[PATCH 6.0 0430/1073] bpf, sockmap: Fix repeated calls to sock_put() when msg has more_data

Greg Kroah-Hartman
2022-12-28T15:50:00Z

From: Pengcheng Yang <yangpc@wangsu.com>

[ Upstream commit 7a9841ca025275b5b0edfb0b618934abb6ceec15 ]

In tcp_bpf_send_verdict() redirection, the eval variable is assigned to
__SK_REDIRECT after the apply_bytes data is sent, if msg has more_data,
sock_put() will be called multiple times.

We should reset the eval variable to __SK_NONE every time more_data
starts.

This causes:

IPv4: Attempt to release TCP socket in state 1 00000000b4c925d7
------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 5 PID: 4482 at lib/refcount.c:25 refcount_warn_saturate+0x7d/0x110
Modules linked in:
CPU: 5 PID: 4482 Comm: sockhash_bypass Kdump: loaded Not tainted 6.0.0 #1
Hardware name: Red Hat KVM, BIOS 1.11.0-2.el7 04/01/2014
Call Trace:
<TASK>
__tcp_transmit_skb+0xa1b/0xb90
? __alloc_skb+0x8c/0x1a0
? __kmalloc_node_track_caller+0x184/0x320
tcp_write_xmit+0x22a/0x1110
__tcp_push_pending_frames+0x32/0xf0
do_tcp_sendpages+0x62d/0x640
tcp_bpf_push+0xae/0x2c0
tcp_bpf_sendmsg_redir+0x260/0x410
? preempt_count_add+0x70/0xa0
tcp_bpf_send_verdict+0x386/0x4b0
tcp_bpf_sendmsg+0x21b/0x3b0
sock_sendmsg+0x58/0x70
__sys_sendto+0xfa/0x170
? xfd_validate_state+0x1d/0x80
? switch_fpu_return+0x59/0xe0
__x64_sys_sendto+0x24/0x30
do_syscall_64+0x37/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fixes: cd9733f5d75c ("tcp_bpf: Fix one concurrency problem in the tcp_bpf_send_verdict function")
Signed-off-by: Pengcheng Yang <yangpc@wangsu.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/1669718441-2654-2-git-send-email-yangpc@wangsu.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/tcp_bpf.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index cf9c3e8f7ccb..f3e868f4cd9e 100644
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c
@@ -279,7 +279,7 @@ static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock,
bool cork = false, enospc = sk_msg_full(msg);
struct sock *sk_redir;
u32 tosend, origsize, sent, delta = 0;
- u32 eval = __SK_NONE;
+ u32 eval;
int ret;

more_data:
@@ -310,6 +310,7 @@ static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock,
tosend = msg->sg.size;
if (psock->apply_bytes && psock->apply_bytes < tosend)
tosend = psock->apply_bytes;
+ eval = __SK_NONE;

switch (psock->eval) {
case __SK_PASS:
--
2.35.1