Re: [PATCH] perf hist: Update hist symbol when updating maps

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Thu, Aug 15, 2024 at 03:22:12PM +0100, Matt Fleming wrote:
> AddressSanitizer found a use-after-free bug in the symbol code which
> manifested as perf top segfaulting.
> 
>   ==1238389==ERROR: AddressSanitizer: heap-use-after-free on address 0x60b00c48844b at pc 0x5650d8035961 bp 0x7f751aaecc90 sp 0x7f751aaecc80
>   READ of size 1 at 0x60b00c48844b thread T193
>       #0 0x5650d8035960 in _sort__sym_cmp util/sort.c:310
>       #1 0x5650d8043744 in hist_entry__cmp util/hist.c:1286
>       #2 0x5650d8043951 in hists__findnew_entry util/hist.c:614
>       #3 0x5650d804568f in __hists__add_entry util/hist.c:754
>       #4 0x5650d8045bf9 in hists__add_entry util/hist.c:772
>       #5 0x5650d8045df1 in iter_add_single_normal_entry util/hist.c:997
>       #6 0x5650d8043326 in hist_entry_iter__add util/hist.c:1242
>       #7 0x5650d7ceeefe in perf_event__process_sample /home/matt/src/linux/tools/perf/builtin-top.c:845
>       #8 0x5650d7ceeefe in deliver_event /home/matt/src/linux/tools/perf/builtin-top.c:1208
>       #9 0x5650d7fdb51b in do_flush util/ordered-events.c:245
>       #10 0x5650d7fdb51b in __ordered_events__flush util/ordered-events.c:324
>       #11 0x5650d7ced743 in process_thread /home/matt/src/linux/tools/perf/builtin-top.c:1120
>       #12 0x7f757ef1f133 in start_thread nptl/pthread_create.c:442
>       #13 0x7f757ef9f7db in clone3 ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
> 
> When updating hist maps it's also necessary to update the hist symbol
> reference because the old one gets freed in map__put().
> 
> While this bug was probably introduced with 5c24b67aae72 ("perf tools:
> Replace map->referenced & maps->removed_maps with map->refcnt"), the
> symbol objects were leaked until c087e9480cf3 ("perf machine: Fix
> refcount usage when processing PERF_RECORD_KSYMBOL") was merged so the
> bug was masked.

Great analysis, thanks a lot, applied.

- Arnaldo
 
> Fixes: c087e9480cf3 ("perf machine: Fix refcount usage when processing PERF_RECORD_KSYMBOL")
> Signed-off-by: Matt Fleming (Cloudflare) <matt@readmodwrite.com>
> Reported-by: Yunzhao Li <yunzhao@cloudflare.com>
> Cc: stable@vger.kernel.org # v5.13+
> ---
>  tools/perf/util/hist.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
> index 0f554febf9a1..0f9ce2ee2c31 100644
> --- a/tools/perf/util/hist.c
> +++ b/tools/perf/util/hist.c
> @@ -639,6 +639,11 @@ static struct hist_entry *hists__findnew_entry(struct hists *hists,
>  			 * the history counter to increment.
>  			 */
>  			if (he->ms.map != entry->ms.map) {
> +				if (he->ms.sym) {
> +					u64 addr = he->ms.sym->start;
> +					he->ms.sym = map__find_symbol(entry->ms.map, addr);
> +				}
> +
>  				map__put(he->ms.map);
>  				he->ms.map = map__get(entry->ms.map);
>  			}
> -- 
> 2.34.1
>