[PATCH 11/12] perf jitdump: Validate sym string NUL-termination in code load

[Arnaldo Carvalho de Melo <acme@kernel.org>]

From: Arnaldo Carvalho de Melo <acme@redhat.com>

jit_repipe_code_load() computes sym = (void *)jr + sizeof(jr->load) and
passes it to jit_emit_elf() which calls strlen(sym) via jit_write_elf().
If code_size equals total_size - sizeof(jr->load), the sym pointer
aliases the code blob with no NUL terminator, and strlen() scans past
the buffer into adjacent heap memory.

Add a memchr() check to verify the symbol name is NUL-terminated within
the region between the load header and the code blob before use.

Fixes: 598b7c6919c7bbcc ("perf jit: add source line info support")
Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Assisted-by: Claude:claude-opus-4.6
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/jitdump.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/perf/util/jitdump.c b/tools/perf/util/jitdump.c
index 5a3ea2681fb37105..5898a7d8eb962daf 100644
--- a/tools/perf/util/jitdump.c
+++ b/tools/perf/util/jitdump.c
@@ -487,6 +487,13 @@ static int jit_repipe_code_load(struct jit_buf_desc *jd, union jr_entry *jr)
 
 	sym   = (void *)((unsigned long)jr + sizeof(jr->load));
 	code  = (unsigned long)jr + jr->load.p.total_size - csize;
+
+	/* sym string lives between the load header and the code blob */
+	if (!memchr(sym, '\0', code - (unsigned long)sym)) {
+		pr_warning("jitdump: unterminated symbol name in code_load record\n");
+		return -1;
+	}
+
 	count = jr->load.code_index;
 	idr_size = jd->machine->id_hdr_size;
 
-- 
2.55.0