Messages in this thread Patch in this message | | | Date | Tue, 11 Apr 2017 09:35:45 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCH v2] perf: fix double free at function perf_hpp__reset_output_field |
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On Tue, Apr 11, 2017 at 11:06:14AM +0800, Du, Changbin wrote:
SNIP
> > the original code takes it out of both lists, > > so the next itaration won't go over that entry > > > oh, my bad, my desc is wrong. I replayed the crash. The problem is > list_del_init a unlinked entry. > > perf: Segmentation fault > -------- backtrace -------- > ./perf[0x57394b] > /lib/x86_64-linux-gnu/libc.so.6(+0x354b0)[0x7fb8da3034b0] > ./perf(perf_hpp__reset_output_field+0xb7)[0x55dfe7] > ./perf(hists__sort_by_fields+0x3d7)[0x509777] > ./perf[0x5704c1] > ./perf(perf_evlist__tui_browse_hists+0x2e5)[0x5723e5] > ./perf(cmd_report+0x1a9b)[0x43b4fb] > ./perf[0x494731] > ./perf(main+0x704)[0x426304] > /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0)[0x7fb8da2ee830] > ./perf(_start+0x29)[0x4263f9] > [0x0] > > (gdb) print fmt.list > $4 = {next = 0x100, prev = 0x200} // LIST_POISON > (gdb) print fmt.sort_list > $5 = {next = 0x9727d0 <perf_hpp_list+16>, prev = 0x9727d0 <perf_hpp_list+16>} > > In this case, the fmt is linked in sort_list, but not in list. So crash > at the list_del_init(&fmt->list) of second loop.
so the only place I can see the POISON could get there is in perf_hpp__column_unregister.. can't we just get rid of it like below
jirka
--- diff --git a/tools/perf/ui/hist.c b/tools/perf/ui/hist.c index 5d632dca672a..7577effbf746 100644 --- a/tools/perf/ui/hist.c +++ b/tools/perf/ui/hist.c @@ -529,7 +529,7 @@ void perf_hpp_list__prepend_sort_field(struct perf_hpp_list *list, void perf_hpp__column_unregister(struct perf_hpp_fmt *format) { - list_del(&format->list); + list_del_init(&format->list); } void perf_hpp__cancel_cumulate(void)
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