From: Andrew Kanner <andrew.kanner@gmail.com>
To: davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
pabeni@redhat.com, jasowang@redhat.com, netdev@vger.kernel.org,
brouer@redhat.com, linux-kernel@vger.kernel.org
Cc: syzbot+f817490f5bd20541b90a@syzkaller.appspotmail.com,
linux-kernel-mentees@lists.linuxfoundation.org
Subject: [PATCH 2/2] drivers: net: prevent tun_can_build_skb() to exceed xdp size limits
Date: Tue, 25 Jul 2023 01:13:26 +0300 [thread overview]
Message-ID: <20230724221326.384-2-andrew.kanner@gmail.com> (raw)
In-Reply-To: <20230724221326.384-1-andrew.kanner@gmail.com>
Tested with syzkaller repro with reduced packet size. It was
discovered that XDP_PACKET_HEADROOM is not checked in
tun_can_build_skb(), although pad may be incremented in
tun_build_skb().
Fixes: 7df13219d757 ("tun: reserve extra headroom only when XDP is set")
Link: https://syzkaller.appspot.com/text?tag=ReproC&x=12b2593ea80000
Signed-off-by: Andrew Kanner <andrew.kanner@gmail.com>
---
drivers/net/tun.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 18ccbbe9830a..cdf2bd85b383 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1582,7 +1582,13 @@ static void tun_rx_batched(struct tun_struct *tun, struct tun_file *tfile,
static bool tun_can_build_skb(struct tun_struct *tun, struct tun_file *tfile,
int len, int noblock, bool zerocopy, int *skb_xdp)
{
- if (SKB_DATA_ALIGN(len + TUN_RX_PAD) +
+ int pad = TUN_RX_PAD;
+ struct bpf_prog *xdp_prog = rcu_dereference(tun->xdp_prog);
+
+ if (xdp_prog)
+ pad += XDP_PACKET_HEADROOM;
+
+ if (SKB_DATA_ALIGN(len + pad) +
SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) > PAGE_SIZE) {
*skb_xdp = 0;
return false;
--
2.39.3
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next prev parent reply other threads:[~2023-07-24 22:15 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-24 22:13 [PATCH 1/2] drivers: net: use xdp only inside tun_build_skb() Andrew Kanner
2023-07-24 22:13 ` Andrew Kanner [this message]
2023-07-25 3:39 ` [PATCH 2/2] drivers: net: prevent tun_can_build_skb() to exceed xdp size limits Jason Wang
2023-07-25 10:49 ` Andrew Kanner
2023-07-25 3:28 ` [PATCH 1/2] drivers: net: use xdp only inside tun_build_skb() Jason Wang
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