tracing/probes: Avoid temporary buffer truncation in trace_probe_match_command_args()

In trace_probe_match_command_args(), a stack buffer buf[MAX_ARGSTR_LEN + 1]
(256 bytes) is used to format "<name>=<comm>". However, since name can
be up to 32 bytes (MAX_ARG_NAME_LEN) and comm up to 255 bytes
(MAX_ARGSTR_LEN), the formatted string can exceed 256 bytes and get
truncated by snprintf(), causing spurious argument matching failures.

Instead of formatting into a temporary buffer on stack, compare the
argument name, the '=' delimiter, and the comm expression directly.

Link: https://lore.kernel.org/all/178454233010.290363.10428767141343428804.stgit@devnote2/
Fixes: eb5bf81330a7 ("tracing/kprobe: Add per-probe delete from event")
Cc: stable@vger.kernel.org
Assisted-by: Antigravity:gemini-3.5-flash
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index d17cfee77d9cea337539ff44e3ec6a278f8aa5bf..95e3d072321fe49b47784eee6489ff744d1e99ec 100644 (file)
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -2338,16 +2338,17 @@ int trace_probe_compare_arg_type(struct trace_probe *a, struct trace_probe *b)
 bool trace_probe_match_command_args(struct trace_probe *tp,
                                    int argc, const char **argv)
 {
-       char buf[MAX_ARGSTR_LEN + 1];
        int i;
 
        if (tp->nr_args < argc)
                return false;
 
        for (i = 0; i < argc; i++) {
-               snprintf(buf, sizeof(buf), "%s=%s",
-                        tp->args[i].name, tp->args[i].comm);
-               if (strcmp(buf, argv[i]))
+               int len = strlen(tp->args[i].name);
+
+               if (strncmp(argv[i], tp->args[i].name, len) ||
+                   argv[i][len] != '=' ||
+                   strcmp(argv[i] + len + 1, tp->args[i].comm))
                        return false;
        }
        return true;