From: Daniel Borkmann <daniel@iogearbox.net>
To: xiakaixu1987@gmail.com, ast@kernel.org, kafai@fb.com,
songliubraving@fb.com, yhs@fb.com, andrii@kernel.org,
john.fastabend@gmail.com, kpsingh@chromium.org
Cc: netdev@vger.kernel.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org, Kaixu Xia <kaixuxia@tencent.com>,
dsahern@gmail.com
Subject: Re: [PATCH] bpf: Check the return value of dev_get_by_index_rcu()
Date: Fri, 20 Nov 2020 16:13:22 +0100 [thread overview]
Message-ID: <65d8f988-5b41-24c2-8501-7cbbddb1238e@iogearbox.net> (raw)
In-Reply-To: <1605769468-2078-1-git-send-email-kaixuxia@tencent.com>
[ +David ]
On 11/19/20 8:04 AM, xiakaixu1987@gmail.com wrote:
> From: Kaixu Xia <kaixuxia@tencent.com>
>
> The return value of dev_get_by_index_rcu() can be NULL, so here it
> is need to check the return value and return error code if it is NULL.
>
> Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
> ---
> net/core/filter.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 2ca5eecebacf..1263fe07170a 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -5573,6 +5573,8 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb,
> struct net_device *dev;
>
> dev = dev_get_by_index_rcu(net, params->ifindex);
> + if (unlikely(!dev))
> + return -EINVAL;
> if (!is_skb_forwardable(dev, skb))
> rc = BPF_FIB_LKUP_RET_FRAG_NEEDED;
The above logic is quite ugly anyway given we fetched the dev pointer already earlier
in bpf_ipv{4,6}_fib_lookup() and now need to redo it again ... so yeah there could be
a tiny race in here. We wanted do bring this logic closer to what XDP does anyway,
something like below, for example. David, thoughts? Thx
Subject: [PATCH] diff mtu check
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
net/core/filter.c | 22 +++++-----------------
1 file changed, 5 insertions(+), 17 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index 2ca5eecebacf..3bab0a97fa38 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5547,9 +5547,6 @@ static const struct bpf_func_proto bpf_xdp_fib_lookup_proto = {
BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb,
struct bpf_fib_lookup *, params, int, plen, u32, flags)
{
- struct net *net = dev_net(skb->dev);
- int rc = -EAFNOSUPPORT;
-
if (plen < sizeof(*params))
return -EINVAL;
@@ -5559,25 +5556,16 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb,
switch (params->family) {
#if IS_ENABLED(CONFIG_INET)
case AF_INET:
- rc = bpf_ipv4_fib_lookup(net, params, flags, false);
- break;
+ return bpf_ipv4_fib_lookup(dev_net(skb->dev), params, flags,
+ !skb_is_gso(skb));
#endif
#if IS_ENABLED(CONFIG_IPV6)
case AF_INET6:
- rc = bpf_ipv6_fib_lookup(net, params, flags, false);
- break;
+ return bpf_ipv6_fib_lookup(dev_net(skb->dev), params, flags,
+ !skb_is_gso(skb));
#endif
}
-
- if (!rc) {
- struct net_device *dev;
-
- dev = dev_get_by_index_rcu(net, params->ifindex);
- if (!is_skb_forwardable(dev, skb))
- rc = BPF_FIB_LKUP_RET_FRAG_NEEDED;
- }
-
- return rc;
+ return -EAFNOSUPPORT;
}
static const struct bpf_func_proto bpf_skb_fib_lookup_proto = {
--
2.21.0
next prev parent reply other threads:[~2020-11-20 15:13 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-19 7:04 [PATCH] bpf: Check the return value of dev_get_by_index_rcu() xiakaixu1987
2020-11-20 15:13 ` Daniel Borkmann [this message]
2020-11-20 15:19 ` David Ahern
2020-11-20 16:01 ` Daniel Borkmann
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