linux-kernel - [PATCH 5.4 129/155] bpf: Initialize storage pointers to NULL to prevent freeing garbage pointer

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Message-Id: <20200331085432.766853128@linuxfoundation.org>
Date:   Tue, 31 Mar 2020 10:59:29 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Andrii Nakryiko <andriin@...com>,
        Alexei Starovoitov <ast@...nel.org>
Subject: [PATCH 5.4 129/155] bpf: Initialize storage pointers to NULL to prevent freeing garbage pointer

From: Andrii Nakryiko <andriin@...com>

commit 62039c30c19dcab96621e074aeeb90da7100def7 upstream.

Local storage array isn't initialized, so if cgroup storage allocation fails
for BPF_CGROUP_STORAGE_SHARED, error handling code will attempt to free
uninitialized pointer for BPF_CGROUP_STORAGE_PERCPU storage type. Avoid this
by always initializing storage pointers to NULLs.

Fixes: 8bad74f9840f ("bpf: extend cgroup bpf core to allow multiple cgroup storage types")
Signed-off-by: Andrii Nakryiko <andriin@...com>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Link: https://lore.kernel.org/bpf/20200309222756.1018737-1-andriin@fb.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/bpf/cgroup.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -303,8 +303,8 @@ int __cgroup_bpf_attach(struct cgroup *c
 {
 	struct list_head *progs = &cgrp->bpf.progs[type];
 	struct bpf_prog *old_prog = NULL;
-	struct bpf_cgroup_storage *storage[MAX_BPF_CGROUP_STORAGE_TYPE],
-		*old_storage[MAX_BPF_CGROUP_STORAGE_TYPE] = {NULL};
+	struct bpf_cgroup_storage *storage[MAX_BPF_CGROUP_STORAGE_TYPE] = {};
+	struct bpf_cgroup_storage *old_storage[MAX_BPF_CGROUP_STORAGE_TYPE] = {};
 	enum bpf_cgroup_storage_type stype;
 	struct bpf_prog_list *pl;
 	bool pl_was_allocated;