FAILED: patch "[PATCH] perf evsel: Close the fds opened so far when disabling missing features" failed to apply to 6.18-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 16d1234793d42a5a594db99522845996ab8e0d29
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107051229-failed-6.18-16d1234793d4@kernel.org' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From 16d1234793d42a5a594db99522845996ab8e0d29 Mon Sep 17 00:00:00 2001
From: Arnaldo Carvalho de Melo <acme@redhat.com>
Date: Thu, 15 Oct 2026 22:07:03 -0300
Subject: [PATCH] perf evsel: Close the fds opened so far when disabling
 missing features

evsel__open_cpu() opens the events one by one and, when an open fails
with EINVAL and evsel__detect_missing_features() has a feature to leave
out, goes back to fallback_missing_features to open them all again from
start_cpu_map_idx, without closing what the abandoned attempt opened:
the fd of every CPU or thread that was opened before the failing one is
overwritten in the FD() array, leaking it.

Close them first, the same way out_close does when returning an error,
leaving the entries at -1 for the retry.

Fixes: af954f76eea5 ("perf tools: Check fallback error and order")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/r/sashiko-outbox-173532@kernel.org
Reviewed-by: Ian Rogers <irogers@google.com>
Tested-by: Ian Rogers <irogers@google.com>
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/evsel.c | 30 +++++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 59318fef03cb1..d060fca8090f6 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -3005,6 +3005,19 @@ static bool evsel__detect_missing_features(struct evsel *evsel, struct perf_cpu
 	return false;
 }
 
+static void evsel__close_fds(struct evsel *evsel, int start_cpu_map_idx,
+			     int cpu_map_idx, int thread, int nthreads)
+{
+	do {
+		while (--thread >= 0) {
+			if (FD(evsel, cpu_map_idx, thread) >= 0)
+				close(FD(evsel, cpu_map_idx, thread));
+			FD(evsel, cpu_map_idx, thread) = -1;
+		}
+		thread = nthreads;
+	} while (--cpu_map_idx >= start_cpu_map_idx);
+}
+
 static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 		struct perf_thread_map *threads,
 		int start_cpu_map_idx, int end_cpu_map_idx)
@@ -3150,8 +3163,14 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 	if (err == -EMFILE && rlimit__increase_nofile(&set_rlimit))
 		goto retry_open;
 
-	if (err == -EINVAL && evsel__detect_missing_features(evsel, cpu))
+	if (err == -EINVAL && evsel__detect_missing_features(evsel, cpu)) {
+		/*
+		 * The restart opens the events again, so close what this
+		 * attempt opened before its entries are overwritten.
+		 */
+		evsel__close_fds(evsel, start_cpu_map_idx, idx, thread, nthreads);
 		goto fallback_missing_features;
+	}
 
 	if (evsel__precise_ip_fallback(evsel))
 		goto retry_open;
@@ -3161,14 +3180,7 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 		threads->err_thread = thread;
 
 	old_errno = errno;
-	do {
-		while (--thread >= 0) {
-			if (FD(evsel, idx, thread) >= 0)
-				close(FD(evsel, idx, thread));
-			FD(evsel, idx, thread) = -1;
-		}
-		thread = nthreads;
-	} while (--idx >= start_cpu_map_idx);
+	evsel__close_fds(evsel, start_cpu_map_idx, idx, thread, nthreads);
 	errno = old_errno;
 out:
 	if (err)
-- 
2.53.0