linux-kernel - [PATCH v2 2/2] lib: stackdepot: Avoid null pointer if stack_depot

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Message-ID: <20241116002322.1035417-2-jstultz@google.com>
Date: Fri, 15 Nov 2024 16:23:07 -0800
From: John Stultz <jstultz@...gle.com>
To: LKML <linux-kernel@...r.kernel.org>
Cc: John Stultz <jstultz@...gle.com>, Steven Rostedt <rostedt@...dmis.org>, 
	Alexander Potapenko <glider@...gle.com>, Andrey Konovalov <andreyknvl@...il.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, kernel-team@...roid.com
Subject: [PATCH v2 2/2] lib: stackdepot: Avoid null pointer if
 stack_depot_save is called too early

If stack_depot_save is called before stackdepot has initialized
a null reference to the stack_table might be used, crashing the
system.

Instead, check stack_table has been initialized before going
further.

Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Alexander Potapenko <glider@...gle.com>
Cc: Andrey Konovalov <andreyknvl@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: kernel-team@...roid.com
Signed-off-by: John Stultz <jstultz@...gle.com>
---
 lib/stackdepot.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 5ed34cc963fc..09780c835362 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -611,6 +611,9 @@ depot_stack_handle_t stack_depot_save_flags(unsigned long *entries,
 	if (unlikely(nr_entries == 0) || stack_depot_disabled)
 		return 0;
 
+	if (!stack_table)
+		return 0;
+
 	hash = hash_stack(entries, nr_entries);
 	bucket = &stack_table[hash & stack_hash_mask];
 
-- 
2.47.0.338.g60cca15819-goog