linux-kernel - [PATCH v1] lib subcmd: Avoid use-after-free when no commands are excluded

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Message-Id: <20230626222213.366550-1-irogers@google.com>
Date:   Mon, 26 Jun 2023 15:22:13 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Ian Rogers <irogers@...gle.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Chenyuan Mi <cymi20@...an.edu.cn>, linux-kernel@...r.kernel.org
Subject: [PATCH v1] lib subcmd: Avoid use-after-free when no commands are excluded

The array shortening may be an unnecessary array copy. Before commit
657a3efee43a ("lib subcmd: Avoid memory leak in exclude_cmds") this
was benign, but afterwards this could lead to a segv.

Fixes: 657a3efee43a ("lib subcmd: Avoid memory leak in exclude_cmds")
Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/lib/subcmd/help.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/tools/lib/subcmd/help.c b/tools/lib/subcmd/help.c
index 67a8d6b740ea..b59ca17e406d 100644
--- a/tools/lib/subcmd/help.c
+++ b/tools/lib/subcmd/help.c
@@ -77,10 +77,11 @@ void exclude_cmds(struct cmdnames *cmds, struct cmdnames *excludes)
 			ei++;
 		}
 	}
-
-	while (ci < cmds->cnt) {
-		zfree(&cmds->names[cj]);
-		cmds->names[cj++] = cmds->names[ci++];
+	if (ci != cj) {
+		while (ci < cmds->cnt) {
+			zfree(&cmds->names[cj]);
+			cmds->names[cj++] = cmds->names[ci++];
+		}
 	}
 	for (ci = cj; ci < cmds->cnt; ci++)
 		zfree(&cmds->names[ci]);
-- 
2.41.0.162.gfafddb0af9-goog