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Wed, 28 Oct 2026 00:47:27 -0700 (PDT) Received: from localhost ([182.216.53.174]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3ae5a27f7c7sm1941127a91.2.2026.10.28.00.47.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Oct 2026 00:47:27 -0700 (PDT) From: Jaewon Jung To: Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Tom Zanussi , Namhyung Kim Cc: stable@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: [PATCH] tracing: Avoid undefined shifts for zero histogram map size Date: Wed, 28 Oct 2026 16:44:54 +0900 Message-ID: <20261028074610.2212374-1-jaewon8868@gmail.com> X-Mailer: git-send-email 2.43.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Reject size=0 before calling roundup_pow_of_two(). include/linux/log2.h documents roundup_pow_of_two() as: - the result is undefined when n == 0 With CONFIG_UBSAN_SHIFT=y, a size=0 histogram trigger reports: UBSAN: shift-out-of-bounds in include/linux/log2.h shift exponent 64 is too large for 64-bit type 'long unsigned int' Tested on x86_64 QEMU: size=0 is rejected without UBSAN warnings, and the histogram modifier and parser tests pass. Fixes: 7ef224d1d0e3 ("tracing: Add 'hist' event trigger command") Cc: stable@vger.kernel.org Signed-off-by: Jaewon Jung --- kernel/trace/trace_events_hist.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index f39fa8942673..3de794c7f5b2 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -1430,6 +1430,11 @@ static int parse_map_size(char *str) if (ret) goto out; + if (!size) { + ret = -EINVAL; + goto out; + } + map_bits = ilog2(roundup_pow_of_two(size)); if (map_bits < TRACING_MAP_BITS_MIN || map_bits > TRACING_MAP_BITS_MAX) -- 2.43.0