linux-kernel - [PATCH] lib/stackdepot: off by one in depot_fetch

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Date: Fri, 23 Feb 2024 17:20:13 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Andrey Konovalov <andreyknvl@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Potapenko <glider@...gle.com>,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] lib/stackdepot: off by one in depot_fetch_stack()

The stack_pools[] array has DEPOT_MAX_POOLS.  The "pools_num" tracks the
number of pools which are initialized.  See depot_init_pool() for more
details.

If pool_index == pools_num_cached, this will read one element beyond what
we want.  If not all the pools are initialized, then the pool will be
NULL, triggering a WARN(), and if they are all initialized it will read
one element beyond the end of the array.

Fixes: b29d31885814 ("lib/stackdepot: store free stack records in a freelist")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
>From static analysis.  What seems to have happened is that originally
we stored the highest index instead of the number of elements and when
we changed the > to >= comparison was overlooked.

 lib/stackdepot.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 8c795bb20afb..af6cc19a2003 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -447,7 +447,7 @@ static struct stack_record *depot_fetch_stack(depot_stack_handle_t handle)
 
 	lockdep_assert_not_held(&pool_lock);
 
-	if (pool_index > pools_num_cached) {
+	if (pool_index >= pools_num_cached) {
 		WARN(1, "pool index %d out of bounds (%d) for stack id %08x\n",
 		     pool_index, pools_num_cached, handle);
 		return NULL;
-- 
2.43.0