[PATCH 4.9 03/33] dccp: fix tasklet usage

Greg Kroah-Hartman
2018-05-18T08:15:42Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit a8d7aa17bbc970971ccdf71988ea19230ab368b1 ]

syzbot reported a crash in tasklet_action_common() caused by dccp.

dccp needs to make sure socket wont disappear before tasklet handler
has completed.

This patch takes a reference on the socket when arming the tasklet,
and moves the sock_put() from dccp_write_xmit_timer() to dccp_write_xmitlet()

kernel BUG at kernel/softirq.c:514!
invalid opcode: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 17 Comm: ksoftirqd/1 Not tainted 4.17.0-rc3+ #30
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:tasklet_action_common.isra.19+0x6db/0x700 kernel/softirq.c:515
RSP: 0018:ffff8801d9b3faf8 EFLAGS: 00010246
dccp_close: ABORT with 65423 bytes unread
RAX: 1ffff1003b367f6b RBX: ffff8801daf1f3f0 RCX: 0000000000000000
RDX: ffff8801cf895498 RSI: 0000000000000004 RDI: 0000000000000000
RBP: ffff8801d9b3fc40 R08: ffffed0039f12a95 R09: ffffed0039f12a94
dccp_close: ABORT with 65423 bytes unread
R10: ffffed0039f12a94 R11: ffff8801cf8954a3 R12: 0000000000000000
R13: ffff8801d9b3fc18 R14: dffffc0000000000 R15: ffff8801cf895490
FS: 0000000000000000(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2bc28000 CR3: 00000001a08a9000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
tasklet_action+0x1d/0x20 kernel/softirq.c:533
__do_softirq+0x2e0/0xaf5 kernel/softirq.c:285
dccp_close: ABORT with 65423 bytes unread
run_ksoftirqd+0x86/0x100 kernel/softirq.c:646
smpboot_thread_fn+0x417/0x870 kernel/smpboot.c:164
kthread+0x345/0x410 kernel/kthread.c:238
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
Code: 48 8b 85 e8 fe ff ff 48 8b 95 f0 fe ff ff e9 94 fb ff ff 48 89 95 f0 fe ff ff e8 81 53 6e 00 48 8b 95 f0 fe ff ff e9 62 fb ff ff <0f> 0b 48 89 cf 48 89 8d e8 fe ff ff e8 64 53 6e 00 48 8b 8d e8
RIP: tasklet_action_common.isra.19+0x6db/0x700 kernel/softirq.c:515 RSP: ffff8801d9b3faf8

Fixes: dc841e30eaea ("dccp: Extend CCID packet dequeueing interface")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Cc: dccp@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/dccp/ccids/ccid2.c | 14 ++++++++++++--
net/dccp/timer.c | 2 +-
2 files changed, 13 insertions(+), 3 deletions(-)

--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -126,6 +126,16 @@ static void ccid2_change_l_seq_window(st
DCCPF_SEQ_WMAX));
}

+static void dccp_tasklet_schedule(struct sock *sk)
+{
+ struct tasklet_struct *t = &dccp_sk(sk)->dccps_xmitlet;
+
+ if (!test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
+ sock_hold(sk);
+ __tasklet_schedule(t);
+ }
+}
+
static void ccid2_hc_tx_rto_expire(unsigned long data)
{
struct sock *sk = (struct sock *)data;
@@ -166,7 +176,7 @@ static void ccid2_hc_tx_rto_expire(unsig

/* if we were blocked before, we may now send cwnd=1 packet */
if (sender_was_blocked)
- tasklet_schedule(&dccp_sk(sk)->dccps_xmitlet);
+ dccp_tasklet_schedule(sk);
/* restart backed-off timer */
sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
out:
@@ -706,7 +716,7 @@ static void ccid2_hc_tx_packet_recv(stru
done:
/* check if incoming Acks allow pending packets to be sent */
if (sender_was_blocked && !ccid2_cwnd_network_limited(hc))
- tasklet_schedule(&dccp_sk(sk)->dccps_xmitlet);
+ dccp_tasklet_schedule(sk);
dccp_ackvec_parsed_cleanup(&hc->tx_av_chunks);
}

--- a/net/dccp/timer.c
+++ b/net/dccp/timer.c
@@ -230,12 +230,12 @@ static void dccp_write_xmitlet(unsigned
else
dccp_write_xmit(sk);
bh_unlock_sock(sk);
+ sock_put(sk);
}

static void dccp_write_xmit_timer(unsigned long data)
{
dccp_write_xmitlet(data);
- sock_put((struct sock *)data);
}

void dccp_init_xmit_timers(struct sock *sk)