4.16-stable review patch. If anyone has any objections, please let me know.
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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(struct timer_list *t) { struct ccid2_hc_tx_sock *hc = from_timer(hc, t, tx_rtotimer); @@ -166,7 +176,7 @@ static void ccid2_hc_tx_rto_expire(struc
/* 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 @@ -232,6 +232,7 @@ static void dccp_write_xmitlet(unsigned else dccp_write_xmit(sk); bh_unlock_sock(sk); + sock_put(sk); }
static void dccp_write_xmit_timer(struct timer_list *t) @@ -240,7 +241,6 @@ static void dccp_write_xmit_timer(struct struct sock *sk = &dp->dccps_inet_connection.icsk_inet.sk;
dccp_write_xmitlet((unsigned long)sk); - sock_put(sk); }
void dccp_init_xmit_timers(struct sock *sk)