Messages in this thread Patch in this message | | | From | Wang Nan <> | Subject | [PATCH 1/2] perf hists browser: Add NULL pointer check to prevent crash | Date | Wed, 2 Dec 2015 12:51:32 +0000 |
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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)
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 <wangnan0@huawei.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Namhyung Kim <namhyung@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; + } /* * 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; if (offset > 0) { do { h = rb_entry(nd, struct hist_entry, rb_node); -- 1.8.3.4
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