linux-kernel - [RFC PATCH v2 1/2] lib, stackdepot: check stackdepot handle before accessing slabs.

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Message-Id: <20210902000154.1096484-2-imran.f.khan@oracle.com>
Date:   Thu,  2 Sep 2021 10:01:53 +1000
From:   Imran Khan <imran.f.khan@...cle.com>
To:     vbabka@...e.cz, geert@...ux-m68k.org, akpm@...ux-foundation.org,
        ryabinin.a.a@...il.com, glider@...gle.com, andreyknvl@...il.com,
        dvyukov@...gle.com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v2 1/2] lib, stackdepot: check stackdepot handle before accessing slabs.

stack_depot_save allocates slabs that will be used for storing
objects in future.If this slab allocation fails we may get to
a situation where space allocation for a new stack_record fails,
causing stack_depot_save to return 0 as handle.
If user of this handle ends up invoking stack_depot_fetch with
this handle value, current implementation of stack_depot_fetch
will end up using slab from wrong index.
To avoid this check handle value at the beginning.

Signed-off-by: Imran Khan <imran.f.khan@...cle.com>
Suggested-by: Vlastimil Babka <vbabka@...e.cz>
---
 lib/stackdepot.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 0a2e417f83cb..67439c082490 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -232,6 +232,9 @@ unsigned int stack_depot_fetch(depot_stack_handle_t handle,
 	struct stack_record *stack;
 
 	*entries = NULL;
+	if (!handle)
+		return 0;
+
 	if (parts.slabindex > depot_index) {
 		WARN(1, "slab index %d out of bounds (%d) for stack id %08x\n",
 			parts.slabindex, depot_index, handle);
-- 
2.30.2