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For $arg0, n is 0 so the index is -1. Because ctx->nr_params is signed, the "idx >= nr_params" guard in sprint_nth_btf_arg() does not catch the negative index, and ctx->params[-1].name_off is read out of bounds. The normal per-argument path (parse_probe_vars()) already rejects $arg0 via its argument-number check, but meta-argument expansion runs before per-argument parsing and substitutes the value first, bypassing that check. Reject $arg0 explicitly during expansion. Fixes: 18b1e870a496 ("tracing/probes: Add $arg* meta argument for all function args") Signed-off-by: Raushan Patel --- kernel/trace/trace_probe.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index 506e6037e163..c8fd9b946f44 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -1901,7 +1901,11 @@ const char **traceprobe_expand_meta_args(int argc, const char *argv[], trace_probe_log_err(0, BAD_VAR); return ERR_PTR(-ENOENT); } - /* Note: $argN starts from $arg1 */ + /* Note: $argN starts from $arg1, so $arg0 is invalid. */ + if (n == 0) { + trace_probe_log_err(0, BAD_ARG_NUM); + return ERR_PTR(-EINVAL); + } ret = sprint_nth_btf_arg(n - 1, type, buf + used, bufsize - used, ctx); if (ret < 0) -- 2.53.0