From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 F02FC376A00; Wed, 10 Jun 2026 19:52:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781121162; cv=none; b=o6+QvWyVxvPBrbVQbB1sZEoDgWH4ATgf/rHk7rx2ts3fW0xeDu0WTcH5Gyn0kkwk1akLxDRG02SbRDzpYxvS0dAmg7qKoN1TP2Mt9RIKtjLqTr8ErzPkJoMP2po8AejwM4nr/q5oNwiTRuijyGc5yi92XKA+37xx4TcwexE3qMs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781121162; c=relaxed/simple; bh=Mwpfp4s7/oTgf4KgcwfIoaeKKHPtt+ET53lrSByUQBU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SD5Ugc9qFM/BRRF5QOwOnzWd9xa1VeJBb7I5QXoYXljqRYCxrTwsQ1VWHuOiNLjSyeRNr7+OVsU5AtwXjk6n+pLJ2jUeYq9fWA4ZZazJsPlcZcpUFU0GaHFQHcvXFpiciCcAAheJLVCxa23Gmki4wqaC+eWB6DLiJgCpeO1VssQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Bdg9I7n1; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Bdg9I7n1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 80A271F00898; Wed, 10 Jun 2026 19:52:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781121160; bh=MQlzc3tKjCiktDvlA46vQAC5Eprpnd3K2zunNpngdC8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Bdg9I7n1eSiMcwR/eXLfV++vqMdK4NmhkPPltIBjnNVGdAn1PDt7InkcLl2m6qqbL DioSCJzxid6x/xR1u053qTIALmmA0lyZUaSirCcuDd3zrIi29entF+1zoGsADc6XsT yY1hZiY/aDFJsUv7xR3lw3wLvnjzb28HaJ3g+l4nNySxwsNxZDXtmXQDzN5ymXQP1y gAGT2d7dK1jyAvIa2ie7b+/hHYkGW2DrwFOu+nsCeLdrescVPbQYf6YJ708dkOvuRR K55+UYWevIXHku8qiI1sn9S4LiYjxXHio7s2kWDv7qUC/adl+SZocRplypQQco4BtX f7mjpFLEILxXw== From: Arnaldo Carvalho de Melo To: Namhyung Kim Cc: Ingo Molnar , Thomas Gleixner , James Clark , Jiri Olsa , Ian Rogers , Adrian Hunter , Clark Williams , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Arnaldo Carvalho de Melo , sashiko-bot , Andi Kleen , "Claude Opus 4.6" Subject: [PATCH 07/23] perf intel-pt: Fix snprintf size tracking bug in insn decoder Date: Wed, 10 Jun 2026 16:51:40 -0300 Message-ID: <20260610195157.2091137-8-acme@kernel.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260610195157.2091137-1-acme@kernel.org> References: <20260610195157.2091137-1-acme@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 From: Arnaldo Carvalho de Melo dump_insn() tracks remaining buffer space with a 'left' variable, but the loop subtracts the cumulative offset 'n' each iteration instead of just the per-iteration delta: n += snprintf(x->out + n, left, "%02x ", inbuf[i]); left -= n; /* BUG: n is cumulative, not the delta */ After two iterations left goes massively negative, wrapping to a huge value when passed as size_t to snprintf(), disabling all bounds checking for the rest of the loop. Switch to scnprintf() accumulation using sizeof(x->out) - n as the remaining space, which is always correct and eliminates the separate 'left' variable entirely. Fixes: 48d02a1d5c137d36 ("perf script: Add 'brstackinsn' for branch stacks") Reported-by: sashiko-bot Cc: Adrian Hunter Cc: Andi Kleen Assisted-by: Claude Opus 4.6 Signed-off-by: Arnaldo Carvalho de Melo --- .../util/intel-pt-decoder/intel-pt-insn-decoder.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-) diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-insn-decoder.c b/tools/perf/util/intel-pt-decoder/intel-pt-insn-decoder.c index 72c7a4e15d617b60..f90fcbc4302df58f 100644 --- a/tools/perf/util/intel-pt-decoder/intel-pt-insn-decoder.c +++ b/tools/perf/util/intel-pt-decoder/intel-pt-insn-decoder.c @@ -220,7 +220,6 @@ const char *dump_insn(struct perf_insn *x, uint64_t ip __maybe_unused, { struct insn insn; int n, i, ret; - int left; ret = insn_decode(&insn, inbuf, inlen, x->is64bit ? INSN_MODE_64 : INSN_MODE_32); @@ -229,13 +228,9 @@ const char *dump_insn(struct perf_insn *x, uint64_t ip __maybe_unused, return ""; if (lenp) *lenp = insn.length; - left = sizeof(x->out); - n = snprintf(x->out, left, "insn: "); - left -= n; - for (i = 0; i < insn.length; i++) { - n += snprintf(x->out + n, left, "%02x ", inbuf[i]); - left -= n; - } + n = scnprintf(x->out, sizeof(x->out), "insn: "); + for (i = 0; i < insn.length; i++) + n += scnprintf(x->out + n, sizeof(x->out) - n, "%02x ", inbuf[i]); return x->out; } -- 2.54.0