netdev - [PATCH] bpf: Check for integer overflow when using roundup_pow_of

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Date:   Wed, 27 Jan 2021 06:36:53 +0000
From:   Bui Quang Minh <minhquangbui99@...il.com>
To:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        kafai@...com, songliubraving@...com, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org, davem@...emloft.net
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, minhquangbui99@...il.com
Subject: [PATCH] bpf: Check for integer overflow when using roundup_pow_of_two()

On 32-bit architecture, roundup_pow_of_two() can return 0 when the argument
has upper most bit set due to resulting 1UL << 32. Add a check for this
case.

Fixes: d5a3b1f ("bpf: introduce BPF_MAP_TYPE_STACK_TRACE")
Signed-off-by: Bui Quang Minh <minhquangbui99@...il.com>
---
 kernel/bpf/stackmap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index aea96b638473..bfafbf115bf3 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -115,6 +115,8 @@ static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
 
 	/* hash table size must be power of 2 */
 	n_buckets = roundup_pow_of_two(attr->max_entries);
+	if (!n_buckets)
+		return ERR_PTR(-E2BIG);
 
 	cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
 	cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
-- 
2.17.1