[PATCH 6.1 241/609] tracing/probes: Avoid temporary buffer truncation in trace_probe_match_command_args()

6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Masami Hiramatsu (Google) <[email protected]>

commit 15f197856d68882af9416fc97516bb55079b7677 upstream.

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: [email protected]
Assisted-by: Antigravity:gemini-3.5-flash
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 kernel/trace/trace_probe.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -1215,16 +1215,17 @@ int trace_probe_compare_arg_type(struct
 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;