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Message-ID: <20240415150103.23316-1-shiming.cheng@mediatek.com>
Date: Mon, 15 Apr 2024 23:01:03 +0800
From: <shiming.cheng@...iatek.com>
To: <edumazet@...gle.com>, <davem@...emloft.net>, <kuba@...nel.org>,
<pabeni@...hat.com>, <matthias.bgg@...il.com>
CC: <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
<shiming.cheng@...iatek.com>, Lena Wang <lena.wang@...iatek.com>
Subject: [PATCH net] udp: fix segmentation crash for GRO packet without fraglist
From: Shiming Cheng <shiming.cheng@...iatek.com>
A GRO packet without fraglist is crashed and backtrace is as below:
[ 1100.812205][ C3] CPU: 3 PID: 0 Comm: swapper/3 Tainted:
G W OE 6.6.17-android15-0-g380371ea9bf1 #1
[ 1100.812317][ C3] __udp_gso_segment+0x298/0x4d4
[ 1100.812335][ C3] __skb_gso_segment+0xc4/0x120
[ 1100.812339][ C3] udp_rcv_segment+0x50/0x134
[ 1100.812344][ C3] udp_queue_rcv_skb+0x74/0x114
[ 1100.812348][ C3] udp_unicast_rcv_skb+0x94/0xac
[ 1100.812358][ C3] udp_rcv+0x20/0x30
The reason that the packet loses its fraglist is that in ingress bpf
it makes a test pull with to make sure it can read packet headers
via direct packet access: In bpf_progs/offload.c
try_make_writable -> bpf_skb_pull_data -> pskb_may_pull ->
__pskb_pull_tail This operation pull the data in fraglist into linear
and set the fraglist to null.
BPF needs to modify a proper length to do pull data. However kernel
should also improve the flow to avoid crash from a bpf function call.
As there is no split flow and app may not decode the merged UDP packet,
we should drop the packet without fraglist in skb_segment_list here.
Fixes: 3a1296a38d0c ("net: Support GRO/GSO fraglist chaining.")
Signed-off-by: Shiming Cheng <shiming.cheng@...iatek.com>
Signed-off-by: Lena Wang <lena.wang@...iatek.com>
---
net/core/skbuff.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index b99127712e67..f68f2679b086 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4504,6 +4504,9 @@ struct sk_buff *skb_segment_list(struct sk_buff *skb,
if (err)
goto err_linearize;
+ if (!list_skb)
+ goto err_linearize;
+
skb_shinfo(skb)->frag_list = NULL;
while (list_skb) {
--
2.18.0
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