From: Masami Hiramatsu (Google) Date: Mon, 20 Jul 2026 10:12:29 +0000 (+0900) Subject: tracing/probes: Fix potential underflow in LEN_OR_ZERO macro X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=8ce20bfba48902e1382187cd1a852f7cf3a1e739;p=thirdparty%2Fkernel%2Flinux.git tracing/probes: Fix potential underflow in LEN_OR_ZERO macro In __set_print_fmt(), LEN_OR_ZERO is defined as (len ? len - pos : 0). If len is non-zero but smaller than pos, len - pos evaluates to a negative integer. When passed as a size argument to snprintf(), this negative value is cast to a large unsigned size_t, bypassing buffer size limits. Ensure len > pos before subtracting to avoid integer underflow. Link: https://lore.kernel.org/all/178454234934.290363.15247317871499514139.stgit@devnote2/ Fixes: 5bf652aaf46c ("tracing/probes: Integrate duplicate set_print_fmt()") Cc: stable@vger.kernel.org Assisted-by: Antigravity:gemini-3.5-flash Signed-off-by: Masami Hiramatsu (Google) --- diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index 49daa3cc2a45..506e6037e163 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -2013,7 +2013,7 @@ int traceprobe_update_arg(struct probe_arg *arg) } /* When len=0, we just calculate the needed length */ -#define LEN_OR_ZERO (len ? len - pos : 0) +#define LEN_OR_ZERO (len > pos ? len - pos : 0) static int __set_print_fmt(struct trace_probe *tp, char *buf, int len, enum probe_print_type ptype) {