Messages in this thread | | | Subject | Re: [PATCH 5/5] perf tools: Fix NULL pointer deference when vdso not found | From | Hekuang <> | Date | Thu, 23 Jun 2016 11:03:11 +0800 |
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在 2016/6/23 10:02, Wangnan (F) 写道: > Hi, > > This patch fixes a real crash problem when we do 'perf report' > on an arm64 platform with arm32 program. > It is introduced by commit f9b2bdf228 ("perf tools: Find vdso > with the consider of cross-platform"). From dmesg report, perf > crashes in dso__type() because dso is NULL. > > Still don't know why on x86 it never crash, but it is obviously
This is because the fault only occured while dso_type==DSO__TYPE_32BIT, run 64bit executable won't enter the fault branch, but if we run a 32bit executable on x86_64, this bug can be reproduced easily.
# file ~/hello ~/hello: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 4.5.0, not stripped
# perf record -g hello Segmentation fault
Thank you.
> that we need to check the return vaule from __dso__find(): it can > be NULL. > > So please consider pulling. > > Thank you. > > On 2016/6/22 14:57, He Kuang wrote: >> We should check if 'dso' is a null pointer before passing it to the >> function dso__type(), otherwise a segfault will be raised in >> dso__data_get_fd(). In function machine__find_vdso(), the return value >> checking of 'dso' is missed and this patch fixes this issue. >> >> Signed-off-by: He Kuang <hekuang@huawei.com> >> --- >> tools/perf/util/vdso.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/tools/perf/util/vdso.c b/tools/perf/util/vdso.c >> index 8f81c41..7bdcad4 100644 >> --- a/tools/perf/util/vdso.c >> +++ b/tools/perf/util/vdso.c >> @@ -296,7 +296,7 @@ static struct dso *machine__find_vdso(struct >> machine *machine, >> if (!dso) { >> dso = __dsos__find(&machine->dsos, DSO__NAME_VDSO, >> true); >> - if (dso_type != dso__type(dso, machine)) >> + if (dso && dso_type != dso__type(dso, machine)) >> dso = NULL; >> } >> break; > > >
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