linux-kernel - Re: [syzbot] Re: [syzbot] [bpf?] [net?] BUG: unable to handle kernel NULL pointer dereference in dev_map_hash_update

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Date: Tue, 27 Feb 2024 05:52:24 -0800
From: syzbot <syzbot+8cd36f6b65f3cafd400a@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] Re: [syzbot] [bpf?] [net?] BUG: unable to handle kernel
 NULL pointer dereference in dev_map_hash_update_elem

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Subject: Re: [syzbot] [bpf?] [net?] BUG: unable to handle kernel NULL pointer dereference in dev_map_hash_update_elem
Author: toke@...nel.org

#syz test

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index a936c704d4e7..9b2286f9c6da 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -130,13 +130,11 @@ static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
        bpf_map_init_from_attr(&dtab->map, attr);
 
        if (attr->map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
-               dtab->n_buckets = roundup_pow_of_two(dtab->map.max_entries);
-
-               if (!dtab->n_buckets) /* Overflow check */
+               if (dtab->map.max_entries > U32_MAX / 2)
                        return -EINVAL;
-       }
 
-       if (attr->map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
+               dtab->n_buckets = roundup_pow_of_two(dtab->map.max_entries);
+
                dtab->dev_index_head = dev_map_create_hash(dtab->n_buckets,
                                                           dtab->map.numa_node);
                if (!dtab->dev_index_head)