On Wed, Dec 02, 2015 at 12:51:32PM +0000, Wang Nan wrote:
> Before this patch we can trigger a segfault by following steps:
>
> Step 1: perf report
>
> Step 2: Use UP/DOWN to select an entry, don't press 'ENTER'
>
> Step 3: Use '/' to filter symbols, use a filter which returns
> empty result
>
> Step 4: Press 'ENTER' (notice here that the old selection is still
> there. This is another problem)
I guess your data file doesn't contain callchains. Otherwise 'ENTER'
key will toggle it and not show context menu. We now support 'm' key
to show context menu in any case.
>
> Step 5: Press 'ENTER' to annotate that symbol
>
> Step 6: Press 'LEFT' to go out.
>
> Result: segfault:
>
> perf: Segmentation fault
> -------- backtrace --------
> /home/wangnan/perf[0x53e568]
> /lib64/libc.so.6(+0x3545f)[0x7fba75d3245f]
> /home/wangnan/perf[0x537516]
> /home/wangnan/perf[0x533fef]
> /home/wangnan/perf[0x53b347]
> /home/wangnan/perf(perf_evlist__tui_browse_hists+0x96)[0x53d206]
> /home/wangnan/perf(cmd_report+0x1b9f)[0x442c7f]
> /home/wangnan/perf[0x47efa2]
> /home/wangnan/perf(main+0x5f5)[0x432fa5]
> /lib64/libc.so.6(__libc_start_main+0xf4)[0x7fba75d1ebd4]
> /home/wangnan/perf[0x4330d4]
>
> This is because in this case 'nd' could be NULL in
> ui_browser__hists_seek(), but that function never check it.
>
> This patch adds checker for potential NULL pointer in that function.
> After this patch the above steps won't segfault again.
>
> Signed-off-by: Wang Nan <wangn...@huawei.com>
> Cc: Arnaldo Carvalho de Melo <a...@redhat.com>
> Cc: Namhyung Kim <namhy...@kernel.org>
> ---
> tools/perf/ui/browsers/hists.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
> index 33da341..9458da8 100644
> --- a/tools/perf/ui/browsers/hists.c
> +++ b/tools/perf/ui/browsers/hists.c
> @@ -1280,8 +1280,10 @@ static void ui_browser__hists_seek(struct ui_browser
> *browser,
> * Moves not relative to the first visible entry invalidates its
> * row_offset:
> */
> - h = rb_entry(browser->top, struct hist_entry, rb_node);
> - h->row_offset = 0;
> + if (browser->top) {
> + h = rb_entry(browser->top, struct hist_entry, rb_node);
> + h->row_offset = 0;
> + }
Did you have a problem with this code? It seems that
ui_browser__hists_init_top() ensures browser->top is initialized.
>
> /*
> * Here we have to check if nd is expanded (+), if it is we can't go
> @@ -1297,6 +1299,8 @@ static void ui_browser__hists_seek(struct ui_browser
> *browser,
> * and stop when we printed enough lines to fill the screen.
> */
> do_offset:
> + if (!nd)
> + return;
So I guess checking 'nd' being NULL here is enough. And please add a
blank line for readability.
Thanks,
Namhyung
> if (offset > 0) {
> do {
> h = rb_entry(nd, struct hist_entry, rb_node);
> --
> 1.8.3.4
>
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