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Message-ID: <CACGkMEtZRgs5Ou9qNGJ2aQt9yUxywL4Ob0WkpHPXHq=Sxqi3mw@mail.gmail.com> Date: Fri, 23 Sep 2022 11:23:13 +0800 From: Jason Wang <jasowang@...hat.com> To: "liujian (CE)" <liujian56@...wei.com> Cc: "me@...i.io" <me@...i.io>, davem <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>, netdev <netdev@...r.kernel.org> Subject: Re: [PATCH net v2] tun: Check tun device queue status in tun_chr_write_iter On Thu, Sep 22, 2022 at 9:45 PM liujian (CE) <liujian56@...wei.com> wrote: > > > > > -----Original Message----- > > From: liujian (CE) > > Sent: Friday, September 16, 2022 3:05 PM > > To: 'Jason Wang' <jasowang@...hat.com> > > Cc: davem <davem@...emloft.net>; Eric Dumazet > > <edumazet@...gle.com>; Jakub Kicinski <kuba@...nel.org>; Paolo Abeni > > <pabeni@...hat.com>; Alexei Starovoitov <ast@...nel.org>; Daniel > > Borkmann <daniel@...earbox.net>; Jesper Dangaard Brouer > > <hawk@...nel.org>; John Fastabend <john.fastabend@...il.com>; netdev > > <netdev@...r.kernel.org> > > Subject: RE: [PATCH net v2] tun: Check tun device queue status in > > tun_chr_write_iter > > > > > > > > > -----Original Message----- > > > From: Jason Wang [mailto:jasowang@...hat.com] > > > Sent: Friday, September 16, 2022 9:57 AM > > > To: liujian (CE) <liujian56@...wei.com> > > > Cc: davem <davem@...emloft.net>; Eric Dumazet > > <edumazet@...gle.com>; > > > Jakub Kicinski <kuba@...nel.org>; Paolo Abeni <pabeni@...hat.com>; > > > Alexei Starovoitov <ast@...nel.org>; Daniel Borkmann > > > <daniel@...earbox.net>; Jesper Dangaard Brouer <hawk@...nel.org>; > > John > > > Fastabend <john.fastabend@...il.com>; netdev > > <netdev@...r.kernel.org> > > > Subject: Re: [PATCH net v2] tun: Check tun device queue status in > > > tun_chr_write_iter > > > > > > On Thu, Sep 15, 2022 at 8:34 PM Liu Jian <liujian56@...wei.com> wrote: > > > > > > > > syzbot found below warning: > > > > > > > > ------------[ cut here ]------------ > > > > geneve0 received packet on queue 3, but number of RX queues is 3 > > > > WARNING: CPU: 1 PID: 29734 at net/core/dev.c:4611 netif_get_rxqueue > > > > net/core/dev.c:4611 [inline] > > > > WARNING: CPU: 1 PID: 29734 at net/core/dev.c:4611 > > > > netif_receive_generic_xdp+0xb10/0xb50 net/core/dev.c:4683 Modules > > > linked in: > > > > CPU: 1 PID: 29734 Comm: syz-executor.0 Not tainted 5.10.0 #5 > > > > Hardware > > > > name: linux,dummy-virt (DT) > > > > pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=--) pc : > > > > netif_get_rxqueue net/core/dev.c:4611 [inline] pc : > > > > netif_receive_generic_xdp+0xb10/0xb50 net/core/dev.c:4683 lr : > > > > netif_get_rxqueue net/core/dev.c:4611 [inline] lr : > > > > netif_receive_generic_xdp+0xb10/0xb50 net/core/dev.c:4683 sp : > > > > ffffa00016127770 > > > > x29: ffffa00016127770 x28: ffff3f4607d6acb4 > > > > x27: ffff3f4607d6acb0 x26: ffff3f4607d6ad20 > > > > x25: ffff3f461de3c000 x24: ffff3f4607d6ad28 > > > > x23: ffffa00010059000 x22: ffff3f4608719100 > > > > x21: 0000000000000003 x20: ffffa000161278a0 > > > > x19: ffff3f4607d6ac40 x18: 0000000000000000 > > > > x17: 0000000000000000 x16: 00000000f2f2f204 > > > > x15: 00000000f2f20000 x14: 6465766965636572 > > > > x13: 20306576656e6567 x12: ffff98b8ed3b924d > > > > x11: 1ffff8b8ed3b924c x10: ffff98b8ed3b924c > > > > x9 : ffffc5c76525c9c4 x8 : 0000000000000000 > > > > x7 : 0000000000000001 x6 : ffff98b8ed3b924c > > > > x5 : ffff3f460f3b29c0 x4 : dfffa00000000000 > > > > x3 : ffffc5c765000000 x2 : 0000000000000000 > > > > x1 : 0000000000000000 x0 : ffff3f460f3b29c0 Call trace: > > > > netif_get_rxqueue net/core/dev.c:4611 [inline] > > > > netif_receive_generic_xdp+0xb10/0xb50 net/core/dev.c:4683 > > > > do_xdp_generic net/core/dev.c:4777 [inline] > > > > do_xdp_generic+0x9c/0x190 net/core/dev.c:4770 > > > > tun_get_user+0xd94/0x2010 drivers/net/tun.c:1938 > > > > tun_chr_write_iter+0x98/0x100 drivers/net/tun.c:2036 > > > > call_write_iter > > > > include/linux/fs.h:1960 [inline] > > > > new_sync_write+0x260/0x370 fs/read_write.c:515 > > > > vfs_write+0x51c/0x61c > > > > fs/read_write.c:602 > > > > ksys_write+0xfc/0x200 fs/read_write.c:655 __do_sys_write > > > > fs/read_write.c:667 [inline] __se_sys_write fs/read_write.c:664 > > > > [inline] > > > > __arm64_sys_write+0x50/0x60 fs/read_write.c:664 __invoke_syscall > > > > arch/arm64/kernel/syscall.c:36 [inline] invoke_syscall > > > > arch/arm64/kernel/syscall.c:48 [inline] > > > > el0_svc_common.constprop.0+0xf4/0x414 > > > > arch/arm64/kernel/syscall.c:155 do_el0_svc+0x50/0x11c > > > > arch/arm64/kernel/syscall.c:217 > > > > el0_svc+0x20/0x30 arch/arm64/kernel/entry-common.c:353 > > > > el0_sync_handler+0xe4/0x1e0 arch/arm64/kernel/entry-common.c:369 > > > > el0_sync+0x148/0x180 arch/arm64/kernel/entry.S:683 > > > > > > > > This is because the detached queue is used to send data. Therefore, > > > > we need to check the queue status in the tun_chr_write_iter function. > > > > > > > > Fixes: cde8b15f1aab ("tuntap: add ioctl to attach or detach a file > > > > form tuntap device") > > > > Hello, > Sorry, fixes tag is wrong. The warning should be introduced by commit 3fe260e00cd0 (" net: tun: record RX queue in skb before do_xdp_generic() "). Before this, do_xdp_generic always uses queue0. Therefore, when the warning is generated due to detached, queue0 is used and is printed only once, which is harmless. So it's not a problem. > What do you think about this warning? I tend to keep this warning (it might be too late to fix). Thanks > > > > Not sure this deserves a stable. > > > > > > > Signed-off-by: Liu Jian <liujian56@...wei.com> > > > > --- > > > > v1->v2: add fixes tag > > > > drivers/net/tun.c | 5 +++++ > > > > 1 file changed, 5 insertions(+) > > > > > > > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c index > > > > 259b2b84b2b3..261411c1a6bb 100644 > > > > --- a/drivers/net/tun.c > > > > +++ b/drivers/net/tun.c > > > > @@ -2019,6 +2019,11 @@ static ssize_t tun_chr_write_iter(struct > > > > kiocb > > > *iocb, struct iov_iter *from) > > > > if (!tun) > > > > return -EBADFD; > > > > > > > > + if (tfile->detached) { > > > > > > tfile->detached is synchronized through rtnl_lock which is probably > > > not suitable for the datapath. We probably need to rcuify this. > > > > > > > + tun_put(tun); > > > > + return -ENETDOWN; > > > > > > Another question is that can some user space depend on this behaviour? > > > I wonder if it's more safe to pretend the packet was received here? > > > > > Thanks for your review. I don't know whether there was any depend on this > > behavior. > > If that's the case, I think it's better to keep this warning. > > What is your opinion on this warning? > > > > > Thanks > > > > > > > + } > > > > + > > > > if ((file->f_flags & O_NONBLOCK) || (iocb->ki_flags & IOCB_NOWAIT)) > > > > noblock = 1; > > > > > > > > -- > > > > 2.17.1 > > > > >
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