Using control_work instead of config_work as the 3rd argument to
container_of results in an invalid portdev pointer. Indeed, the work
structure is initialized as below:

    INIT_WORK(&portdev->config_work, &config_work_handler);

It leads to a crash when portdev->vdev is dereferenced later. This
bug
is triggered when the guest uses a virtio-console without multiport
feature and receives a config_changed virtio interrupt.
Signed-off-by: NG. Campana <gcampana@quarkslab.com>
Reviewed-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

struct ports_device includes a config field including the whole
virtio_console_config, but only max_nr_ports in there is ever updated or
used. The rest is unused and in fact does not even mirror the
device config. Drop everything except max_nr_ports,
saving some memory.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NJason Wang <jasowang@redhat.com>

Commit c6017e79 ("virtio: console: add locks around buffer removal
in port unplug path") added locking around the freeing of buffers in the
vq. However, when free_buf() is called with can_sleep = true and rproc
is enabled, it calls dma_free_coherent() directly, requiring interrupts
to be enabled. Currently a WARNING is triggered due to the spin locking
around free_buf, with a call stack like this:

WARNING: CPU: 3 PID: 121 at ./include/linux/dma-mapping.h:433
free_buf+0x1a8/0x288
Call Trace:
[<8040c538>] show_stack+0x74/0xc0
[<80757240>] dump_stack+0xd0/0x110
[<80430d98>] __warn+0xfc/0x130
[<80430ee0>] warn_slowpath_null+0x2c/0x3c
[<807e7c6c>] free_buf+0x1a8/0x288
[<807ea590>] remove_port_data+0x50/0xac
[<807ea6a0>] unplug_port+0xb4/0x1bc
[<807ea858>] virtcons_remove+0xb0/0xfc
[<807b6734>] virtio_dev_remove+0x58/0xc0
[<807f918c>] __device_release_driver+0xac/0x134
[<807f924c>] device_release_driver+0x38/0x50
[<807f7edc>] bus_remove_device+0xfc/0x130
[<807f4b74>] device_del+0x17c/0x21c
[<807f4c38>] device_unregister+0x24/0x38
[<807b6b50>] unregister_virtio_device+0x28/0x44

Fix this by restructuring the loops to allow the locks to only be taken
where it is necessary to protect the vqs, and release it while the
buffer is being freed.

Fixes: c6017e79 ("virtio: console: add locks around buffer removal in port unplug path")
Cc: stable@vger.kernel.org
Signed-off-by: NMatt Redfearn <matt.redfearn@imgtec.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

Kernel source files need not include <linux/kconfig.h> explicitly
because the top Makefile forces to include it with:

  -include $(srctree)/include/linux/kconfig.h

This commit removes explicit includes except the following:

  * arch/s390/include/asm/facilities_src.h
  * tools/testing/radix-tree/linux/kernel.h

These two are used for host programs.

Link: http://lkml.kernel.org/r/1473656164-11929-1-git-send-email-yamada.masahiro@socionext.comSigned-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NMiklos Szeredi <mszeredi@redhat.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

virtio_console uses a small DMA buffer for control requests.  Move
that buffer into heap memory.

Doing virtio DMA on the stack is normally okay on non-DMA-API virtio
systems (which is currently most of them), but it breaks completely
if the stack is virtually mapped.

Tested by typing both directions using picocom aimed at /dev/hvc0.
Signed-off-by: NAndy Lutomirski <luto@kernel.org>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NAmit Shah <amit.shah@redhat.com>

virtio_console uses a small DMA buffer for control requests.  Move
that buffer into heap memory.

Doing virtio DMA on the stack is normally okay on non-DMA-API virtio
systems (which is currently most of them), but it breaks completely
if the stack is virtually mapped (CONFIG_VMAP_STACK=y).

Tested by typing both directions using picocom aimed at /dev/hvc0.
Signed-off-by: NAndy Lutomirski <luto@kernel.org>
Reviewed-by: NAmit Shah <amit.shah@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: virtualization@lists.linux-foundation.org
Link: http://lkml.kernel.org/r/0afe68f9b4be6c95af9e7672b07acd0274c26dfe.1472569320.git.luto@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

My static checker complains that this sprintf() can overflow but really
it can't.  Just silence the warning by using snprintf().
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Use the normal return values for bool functions
Signed-off-by: NJoe Perches <joe@perches.com>
Reviewed-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

when multiport is off, virtio console invokes config access from irq
context, config access is blocking on s390.
Fix this up by scheduling work from config irq - similar to what we do
for multiport configs.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Cc: stable@kernel.org

when multiport is off, we don't initialize config work,
but we then cancel uninitialized control_work on freeze.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Cc: stable@kernel.org

Strictly, it's only needed when we have features (size or multiport).
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

Some devices might not implement config space access
(e.g. remoteproc used not to - before 3.9).
virtio/console needs config space access so make it
fail gracefully if not there.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Some devices might not implement config space access
(e.g. remoteproc used not to - before 3.9).
virtio/console needs config space access so make it
fail gracefully if not there.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

CHECK drivers/char/virtio_console.c
drivers/char/virtio_console.c:687:36: warning: incorrect type in
	argument 1 (different address spaces)
drivers/char/virtio_console.c:687:36:    expected void [noderef]
	<asn:1>*to
drivers/char/virtio_console.c:687:36:    got char *out_buf
drivers/char/virtio_console.c:790:35: warning: incorrect type in
	argument 2 (different address spaces)
drivers/char/virtio_console.c:790:35:    expected char *out_buf
drivers/char/virtio_console.c:790:35:    got char [noderef]
	<asn:1>*ubuf

fill_readbuf is reused with both kernel and userspace pointers,
depending on value of to_user flag.

Tag address parameter as __user, and cast to/from regular pointer type
when we know it's safe.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

Core activates this bit automatically now,
drop it from drivers that set it explicitly.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

Pretty straight-forward, just use accessors for all fields.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

It seemed like a good idea to use bitmap for features
in struct virtio_device, but it's actually a pain,
and seems to become even more painful when we get more
than 32 feature bits.  Just change it to a u32 for now.

Based on patch by Rusty.
Suggested-by: NDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NCornelia Huck <cornelia.huck@de.ibm.com>

Commit f5866db6 (virtio_console: enable VQs early) tried to make
sure that DRIVER_OK was set when virtio_console started using its
virtqueues. Doing this in add_port(), however, means that we try
to set DRIVER_OK again when when a port is dynamically added after
the probe function is done.

Let's move virtio_device_ready() to the probe function just before
trying to use the virtqueues instead. This is fine as nothing can
fail inbetween.
Reported-by: NThomas Graf <tgraf@suug.ch>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

virtio spec requires drivers to set DRIVER_OK before using VQs.
This is set automatically after resume returns, virtio console violated this
rule by adding inbufs, which causes the VQ to be used directly within
restore.

To fix, call virtio_device_ready before using VQs.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

virtio spec requires drivers to set DRIVER_OK before using VQs.
This is set automatically after probe returns, virtio console violated this
rule by adding inbufs, which causes the VQ to be used directly within
probe.

To fix, call virtio_device_ready before using VQs.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

Fix checkpatch warning:
WARNING: debugfs_remove_recursive(NULL) is safe this check is probably not required

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: virtualization@lists.linux-foundation.org
Reviewed-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NFabian Frederick <fabf@skynet.be>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

all pipe_buffer_operations have the same instances of those...
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

While we are at it, don't do kmap() under kmap_atomic(), *especially*
for a page we'd allocated with GFP_KERNEL.  It's spelled "page_address",
and had that been more than that, we'd have a real trouble - kmap_high()
can block, and doing that while holding kmap_atomic() is a Bad Idea(tm).
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

If virtqueue_get_buf() returns with a NULL pointer it should be verified
if the virtqueue is broken, in order to avoid loop calling cpu_relax().
Signed-off-by: NHeinz Graalfs <graalfs@linux.vnet.ibm.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

This lets the transport do endian conversion if necessary, and insulates
the drivers from the difference.

Most drivers can use the simple helpers virtio_cread() and virtio_cwrite().
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

The freeze and restore functions defined in virtio drivers are used
for suspend and hibernate, so CONFIG_PM_SLEEP is more appropriate than
CONFIG_PM. This patch replace all CONFIG_PM with CONFIG_PM_SLEEP for
virtio drivers that implement freeze and restore callbacks.
Signed-off-by: NAaron Lu <aaron.lu@intel.com>
Reviewed-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

Remove the debugfs path before freeing port->name, to prevent a possible
use-after-free.
Reported-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

The PTR_ERR(NULL) here is not useful.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

send_sigio_to_port() checks the value of guest_connected, which we
always modify under the inbuf_lock; make sure invocations of
send_sigio_to_port() have take the inbuf_lock around the call.
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

Port unplug can race with close() in port_fops_release().
port_fops_release() already takes the necessary locks, ensure
unplug_port() does that too.
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

The removal functions act on the vqs, and the vq operations need to be
locked.
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

If a port gets unplugged while a user is blocked on read(), -ENODEV is
returned.  However, subsequent read()s returned 0, indicating there's no
host-side connection (but not indicating the device went away).

This also happened when a port was unplugged and the user didn't have
any blocking operation pending.  If the user didn't monitor the SIGIO
signal, they won't have a chance to find out if the port went away.

Fix by returning -ENODEV on all read()s after the port gets unplugged.
write() already behaves this way.

CC: <stable@vger.kernel.org>
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

SIGIO should be sent when a port gets unplugged.  It should only be sent
to prcesses that have the port opened, and have asked for SIGIO to be
delivered.  We were clearing out guest_connected before calling
send_sigio_to_port(), resulting in a sigio not getting sent to
processes.

Fix by setting guest_connected to false after invoking the sigio
function.

CC: <stable@vger.kernel.org>
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

We used to keep the port's char device structs and the /sys entries
around till the last reference to the port was dropped.  This is
actually unnecessary, and resulted in buggy behaviour:

1. Open port in guest
2. Hot-unplug port
3. Hot-plug a port with the same 'name' property as the unplugged one

This resulted in hot-plug being unsuccessful, as a port with the same
name already exists (even though it was unplugged).

This behaviour resulted in a warning message like this one:

-------------------8<---------------------------------------
WARNING: at fs/sysfs/dir.c:512 sysfs_add_one+0xc9/0x130() (Not tainted)
Hardware name: KVM
sysfs: cannot create duplicate filename
'/devices/pci0000:00/0000:00:04.0/virtio0/virtio-ports/vport0p1'

Call Trace:
 [<ffffffff8106b607>] ? warn_slowpath_common+0x87/0xc0
 [<ffffffff8106b6f6>] ? warn_slowpath_fmt+0x46/0x50
 [<ffffffff811f2319>] ? sysfs_add_one+0xc9/0x130
 [<ffffffff811f23e8>] ? create_dir+0x68/0xb0
 [<ffffffff811f2469>] ? sysfs_create_dir+0x39/0x50
 [<ffffffff81273129>] ? kobject_add_internal+0xb9/0x260
 [<ffffffff812733d8>] ? kobject_add_varg+0x38/0x60
 [<ffffffff812734b4>] ? kobject_add+0x44/0x70
 [<ffffffff81349de4>] ? get_device_parent+0xf4/0x1d0
 [<ffffffff8134b389>] ? device_add+0xc9/0x650

-------------------8<---------------------------------------

Instead of relying on guest applications to release all references to
the ports, we should go ahead and unregister the port from all the core
layers.  Any open/read calls on the port will then just return errors,
and an unplug/plug operation on the host will succeed as expected.

This also caused buggy behaviour in case of the device removal (not just
a port): when the device was removed (which means all ports on that
device are removed automatically as well), the ports with active
users would clean up only when the last references were dropped -- and
it would be too late then to be referencing char device pointers,
resulting in oopses:

-------------------8<---------------------------------------
PID: 6162   TASK: ffff8801147ad500  CPU: 0   COMMAND: "cat"
 #0 [ffff88011b9d5a90] machine_kexec at ffffffff8103232b
 #1 [ffff88011b9d5af0] crash_kexec at ffffffff810b9322
 #2 [ffff88011b9d5bc0] oops_end at ffffffff814f4a50
 #3 [ffff88011b9d5bf0] die at ffffffff8100f26b
 #4 [ffff88011b9d5c20] do_general_protection at ffffffff814f45e2
 #5 [ffff88011b9d5c50] general_protection at ffffffff814f3db5
    [exception RIP: strlen+2]
    RIP: ffffffff81272ae2  RSP: ffff88011b9d5d00  RFLAGS: 00010246
    RAX: 0000000000000000  RBX: ffff880118901c18  RCX: 0000000000000000
    RDX: ffff88011799982c  RSI: 00000000000000d0  RDI: 3a303030302f3030
    RBP: ffff88011b9d5d38   R8: 0000000000000006   R9: ffffffffa0134500
    R10: 0000000000001000  R11: 0000000000001000  R12: ffff880117a1cc10
    R13: 00000000000000d0  R14: 0000000000000017  R15: ffffffff81aff700
    ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
 #6 [ffff88011b9d5d00] kobject_get_path at ffffffff8126dc5d
 #7 [ffff88011b9d5d40] kobject_uevent_env at ffffffff8126e551
 #8 [ffff88011b9d5dd0] kobject_uevent at ffffffff8126e9eb
 #9 [ffff88011b9d5de0] device_del at ffffffff813440c7

-------------------8<---------------------------------------

So clean up when we have all the context, and all that's left to do when
the references to the port have dropped is to free up the port struct
itself.

CC: <stable@vger.kernel.org>
Reported-by: Nchayang <chayang@redhat.com>
Reported-by: NYOGANANTH SUBRAMANIAN <anantyog@in.ibm.com>
Reported-by: NFuXiangChun <xfu@redhat.com>
Reported-by: NQunfang Zhang <qzhang@redhat.com>
Reported-by: NSibiao Luo <sluo@redhat.com>
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

Between open() being called and processed, the port can be unplugged.
Check if this happened, and bail out.

A simple test script to reproduce this is:

while true; do for i in $(seq 1 100); do echo $i > /dev/vport0p3; done; done;

This opens and closes the port a lot of times; unplugging the port while
this is happening triggers the bug.

CC: <stable@vger.kernel.org>
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

There's a window between find_port_by_devt() returning a port and us
taking a kref on the port, where the port could get unplugged.  Fix it
by taking the reference in find_port_by_devt() itself.

Problem reported and analyzed by Mateusz Guzik.

CC: <stable@vger.kernel.org>
Reported-by: NMateusz Guzik <mguzik@redhat.com>
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

Add pipe_lock/unlock for splice_write to avoid oops by following competition:

(1) An application gets fds of a trace buffer, virtio-serial, pipe.
(2) The application does fork()
(3) The processes execute splice_read(trace buffer) and
    splice_write(virtio-serial) via same pipe.

        <parent>                   <child>
  get fds of a trace buffer,
         virtio-serial, pipe
          |
        fork()----------create--------+
          |                           |
      splice(read)                    |           ---+
      splice(write)                   |              +-- no competition
          |                       splice(read)       |
          |                       splice(write)   ---+
          |                           |
      splice(read)                    |
      splice(write)               splice(read)    ------ competition
          |                       splice(write)

Two processes share a pipe_inode_info structure. If the child execute
splice(read) when the parent tries to execute splice(write), the
structure can be broken. Existing virtio-serial driver does not get
lock for the structure in splice_write, so this competition will induce
oops.

<oops messages>
 BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
 IP: [<ffffffff811a6b5f>] splice_from_pipe_feed+0x6f/0x130
 PGD 7223e067 PUD 72391067 PMD 0
 Oops: 0000 [#1] SMP
 Modules linked in: lockd bnep bluetooth rfkill sunrpc ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables snd_hda_intel snd_hda_codec snd_hwdep snd_pcm snd_page_alloc snd_timer snd soundcore pcspkr virtio_net virtio_balloon i2c_piix4 i2c_core microcode uinput floppy
 CPU: 0 PID: 1072 Comm: compete-test Not tainted 3.10.0ws+ #55
 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
 task: ffff880071b98000 ti: ffff88007b55e000 task.ti: ffff88007b55e000
 RIP: 0010:[<ffffffff811a6b5f>]  [<ffffffff811a6b5f>] splice_from_pipe_feed+0x6f/0x130
 RSP: 0018:ffff88007b55fd78  EFLAGS: 00010287
 RAX: 0000000000000000 RBX: ffff88007b55fe20 RCX: 0000000000000000
 RDX: 0000000000001000 RSI: ffff88007a95ba30 RDI: ffff880036f9e6c0
 RBP: ffff88007b55fda8 R08: 00000000000006ec R09: ffff880077626708
 R10: 0000000000000003 R11: ffffffff8139ca59 R12: ffff88007a95ba30
 R13: 0000000000000000 R14: ffffffff8139dd00 R15: ffff880036f9e6c0
 FS:  00007f2e2e3a0740(0000) GS:ffff88007fc00000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
 CR2: 0000000000000018 CR3: 0000000071bd1000 CR4: 00000000000006f0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
 Stack:
  ffffffff8139ca59 ffff88007b55fe20 ffff880036f9e6c0 ffffffff8139dd00
  ffff8800776266c0 ffff880077626708 ffff88007b55fde8 ffffffff811a6e8e
  ffff88007b55fde8 ffffffff8139ca59 ffff880036f9e6c0 ffff88007b55fe20
 Call Trace:
  [<ffffffff8139ca59>] ? alloc_buf.isra.13+0x39/0xb0
  [<ffffffff8139dd00>] ? virtcons_restore+0x100/0x100
  [<ffffffff811a6e8e>] __splice_from_pipe+0x7e/0x90
  [<ffffffff8139ca59>] ? alloc_buf.isra.13+0x39/0xb0
  [<ffffffff8139d739>] port_fops_splice_write+0xe9/0x140
  [<ffffffff8127a3f4>] ? selinux_file_permission+0xc4/0x120
  [<ffffffff8139d650>] ? wait_port_writable+0x1b0/0x1b0
  [<ffffffff811a6fe0>] do_splice_from+0xa0/0x110
  [<ffffffff811a951f>] SyS_splice+0x5ff/0x6b0
  [<ffffffff8161facf>] tracesys+0xdd/0xe2
 Code: 49 8b 87 80 00 00 00 4c 8d 24 d0 8b 53 04 41 8b 44 24 0c 4d 8b 6c 24 10 39 d0 89 03 76 02 89 13 49 8b 44 24 10 4c 89 e6 4c 89 ff <ff> 50 18 85 c0 0f 85 aa 00 00 00 48 89 da 4c 89 e6 4c 89 ff 41
 RIP  [<ffffffff811a6b5f>] splice_from_pipe_feed+0x6f/0x130
  RSP <ffff88007b55fd78>
 CR2: 0000000000000018
 ---[ end trace 24572beb7764de59 ]---

V2: Fix a locking problem for error
V3: Add Reviewed-by lines and stable@ line in sign-off area
Signed-off-by: NYoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Reviewed-by: NAmit Shah <amit.shah@redhat.com>
Reviewed-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Amit Shah <amit.shah@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable@vger.kernel.org
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

Quit from splice_write if pipe->nrbufs is 0 for avoiding oops in virtio-serial.

When an application was doing splice from a kernel buffer to virtio-serial on
a guest, the application received signal(SIGINT). This situation will normally
happen, but the kernel executed a kernel panic by oops as follows:

 BUG: unable to handle kernel paging request at ffff882071c8ef28
 IP: [<ffffffff812de48f>] sg_init_table+0x2f/0x50
 PGD 1fac067 PUD 0
 Oops: 0000 [#1] SMP
 Modules linked in: lockd sunrpc bnep bluetooth rfkill ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables snd_hda_intel snd_hda_codec snd_hwdep snd_pcm snd_page_alloc snd_timer snd microcode virtio_balloon virtio_net pcspkr soundcore i2c_piix4 i2c_core uinput floppy
 CPU: 1 PID: 908 Comm: trace-cmd Not tainted 3.10.0+ #49
 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
 task: ffff880071c64650 ti: ffff88007bf24000 task.ti: ffff88007bf24000
 RIP: 0010:[<ffffffff812de48f>]  [<ffffffff812de48f>] sg_init_table+0x2f/0x50
 RSP: 0018:ffff88007bf25dd8  EFLAGS: 00010286
 RAX: 0000001fffffffe0 RBX: ffff882071c8ef28 RCX: 0000000000000000
 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff880071c8ef48
 RBP: ffff88007bf25de8 R08: ffff88007fd15d40 R09: ffff880071c8ef48
 R10: ffffea0001c71040 R11: ffffffff8139c555 R12: 0000000000000000
 R13: ffff88007506a3c0 R14: ffff88007c862500 R15: ffff880071c8ef00
 FS:  00007f0a3646c740(0000) GS:ffff88007fd00000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: ffff882071c8ef28 CR3: 000000007acbb000 CR4: 00000000000006e0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
 Stack:
  ffff880071c8ef48 ffff88007bf25e20 ffff88007bf25e88 ffffffff8139d6fa
  ffff88007bf25e28 ffffffff8127a3f4 0000000000000000 0000000000000000
  ffff880071c8ef48 0000100000000000 0000000000000003 ffff88007bf25e08
 Call Trace:
  [<ffffffff8139d6fa>] port_fops_splice_write+0xaa/0x130
  [<ffffffff8127a3f4>] ? selinux_file_permission+0xc4/0x120
  [<ffffffff8139d650>] ? wait_port_writable+0x1b0/0x1b0
  [<ffffffff811a6fe0>] do_splice_from+0xa0/0x110
  [<ffffffff811a951f>] SyS_splice+0x5ff/0x6b0
  [<ffffffff8161f8c2>] system_call_fastpath+0x16/0x1b
 Code: c1 e2 05 48 89 e5 48 83 ec 10 4c 89 65 f8 41 89 f4 31 f6 48 89 5d f0 48 89 fb e8 8d ce ff ff 41 8d 44 24 ff 48 c1 e0 05 48 01 c3 <48> 8b 03 48 83 e0 fe 48 83 c8 02 48 89 03 48 8b 5d f0 4c 8b 65
 RIP  [<ffffffff812de48f>] sg_init_table+0x2f/0x50
  RSP <ffff88007bf25dd8>
 CR2: ffff882071c8ef28
 ---[ end trace 86323505eb42ea8f ]---

It seems to induce pagefault in sg_init_tabel() when pipe->nrbufs is equal to
zero. This may happen in a following situation:

(1) The application normally does splice(read) from a kernel buffer, then does
    splice(write) to virtio-serial.
(2) The application receives SIGINT when is doing splice(read), so splice(read)
    is failed by EINTR. However, the application does not finish the operation.
(3) The application tries to do splice(write) without pipe->nrbufs.
(4) The virtio-console driver tries to touch scatterlist structure sgl in
    sg_init_table(), but the region is out of bound.

To avoid the case, a kernel should check whether pipe->nrbufs is empty or not
when splice_write is executed in the virtio-console driver.

V3: Add Reviewed-by lines and stable@ line in sign-off area.
Signed-off-by: NYoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Reviewed-by: NAmit Shah <amit.shah@redhat.com>
Reviewed-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Amit Shah <amit.shah@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable@vger.kernel.org
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

Returning EMFILE (process has too many open files) is incorrect to
indicate a port is already open by another process.  Use EBUSY for that.

This does change what we report to userspace, but I believe userspace
can look at it this way: it gets EBUSY, a new error code, instead of
EMFILE.  It's still an error, and that's not changing.
Reported-by: NMateusz Guzik <mguzik@redhat.com>
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>