[PATCH 10/12] perf jitdump: Validate debug entries on native (non-swap) path

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

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

The bounds-checking and nr_entry clamping added for the byte-swap path
only runs when jd->needs_bswap is true.  On native-endian files, nr_entry
passes through unvalidated to jit_repipe_debug_info(), which stores it
as jd->nr_debug_entries.  Downstream, jit_process_debug_info() in
genelf_debug.c iterates nr_debug_entries times via debug_entry_next(),
which calls strlen() on each entry's name field — a crafted nr_entry
causes OOB reads and writes.

Add bounds-checked iteration in jit_repipe_debug_info() that validates
each debug_entry fits in the payload and its name is NUL-terminated
before calling debug_entry_next().  Clamp nr_debug_entries to the count
of valid entries.

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
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/jitdump.c | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/jitdump.c b/tools/perf/util/jitdump.c
index 02840dbf8a1fc16c..87612ef3e232598e 100644
--- a/tools/perf/util/jitdump.c
+++ b/tools/perf/util/jitdump.c
@@ -694,8 +694,10 @@ static int jit_repipe_code_move(struct jit_buf_desc *jd, union jr_entry *jr)
 
 static int jit_repipe_debug_info(struct jit_buf_desc *jd, union jr_entry *jr)
 {
-	void *data;
-	size_t sz;
+	struct debug_entry *ent;
+	void *data, *end;
+	size_t sz, valid;
+	uint64_t i;
 
 	if (!(jd && jr))
 		return -1;
@@ -715,10 +717,25 @@ static int jit_repipe_debug_info(struct jit_buf_desc *jd, union jr_entry *jr)
 	jd->debug_data       = data;
 
 	/*
-	 * we must use nr_entry instead of size here because
-	 * we cannot distinguish actual entry from padding otherwise
+	 * Clamp nr_debug_entries to entries that actually fit in the
+	 * payload.  The byte-swap path already does this for cross-endian
+	 * files; validate on the native path too, since downstream
+	 * jit_process_debug_info() iterates via debug_entry_next() which
+	 * calls strlen() on each entry's name field.
 	 */
-	jd->nr_debug_entries = jr->info.nr_entry;
+	end = data + sz;
+	ent = data;
+	valid = 0;
+	for (i = 0; i < jr->info.nr_entry; i++) {
+		if ((void *)ent + sizeof(*ent) > end)
+			break;
+		/* name must be NUL-terminated within the payload */
+		if (!memchr(ent->name, '\0', (char *)end - ent->name))
+			break;
+		ent = debug_entry_next(ent);
+		valid++;
+	}
+	jd->nr_debug_entries = valid;
 
 	return 0;
 }
-- 
2.55.0