From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 736D5283FEB; Tue, 1 Jul 2025 20:10:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751400629; cv=none; b=m/Bn8TSW2OnSSIEZoXiX1HAwuFJzFLwZ/E+BBSxhcK+NMwnQzcPQ+lN/QVd05EFnZg61FxHpWjdxTNNOtQzm/Z2QggkJ+pVj5k79YO1v048bw4fsrE21/RLy9QV4EdptNvDXZrudIrIoBLgQDYUgB9OrqETf54EWYpqImXYOku4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751400629; c=relaxed/simple; bh=x/5s4J6/OTlD9f6oui9G3mjn+w+/x+w57+m2VNsLM1E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tnlKdCynkg6hUGuLuuPecDhWhNup7K8DSwUkiL4xHVniH48JAb2M38zQCiRbIFaBvLkdJyV1sLSQNuUuknWJFQjZTg/LQqSL9Bt8NKtQkZ0flVcksWUXnsdmKNMUm0Ne46w78LvtRiq4iNuYAYzfMaHP4lN/9tgL5++ADtr0ILs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=U+BCvdeo; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="U+BCvdeo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AC641C4CEF3; Tue, 1 Jul 2025 20:10:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1751400629; bh=x/5s4J6/OTlD9f6oui9G3mjn+w+/x+w57+m2VNsLM1E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=U+BCvdeo1cmca9l8ZVxpggYM47Mzux1ylSpxvUFJU3ciYBv46iqTHt+NSw5TtqgGP tEFBVMkOWtehGGYY3vPc1WXMOICGzg7d9K6INX1GdMIqyzT1+Hmqdhb0E/XelzsKtW /WXJvpwRgddPVBDu/fkI3bSdfpvNjHdIJ3expw+Kshy/JSclR1+aao97Td02nFDUmW N2yeH/NNOO9RgH30lexA7UXkuIGVUsa7EVdZrmDPis3KpFATwTxpSjY9phHpje1dzo WnevEb2BLwf5viqV5RQ9QvB5nu7Tp5Quh5jZEwzkxUR6pK/neKR55VJMTjOIAEsE5G bPOZ7NksshPYQ== From: Namhyung Kim To: Arnaldo Carvalho de Melo , Ian Rogers , Kan Liang Cc: Jiri Olsa , Adrian Hunter , Peter Zijlstra , Ingo Molnar , LKML , linux-perf-users@vger.kernel.org Subject: [PATCH v2 3/3] perf tools: Fix use-after-free in help_unknown_cmd() Date: Tue, 1 Jul 2025 13:10:27 -0700 Message-ID: <20250701201027.1171561-3-namhyung@kernel.org> X-Mailer: git-send-email 2.50.0.727.gbf7dc18ff4-goog In-Reply-To: <20250701201027.1171561-1-namhyung@kernel.org> References: <20250701201027.1171561-1-namhyung@kernel.org> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Currently perf aborts when it finds an invalid command. I guess it depends on the environment as I have some custom commands in the path. $ perf bad-command perf: 'bad-command' is not a perf-command. See 'perf --help'. Aborted (core dumped) It's because the exclude_cmds() in libsubcmd has a use-after-free when it removes some entries. After copying one to another entry, it keeps the pointer in the both position. And the next copy operation will free the later one but it's the same entry in the previous one. For example, let's say cmds = { A, B, C, D, E } and excludes = { B, E }. ci cj ei cmds-name excludes -----------+-------------------- 0 0 0 | A B : cmp < 0, ci == cj 1 1 0 | B B : cmp == 0 2 1 1 | C E : cmp < 0, ci != cj At this point, it frees cmds->names[1] and cmds->names[1] is assigned to cmds->names[2]. 3 2 1 | D E : cmp < 0, ci != cj Now it frees cmds->names[2] but it's the same as cmds->names[1]. So accessing cmds->names[1] will be invalid. This makes the subcmd tests succeed. $ perf test subcmd 69: libsubcmd help tests : 69.1: Load subcmd names : Ok 69.2: Uniquify subcmd names : Ok 69.3: Exclude duplicate subcmd names : Ok Fixes: 657a3efee43a ("libsubcmd: Avoid SEGV/use-after-free when commands aren't excluded") Reviewed-by: Ian Rogers Signed-off-by: Namhyung Kim --- tools/lib/subcmd/help.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/tools/lib/subcmd/help.c b/tools/lib/subcmd/help.c index 8561b0f01a247690..9ef569492560efd7 100644 --- a/tools/lib/subcmd/help.c +++ b/tools/lib/subcmd/help.c @@ -9,6 +9,7 @@ #include #include #include +#include #include "subcmd-util.h" #include "help.h" #include "exec-cmd.h" @@ -82,10 +83,11 @@ void exclude_cmds(struct cmdnames *cmds, struct cmdnames *excludes) ci++; cj++; } else { - zfree(&cmds->names[cj]); - cmds->names[cj++] = cmds->names[ci++]; + cmds->names[cj++] = cmds->names[ci]; + cmds->names[ci++] = NULL; } } else if (cmp == 0) { + zfree(&cmds->names[ci]); ci++; ei++; } else if (cmp > 0) { @@ -94,12 +96,12 @@ void exclude_cmds(struct cmdnames *cmds, struct cmdnames *excludes) } if (ci != cj) { while (ci < cmds->cnt) { - zfree(&cmds->names[cj]); - cmds->names[cj++] = cmds->names[ci++]; + cmds->names[cj++] = cmds->names[ci]; + cmds->names[ci++] = NULL; } } for (ci = cj; ci < cmds->cnt; ci++) - zfree(&cmds->names[ci]); + assert(cmds->names[ci] == NULL); cmds->cnt = cj; } -- 2.50.0.727.gbf7dc18ff4-goog