[PATCH 3/8] perf machine: Guard against NULL strlist in machines__findnew()

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

From: Arnaldo Carvalho de Melo <acme@redhat.com>

The static 'seen' strlist caches guestmount paths that have already
been reported as inaccessible, to avoid repeating the error message.
If strlist__new() fails (OOM), 'seen' stays NULL and the next call
dereferences it via strlist__has_entry() and strlist__add().

Guard both calls so that on allocation failure the error message is
still printed (just not deduplicated) instead of crashing.

Fixes: c80c3c269011 ("perf kvm: Limit repetitive guestmount message to once per directory")
Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/machine.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 8b213482e5648e97..baf855e596c267cd 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -340,9 +340,10 @@ struct machine *machines__findnew(struct machines *machines, pid_t pid)
 			if (!seen)
 				seen = strlist__new(NULL, NULL);
 
-			if (!strlist__has_entry(seen, path)) {
+			if (!seen || !strlist__has_entry(seen, path)) {
 				pr_err("Can't access file %s\n", path);
-				strlist__add(seen, path);
+				if (seen)
+					strlist__add(seen, path);
 			}
 			machine = NULL;
 			goto out;
-- 
2.55.0