=0x8a6ce8 <commands+264>, argc=argc@entry=3, argv=argv@entry=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@huawei.com> > --- > > I don't receive previous mail from the list so send it again. > > --- > > 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); > -- > 1.8.3.4
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