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Message-ID: <20241031122344.2148586-1-wangliang74@huawei.com>
Date: Thu, 31 Oct 2024 20:23:44 +0800
From: Wang Liang <wangliang74@...wei.com>
To: <edumazet@...gle.com>, <davem@...emloft.net>, <kuba@...nel.org>,
<pabeni@...hat.com>, <horms@...nel.org>, <dsahern@...nel.org>
CC: <yuehaibing@...wei.com>, <zhangchangzhong@...wei.com>,
<wangliang74@...wei.com>, <netdev@...r.kernel.org>,
<linux-kernel@...r.kernel.org>
Subject: [RFC PATCH net] net: fix data-races around sk->sk_forward_alloc
Syzkaller reported this warning:
[ 65.568203][ C0] ------------[ cut here ]------------
[ 65.569339][ C0] WARNING: CPU: 0 PID: 16 at net/ipv4/af_inet.c:156 inet_sock_destruct+0x1c5/0x1e0
[ 65.575017][ C0] Modules linked in:
[ 65.575699][ C0] CPU: 0 UID: 0 PID: 16 Comm: ksoftirqd/0 Not tainted 6.12.0-rc5 #26
[ 65.577086][ C0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
[ 65.577094][ C0] RIP: 0010:inet_sock_destruct+0x1c5/0x1e0
[ 65.577100][ C0] Code: 24 12 4c 89 e2 5b 48 c7 c7 98 ec bb 82 41 5c e9 d1 18 17 ff 4c 89 e6 5b 48 c7 c7 d0 ec bb 82 41 5c e9 bf 18 17 ff 0f 0b eb 83 <0f> 0b eb 97 0f 0b eb 87 0f 0b e9 68 ff ff ff 66 66 2e 0f 1f 84 00
[ 65.577107][ C0] RSP: 0018:ffffc9000008bd90 EFLAGS: 00010206
[ 65.577113][ C0] RAX: 0000000000000300 RBX: ffff88810b172a90 RCX: 0000000000000007
[ 65.577117][ C0] RDX: 0000000000000002 RSI: 0000000000000300 RDI: ffff88810b172a00
[ 65.577120][ C0] RBP: ffff88810b172a00 R08: ffff888104273c00 R09: 0000000000100007
[ 65.577123][ C0] R10: 0000000000020000 R11: 0000000000000006 R12: ffff88810b172a00
[ 65.577125][ C0] R13: 0000000000000004 R14: 0000000000000000 R15: ffff888237c31f78
[ 65.577131][ C0] FS: 0000000000000000(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000
[ 65.592485][ C0] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 65.592489][ C0] CR2: 00007ffc63fecac8 CR3: 000000000342e000 CR4: 00000000000006f0
[ 65.592491][ C0] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 65.592492][ C0] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 65.592495][ C0] Call Trace:
[ 65.596277][ C0] <TASK>
[ 65.598171][ C0] ? __warn+0x88/0x130
[ 65.598874][ C0] ? inet_sock_destruct+0x1c5/0x1e0
[ 65.598879][ C0] ? report_bug+0x18e/0x1a0
[ 65.598883][ C0] ? handle_bug+0x53/0x90
[ 65.598886][ C0] ? exc_invalid_op+0x18/0x70
[ 65.598888][ C0] ? asm_exc_invalid_op+0x1a/0x20
[ 65.598893][ C0] ? inet_sock_destruct+0x1c5/0x1e0
[ 65.598897][ C0] __sk_destruct+0x2a/0x200
[ 65.604664][ C0] rcu_do_batch+0x1aa/0x530
[ 65.605450][ C0] ? rcu_do_batch+0x13b/0x530
[ 65.605456][ C0] rcu_core+0x159/0x2f0
[ 65.605466][ C0] handle_softirqs+0xd3/0x2b0
[ 65.607689][ C0] ? __pfx_smpboot_thread_fn+0x10/0x10
[ 65.607695][ C0] run_ksoftirqd+0x25/0x30
[ 65.607699][ C0] smpboot_thread_fn+0xdd/0x1d0
[ 65.610152][ C0] kthread+0xd3/0x100
[ 65.610158][ C0] ? __pfx_kthread+0x10/0x10
[ 65.610160][ C0] ret_from_fork+0x34/0x50
[ 65.610170][ C0] ? __pfx_kthread+0x10/0x10
[ 65.610172][ C0] ret_from_fork_asm+0x1a/0x30
[ 65.610181][ C0] </TASK>
[ 65.610182][ C0] ---[ end trace 0000000000000000 ]---
Its possible that two threads call tcp_v6_do_rcv()/sk_forward_alloc_add()
concurrently when sk->sk_state == TCP_LISTEN with sk->sk_lock unlocked,
which triggers a data-race around sk->sk_forward_alloc:
tcp_v6_rcv
tcp_v6_do_rcv
skb_clone_and_charge_r
sk_rmem_schedule
__sk_mem_schedule
sk_forward_alloc_add()
skb_set_owner_r
sk_mem_charge
sk_forward_alloc_add()
__kfree_skb
skb_release_all
skb_release_head_state
sock_rfree
sk_mem_uncharge
sk_forward_alloc_add()
sk_mem_reclaim
// set local var reclaimable
__sk_mem_reclaim
sk_forward_alloc_add()
In this syzkaller testcase, two threads call tcp_v6_do_rcv() with
skb->truesize=768, the sk_forward_alloc changes like this:
(cpu 1) | (cpu 2) | sk_forward_alloc
... | ... | 0
__sk_mem_schedule() | | +4096 = 4096
| __sk_mem_schedule() | +4096 = 8192
sk_mem_charge() | | -768 = 7424
| sk_mem_charge() | -768 = 6656
... | ... |
sk_mem_uncharge() | | +768 = 7424
reclaimable=7424 | |
| sk_mem_uncharge() | +768 = 8192
| reclaimable=8192 |
__sk_mem_reclaim() | | -4096 = 4096
| __sk_mem_reclaim() | -8192 = -4096 != 0
Add lock around tcp_v6_do_rcv() in tcp_v6_rcv() will have some the
performance impacts, only add lock when opt_skb clone occurs. In some
scenes, tcp_v6_do_rcv() is embraced by sk->sk_lock, add
TCP_SKB_CB(skb)->sk_lock_capability to avoid re-locking.
Fixes: e994b2f0fb92 ("tcp: do not lock listener to process SYN packets")
Signed-off-by: Wang Liang <wangliang74@...wei.com>
---
include/net/tcp.h | 3 ++-
net/ipv6/tcp_ipv6.c | 21 ++++++++++++++++-----
2 files changed, 18 insertions(+), 6 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index d1948d357dad..110a23dda1eb 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -961,7 +961,8 @@ struct tcp_skb_cb {
__u8 txstamp_ack:1, /* Record TX timestamp for ack? */
eor:1, /* Is skb MSG_EOR marked? */
has_rxtstamp:1, /* SKB has a RX timestamp */
- unused:5;
+ sk_lock_capability:1, /* Avoid re-lock flag */
+ unused:4;
__u32 ack_seq; /* Sequence number ACK'd */
union {
struct {
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index d71ab4e1efe1..a1166035fbce 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1588,6 +1588,7 @@ int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
struct sk_buff *opt_skb = NULL;
enum skb_drop_reason reason;
struct tcp_sock *tp;
+ bool sk_lock_flag = false;
/* Imagine: socket is IPv6. IPv4 packet arrives,
goes to IPv4 receive handler and backlogged.
@@ -1618,8 +1619,13 @@ int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
by tcp. Feel free to propose better solution.
--ANK (980728)
*/
- if (np->rxopt.all)
+ if (np->rxopt.all) {
+ if (TCP_SKB_CB(skb)->sk_lock_capability) {
+ sk_lock_flag = true;
+ bh_lock_sock_nested(sk);
+ }
opt_skb = skb_clone_and_charge_r(skb, sk);
+ }
if (sk->sk_state == TCP_ESTABLISHED) { /* Fast path */
struct dst_entry *dst;
@@ -1641,7 +1647,7 @@ int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
tcp_rcv_established(sk, skb);
if (opt_skb)
goto ipv6_pktoptions;
- return 0;
+ goto unlock;
}
if (tcp_checksum_complete(skb))
@@ -1658,7 +1664,7 @@ int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
}
if (opt_skb)
__kfree_skb(opt_skb);
- return 0;
+ goto unlock;
}
} else
sock_rps_save_rxhash(sk, skb);
@@ -1668,7 +1674,7 @@ int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
goto reset;
if (opt_skb)
goto ipv6_pktoptions;
- return 0;
+ goto unlock;
reset:
tcp_v6_send_reset(sk, skb, sk_rst_convert_drop_reason(reason));
@@ -1676,7 +1682,7 @@ int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
if (opt_skb)
__kfree_skb(opt_skb);
sk_skb_reason_drop(sk, skb, reason);
- return 0;
+ goto unlock;
csum_err:
reason = SKB_DROP_REASON_TCP_CSUM;
trace_tcp_bad_csum(skb);
@@ -1715,6 +1721,9 @@ int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
}
consume_skb(opt_skb);
+unlock:
+ if (sk_lock_flag)
+ bh_unlock_sock(sk);
return 0;
}
@@ -1900,7 +1909,9 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
skb->dev = NULL;
if (sk->sk_state == TCP_LISTEN) {
+ TCP_SKB_CB(skb)->sk_lock_capability = true;
ret = tcp_v6_do_rcv(sk, skb);
+ TCP_SKB_CB(skb)->sk_lock_capability = false;
goto put_and_return;
}
--
2.34.1
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