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Message-ID: <20250227082642.2461118-1-edumazet@google.com>
Date: Thu, 27 Feb 2025 08:26:42 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Andrew Lunn <andrew+netdev@...n.ch>
Cc: Simon Horman <horms@...nel.org>, netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>, syzbot+da65c993ae113742a25f@...kaller.appspotmail.com
Subject: [PATCH net] llc: do not use skb_get() before dev_queue_xmit()
syzbot is able to crash hosts [1], using llc and devices
not supporting IFF_TX_SKB_SHARING.
In this case, e1000 driver calls eth_skb_pad(), while
the skb is shared.
Simply replace skb_get() by skb_clone() in net/llc/llc_s_ac.c
Note that e1000 driver might have an issue with pktgen,
because it does not clear IFF_TX_SKB_SHARING, this is an
orthogonal change.
We need to audit other skb_get() uses in net/llc.
[1]
kernel BUG at net/core/skbuff.c:2178 !
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 16371 Comm: syz.2.2764 Not tainted 6.14.0-rc4-syzkaller-00052-gac9c34d1e45a #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:pskb_expand_head+0x6ce/0x1240 net/core/skbuff.c:2178
Call Trace:
<TASK>
__skb_pad+0x18a/0x610 net/core/skbuff.c:2466
__skb_put_padto include/linux/skbuff.h:3843 [inline]
skb_put_padto include/linux/skbuff.h:3862 [inline]
eth_skb_pad include/linux/etherdevice.h:656 [inline]
e1000_xmit_frame+0x2d99/0x5800 drivers/net/ethernet/intel/e1000/e1000_main.c:3128
__netdev_start_xmit include/linux/netdevice.h:5151 [inline]
netdev_start_xmit include/linux/netdevice.h:5160 [inline]
xmit_one net/core/dev.c:3806 [inline]
dev_hard_start_xmit+0x9a/0x7b0 net/core/dev.c:3822
sch_direct_xmit+0x1ae/0xc30 net/sched/sch_generic.c:343
__dev_xmit_skb net/core/dev.c:4045 [inline]
__dev_queue_xmit+0x13d4/0x43e0 net/core/dev.c:4621
dev_queue_xmit include/linux/netdevice.h:3313 [inline]
llc_sap_action_send_test_c+0x268/0x320 net/llc/llc_s_ac.c:144
llc_exec_sap_trans_actions net/llc/llc_sap.c:153 [inline]
llc_sap_next_state net/llc/llc_sap.c:182 [inline]
llc_sap_state_process+0x239/0x510 net/llc/llc_sap.c:209
llc_ui_sendmsg+0xd0d/0x14e0 net/llc/af_llc.c:993
sock_sendmsg_nosec net/socket.c:718 [inline]
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: syzbot+da65c993ae113742a25f@...kaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/67c020c0.050a0220.222324.0011.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
net/llc/llc_s_ac.c | 49 +++++++++++++++++++++++++---------------------
1 file changed, 27 insertions(+), 22 deletions(-)
diff --git a/net/llc/llc_s_ac.c b/net/llc/llc_s_ac.c
index 06fb8e6944b06aecad73739bc9337e551cf73a90..7a0cae9a8111488979ce1c22bcc7ed86ccee5269 100644
--- a/net/llc/llc_s_ac.c
+++ b/net/llc/llc_s_ac.c
@@ -24,7 +24,7 @@
#include <net/llc_s_ac.h>
#include <net/llc_s_ev.h>
#include <net/llc_sap.h>
-
+#include <net/sock.h>
/**
* llc_sap_action_unitdata_ind - forward UI PDU to network layer
@@ -40,6 +40,26 @@ int llc_sap_action_unitdata_ind(struct llc_sap *sap, struct sk_buff *skb)
return 0;
}
+static int llc_prepare_and_xmit(struct sk_buff *skb)
+{
+ struct llc_sap_state_ev *ev = llc_sap_ev(skb);
+ struct sk_buff *nskb;
+ int rc;
+
+ rc = llc_mac_hdr_init(skb, ev->saddr.mac, ev->daddr.mac);
+ if (rc)
+ return rc;
+
+ nskb = skb_clone(skb, GFP_ATOMIC);
+ if (!nskb)
+ return -ENOMEM;
+
+ if (skb->sk)
+ skb_set_owner_w(nskb, skb->sk);
+
+ return dev_queue_xmit(nskb);
+}
+
/**
* llc_sap_action_send_ui - sends UI PDU resp to UNITDATA REQ to MAC layer
* @sap: SAP
@@ -52,17 +72,12 @@ int llc_sap_action_unitdata_ind(struct llc_sap *sap, struct sk_buff *skb)
int llc_sap_action_send_ui(struct llc_sap *sap, struct sk_buff *skb)
{
struct llc_sap_state_ev *ev = llc_sap_ev(skb);
- int rc;
llc_pdu_header_init(skb, LLC_PDU_TYPE_U, ev->saddr.lsap,
ev->daddr.lsap, LLC_PDU_CMD);
llc_pdu_init_as_ui_cmd(skb);
- rc = llc_mac_hdr_init(skb, ev->saddr.mac, ev->daddr.mac);
- if (likely(!rc)) {
- skb_get(skb);
- rc = dev_queue_xmit(skb);
- }
- return rc;
+
+ return llc_prepare_and_xmit(skb);
}
/**
@@ -77,17 +92,12 @@ int llc_sap_action_send_ui(struct llc_sap *sap, struct sk_buff *skb)
int llc_sap_action_send_xid_c(struct llc_sap *sap, struct sk_buff *skb)
{
struct llc_sap_state_ev *ev = llc_sap_ev(skb);
- int rc;
llc_pdu_header_init(skb, LLC_PDU_TYPE_U_XID, ev->saddr.lsap,
ev->daddr.lsap, LLC_PDU_CMD);
llc_pdu_init_as_xid_cmd(skb, LLC_XID_NULL_CLASS_2, 0);
- rc = llc_mac_hdr_init(skb, ev->saddr.mac, ev->daddr.mac);
- if (likely(!rc)) {
- skb_get(skb);
- rc = dev_queue_xmit(skb);
- }
- return rc;
+
+ return llc_prepare_and_xmit(skb);
}
/**
@@ -133,17 +143,12 @@ int llc_sap_action_send_xid_r(struct llc_sap *sap, struct sk_buff *skb)
int llc_sap_action_send_test_c(struct llc_sap *sap, struct sk_buff *skb)
{
struct llc_sap_state_ev *ev = llc_sap_ev(skb);
- int rc;
llc_pdu_header_init(skb, LLC_PDU_TYPE_U, ev->saddr.lsap,
ev->daddr.lsap, LLC_PDU_CMD);
llc_pdu_init_as_test_cmd(skb);
- rc = llc_mac_hdr_init(skb, ev->saddr.mac, ev->daddr.mac);
- if (likely(!rc)) {
- skb_get(skb);
- rc = dev_queue_xmit(skb);
- }
- return rc;
+
+ return llc_prepare_and_xmit(skb);
}
int llc_sap_action_send_test_r(struct llc_sap *sap, struct sk_buff *skb)
--
2.48.1.658.g4767266eb4-goog
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