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

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Date: Fri, 14 Jun 2024 17:43:18 +0800
From: Junhao He <hejunhao3@...wei.com>
To: <peterz@...radead.org>, <acme@...hat.com>, <irogers@...gle.com>
CC: <jonathan.cameron@...wei.com>, <yangyicong@...wei.com>,
	<linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linuxarm@...wei.com>, <prime.zeng@...ilicon.com>, <hejunhao3@...wei.com>,
	<adrian.hunter@...el.com>, <alexander.shishkin@...ux.intel.com>,
	<cuigaosheng1@...wei.com>, <mingo@...hat.com>, <james.clark@....com>,
	<renyu.zj@...ux.alibaba.com>, <jolsa@...nel.org>, <john.g.garry@...cle.com>,
	<kjain@...ux.ibm.com>, <kan.liang@...ux.intel.com>, <mark.rutland@....com>,
	<namhyung@...nel.org>, <ravi.bangoria@....com>, <robh@...nel.org>,
	<linux-perf-users@...r.kernel.org>
Subject: [PATCH] perf pmus: Fixes always false when compare duplicates aliases

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@...wei.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