bpf, sockmap: Fix repeated calls to sock_put() when msg has more_data

[ 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: cfe4582096bd ("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>

diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index f69dcd3c7797a9b2f3ce993918013b4ae82d878b..229fa1f2b3815cacde56b79b7b8733bc3dc1512d 100644 (file)
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c
@@ -312,7 +312,7 @@ 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:
@@ -343,6 +343,7 @@ more_data:
        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: