[PATCH] perf pmus: Fixes always false when compare duplicates aliases

[PATCH] perf pmus: Fixes always false when compare duplicates aliases

[Junhao He]

In the previous loop, all the members in the aliases[j-1] have been freed
and set to NULL. But in this loop, the function pmu_alias_is_duplicate()
compares the aliases[j] with the aliases[j-1] that has already been
disposed, so the function will always return false and duplicate aliases
will never be discarded.

If we find duplicate aliases, it skips the zfree aliases[j], which is
accompanied by a memory leak.

We can use the next aliases[j+1] to theck for duplicate aliases to
fixes the aliases NULL pointer dereference, then goto zfree code snippet
to release it.

After patch testing:
 $ perf list --unit=hisi_sicl,cpa pmu

 uncore cpa:
   cpa_p0_rd_dat_32b
        [Number of read ops transmitted by the P0 port which size is 32 bytes.
         Unit: hisi_sicl,cpa]
   cpa_p0_rd_dat_64b
        [Number of read ops transmitted by the P0 port which size is 64 bytes.
         Unit: hisi_sicl,cpa]

Fixes: c3245d2093c1 ("perf pmu: Abstract alias/event struct")
Signed-off-by: Junhao He <hejunhao3@huawei.com>
---
 tools/perf/util/pmus.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c
index b9b4c5eb5002..6907e3e7fbd1 100644
--- a/tools/perf/util/pmus.c
+++ b/tools/perf/util/pmus.c
@@ -477,8 +477,8 @@ void perf_pmus__print_pmu_events(const struct print_callbacks *print_cb, void *p
 	qsort(aliases, len, sizeof(struct sevent), cmp_sevent);
 	for (int j = 0; j < len; j++) {
 		/* Skip duplicates */
-		if (j > 0 && pmu_alias_is_duplicate(&aliases[j], &aliases[j - 1]))
-			continue;
+		if (j < len - 1 && pmu_alias_is_duplicate(&aliases[j], &aliases[j + 1]))
+			goto free;
 
 		print_cb->print_event(print_state,
 				aliases[j].pmu_name,
@@ -491,6 +491,7 @@ void perf_pmus__print_pmu_events(const struct print_callbacks *print_cb, void *p
 				aliases[j].desc,
 				aliases[j].long_desc,
 				aliases[j].encoding_desc);
+free:
 		zfree(&aliases[j].name);
 		zfree(&aliases[j].alias);
 		zfree(&aliases[j].scale_unit);
-- 
2.33.0

Re: [PATCH] perf pmus: Fixes always false when compare duplicates aliases

[Namhyung Kim]

On Fri, 14 Jun 2024 17:43:18 +0800, Junhao He wrote:

> In the previous loop, all the members in the aliases[j-1] have been freed
> and set to NULL. But in this loop, the function pmu_alias_is_duplicate()
> compares the aliases[j] with the aliases[j-1] that has already been
> disposed, so the function will always return false and duplicate aliases
> will never be discarded.
> 
> If we find duplicate aliases, it skips the zfree aliases[j], which is
> accompanied by a memory leak.
> 
> [...]

Applied to perf-tools-next, thanks!

Best regards,
Namhyung