tracing/probe: reject non-closed empty immediate strings

parse_probe_arg() accepts quoted immediate strings and passes the body
after the opening quote to __parse_imm_string(). That helper currently
computes strlen(str) and immediately dereferences str[len - 1], which
underflows when the body is empty and not closed with double-quotation.

Reject empty non-closed immediate strings before checking for the closing quote.

Link: https://lore.kernel.org/all/20260401160315.88518-1-pengpeng@iscas.ac.cn/
Fixes: a42e3c4de964 ("tracing/probe: Add immediate string parameter support")
Signed-off-by: Pengpeng Hou <pengpeng@iscas.ac.cn>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index e0a5dc86c07e971f0b77590158cd505a38943926..e1c73065dae51b4900c84c0299db02a6d5013cb5 100644 (file)
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -1068,7 +1068,7 @@ static int __parse_imm_string(char *str, char **pbuf, int offs)
 {
        size_t len = strlen(str);
 
-       if (str[len - 1] != '"') {
+       if (!len || str[len - 1] != '"') {
                trace_probe_log_err(offs + len, IMMSTR_NO_CLOSE);
                return -EINVAL;
        }