[PATCH] vhost_net: initialize rx_ring in vhost_net_open()

[PATCH] vhost_net: initialize rx_ring in vhost_net_open()

[Alexander Potapenko]

KMSAN reported a use of uninit memory in vhost_net_buf_unproduce()
while trying to access n->vqs[VHOST_NET_VQ_TX].rx_ring:

==================================================================
BUG: KMSAN: use of uninitialized memory in vhost_net_buf_unproduce+0x7bb/0x9a0 drivers/vho
et.c:170
CPU: 0 PID: 3021 Comm: syz-fuzzer Not tainted 4.16.0-rc4+ #3853
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x185/0x1d0 lib/dump_stack.c:53
 kmsan_report+0x142/0x1f0 mm/kmsan/kmsan.c:1093
 __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
 vhost_net_buf_unproduce+0x7bb/0x9a0 drivers/vhost/net.c:170
 vhost_net_stop_vq drivers/vhost/net.c:974 [inline]
 vhost_net_stop+0x146/0x380 drivers/vhost/net.c:982
 vhost_net_release+0xb1/0x4f0 drivers/vhost/net.c:1015
 __fput+0x49f/0xa00 fs/file_table.c:209
 ____fput+0x37/0x40 fs/file_table.c:243
 task_work_run+0x243/0x2c0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 exit_to_usermode_loop arch/x86/entry/common.c:166 [inline]
 prepare_exit_to_usermode+0x349/0x3b0 arch/x86/entry/common.c:196
 syscall_return_slowpath+0xf3/0x6d0 arch/x86/entry/common.c:265
 do_syscall_64+0x34d/0x450 arch/x86/entry/common.c:292
...
origin:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:303 [inline]
 kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:213
 kmsan_kmalloc_large+0x6f/0xd0 mm/kmsan/kmsan.c:392
 kmalloc_large_node_hook mm/slub.c:1366 [inline]
 kmalloc_large_node mm/slub.c:3808 [inline]
 __kmalloc_node+0x100e/0x1290 mm/slub.c:3818
 kmalloc_node include/linux/slab.h:554 [inline]
 kvmalloc_node+0x1a5/0x2e0 mm/util.c:419
 kvmalloc include/linux/mm.h:541 [inline]
 vhost_net_open+0x64/0x5f0 drivers/vhost/net.c:921
 misc_open+0x7b5/0x8b0 drivers/char/misc.c:154
 chrdev_open+0xc28/0xd90 fs/char_dev.c:417
 do_dentry_open+0xccb/0x1430 fs/open.c:752
 vfs_open+0x272/0x2e0 fs/open.c:866
 do_last fs/namei.c:3378 [inline]
 path_openat+0x49ad/0x6580 fs/namei.c:3519
 do_filp_open+0x267/0x640 fs/namei.c:3553
 do_sys_open+0x6ad/0x9c0 fs/open.c:1059
 SYSC_openat+0xc7/0xe0 fs/open.c:1086
 SyS_openat+0x63/0x90 fs/open.c:1080
 do_syscall_64+0x2f1/0x450 arch/x86/entry/common.c:287
==================================================================

Signed-off-by: Alexander Potapenko <glider@google.com>
---
 drivers/vhost/net.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 610cba276d47..60f1080bffc7 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -948,6 +948,7 @@ static int vhost_net_open(struct inode *inode, struct file *f)
 		n->vqs[i].done_idx = 0;
 		n->vqs[i].vhost_hlen = 0;
 		n->vqs[i].sock_hlen = 0;
+		n->vqs[i].rx_ring = NULL;
 		vhost_net_buf_init(&n->vqs[i].rxq);
 	}
 	vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX);
-- 
2.16.2.395.g2e18187dfd-goog

Re: [PATCH] vhost_net: initialize rx_ring in vhost_net_open()

[Eric Dumazet]

On 03/08/2018 05:37 AM, Alexander Potapenko wrote:
> KMSAN reported a use of uninit memory in vhost_net_buf_unproduce()
> while trying to access n->vqs[VHOST_NET_VQ_TX].rx_ring:
> 
> 
> ==================================================================
> 
> Signed-off-by: Alexander Potapenko <glider@google.com>

Please identify bug origin with a Fixes: tag

This will tremendously help stable teams that are struggling with many 
backports these days.

Thanks.

> ---
>   drivers/vhost/net.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 610cba276d47..60f1080bffc7 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -948,6 +948,7 @@ static int vhost_net_open(struct inode *inode, struct file *f)
>   		n->vqs[i].done_idx = 0;
>   		n->vqs[i].vhost_hlen = 0;
>   		n->vqs[i].sock_hlen = 0;
> +		n->vqs[i].rx_ring = NULL;
>   		vhost_net_buf_init(&n->vqs[i].rxq);
>   	}
>   	vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX);
> 

Re: [PATCH] vhost_net: initialize rx_ring in vhost_net_open()

[Alexander Potapenko]

On Thu, Mar 8, 2018 at 4:15 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
>
> On 03/08/2018 05:37 AM, Alexander Potapenko wrote:
>>
>> KMSAN reported a use of uninit memory in vhost_net_buf_unproduce()
>> while trying to access n->vqs[VHOST_NET_VQ_TX].rx_ring:
>>
>>
>> ==================================================================
>>
>> Signed-off-by: Alexander Potapenko <glider@google.com>
>
>
> Please identify bug origin with a Fixes: tag
Fixes: 5990a30510ed1 ("tun/tap: use ptr_ring instead of skb_array")

The above patch introduced rx_ring, but the problem existed before.

> This will tremendously help stable teams that are struggling with many
> backports these days.
>
> Thanks.
>
>
>> ---
>>   drivers/vhost/net.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
>> index 610cba276d47..60f1080bffc7 100644
>> --- a/drivers/vhost/net.c
>> +++ b/drivers/vhost/net.c
>> @@ -948,6 +948,7 @@ static int vhost_net_open(struct inode *inode, struct
>> file *f)
>>                 n->vqs[i].done_idx = 0;
>>                 n->vqs[i].vhost_hlen = 0;
>>                 n->vqs[i].sock_hlen = 0;
>> +               n->vqs[i].rx_ring = NULL;
>>                 vhost_net_buf_init(&n->vqs[i].rxq);
>>         }
>>         vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX);
>>
>



-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg

Re: [PATCH] vhost_net: initialize rx_ring in vhost_net_open()

[Michael S. Tsirkin]

On Thu, Mar 08, 2018 at 02:37:17PM +0100, Alexander Potapenko wrote:
> KMSAN reported a use of uninit memory in vhost_net_buf_unproduce()
> while trying to access n->vqs[VHOST_NET_VQ_TX].rx_ring:
> 
> ==================================================================
> BUG: KMSAN: use of uninitialized memory in vhost_net_buf_unproduce+0x7bb/0x9a0 drivers/vho
> et.c:170
> CPU: 0 PID: 3021 Comm: syz-fuzzer Not tainted 4.16.0-rc4+ #3853
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
> Call Trace:
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x185/0x1d0 lib/dump_stack.c:53
>  kmsan_report+0x142/0x1f0 mm/kmsan/kmsan.c:1093
>  __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
>  vhost_net_buf_unproduce+0x7bb/0x9a0 drivers/vhost/net.c:170
>  vhost_net_stop_vq drivers/vhost/net.c:974 [inline]
>  vhost_net_stop+0x146/0x380 drivers/vhost/net.c:982
>  vhost_net_release+0xb1/0x4f0 drivers/vhost/net.c:1015
>  __fput+0x49f/0xa00 fs/file_table.c:209
>  ____fput+0x37/0x40 fs/file_table.c:243
>  task_work_run+0x243/0x2c0 kernel/task_work.c:113
>  tracehook_notify_resume include/linux/tracehook.h:191 [inline]
>  exit_to_usermode_loop arch/x86/entry/common.c:166 [inline]
>  prepare_exit_to_usermode+0x349/0x3b0 arch/x86/entry/common.c:196
>  syscall_return_slowpath+0xf3/0x6d0 arch/x86/entry/common.c:265
>  do_syscall_64+0x34d/0x450 arch/x86/entry/common.c:292
> ...
> origin:
>  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:303 [inline]
>  kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:213
>  kmsan_kmalloc_large+0x6f/0xd0 mm/kmsan/kmsan.c:392
>  kmalloc_large_node_hook mm/slub.c:1366 [inline]
>  kmalloc_large_node mm/slub.c:3808 [inline]
>  __kmalloc_node+0x100e/0x1290 mm/slub.c:3818
>  kmalloc_node include/linux/slab.h:554 [inline]
>  kvmalloc_node+0x1a5/0x2e0 mm/util.c:419
>  kvmalloc include/linux/mm.h:541 [inline]
>  vhost_net_open+0x64/0x5f0 drivers/vhost/net.c:921
>  misc_open+0x7b5/0x8b0 drivers/char/misc.c:154
>  chrdev_open+0xc28/0xd90 fs/char_dev.c:417
>  do_dentry_open+0xccb/0x1430 fs/open.c:752
>  vfs_open+0x272/0x2e0 fs/open.c:866
>  do_last fs/namei.c:3378 [inline]
>  path_openat+0x49ad/0x6580 fs/namei.c:3519
>  do_filp_open+0x267/0x640 fs/namei.c:3553
>  do_sys_open+0x6ad/0x9c0 fs/open.c:1059
>  SYSC_openat+0xc7/0xe0 fs/open.c:1086
>  SyS_openat+0x63/0x90 fs/open.c:1080
>  do_syscall_64+0x2f1/0x450 arch/x86/entry/common.c:287
> ==================================================================
> 
> Signed-off-by: Alexander Potapenko <glider@google.com>
> ---
>  drivers/vhost/net.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 610cba276d47..60f1080bffc7 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -948,6 +948,7 @@ static int vhost_net_open(struct inode *inode, struct file *f)
>  		n->vqs[i].done_idx = 0;
>  		n->vqs[i].vhost_hlen = 0;
>  		n->vqs[i].sock_hlen = 0;
> +		n->vqs[i].rx_ring = NULL;
>  		vhost_net_buf_init(&n->vqs[i].rxq);
>  	}
>  	vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX);
> -- 
> 2.16.2.395.g2e18187dfd-goog


I suspect that's not sufficient. rx ring is tied to the tap device.
I think we need to drop it every time we drop the device.

Re: [PATCH] vhost_net: initialize rx_ring in vhost_net_open()

[Eric Dumazet]

On 03/08/2018 07:20 AM, Alexander Potapenko wrote:
> On Thu, Mar 8, 2018 at 4:15 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
>>
>>
>> On 03/08/2018 05:37 AM, Alexander Potapenko wrote:
>>>
>>> KMSAN reported a use of uninit memory in vhost_net_buf_unproduce()
>>> while trying to access n->vqs[VHOST_NET_VQ_TX].rx_ring:
>>>
>>>
>>> ==================================================================
>>>
>>> Signed-off-by: Alexander Potapenko <glider@google.com>
>>
>>
>> Please identify bug origin with a Fixes: tag
> Fixes: 5990a30510ed1 ("tun/tap: use ptr_ring instead of skb_array")

Please send a V2 with this added tag. patchwork does not recognize it yet.

David Miller has also a lot on his plate, please everybody be gentle 
with both stable teams and maintainers.

Thanks.


> 
> The above patch introduced rx_ring, but the problem existed before.
> 
>> This will tremendously help stable teams that are struggling with many
>> backports these days.
>>
>> Thanks.
>>
>>
>>> ---
>>>    drivers/vhost/net.c | 1 +
>>>    1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
>>> index 610cba276d47..60f1080bffc7 100644
>>> --- a/drivers/vhost/net.c
>>> +++ b/drivers/vhost/net.c
>>> @@ -948,6 +948,7 @@ static int vhost_net_open(struct inode *inode, struct
>>> file *f)
>>>                  n->vqs[i].done_idx = 0;
>>>                  n->vqs[i].vhost_hlen = 0;
>>>                  n->vqs[i].sock_hlen = 0;
>>> +               n->vqs[i].rx_ring = NULL;
>>>                  vhost_net_buf_init(&n->vqs[i].rxq);
>>>          }
>>>          vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX);
>>>
>>
> 
> 
> 

Re: [PATCH] vhost_net: initialize rx_ring in vhost_net_open()

[Alexander Potapenko]

On Thu, Mar 8, 2018 at 4:45 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
>
> On 03/08/2018 07:20 AM, Alexander Potapenko wrote:
>>
>> On Thu, Mar 8, 2018 at 4:15 PM, Eric Dumazet <eric.dumazet@gmail.com>
>> wrote:
>>>
>>>
>>>
>>> On 03/08/2018 05:37 AM, Alexander Potapenko wrote:
>>>>
>>>>
>>>> KMSAN reported a use of uninit memory in vhost_net_buf_unproduce()
>>>> while trying to access n->vqs[VHOST_NET_VQ_TX].rx_ring:
>>>>
>>>>
>>>> ==================================================================
>>>>
>>>> Signed-off-by: Alexander Potapenko <glider@google.com>
>>>
>>>
>>>
>>> Please identify bug origin with a Fixes: tag
>>
>> Fixes: 5990a30510ed1 ("tun/tap: use ptr_ring instead of skb_array")
>
>
> Please send a V2 with this added tag. patchwork does not recognize it yet.
Ok, will do. Thanks for reminding about the tag!
> David Miller has also a lot on his plate, please everybody be gentle with
> both stable teams and maintainers.
>
> Thanks.
>
>
>
>>
>> The above patch introduced rx_ring, but the problem existed before.
>>
>>> This will tremendously help stable teams that are struggling with many
>>> backports these days.
>>>
>>> Thanks.
>>>
>>>
>>>> ---
>>>>    drivers/vhost/net.c | 1 +
>>>>    1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
>>>> index 610cba276d47..60f1080bffc7 100644
>>>> --- a/drivers/vhost/net.c
>>>> +++ b/drivers/vhost/net.c
>>>> @@ -948,6 +948,7 @@ static int vhost_net_open(struct inode *inode,
>>>> struct
>>>> file *f)
>>>>                  n->vqs[i].done_idx = 0;
>>>>                  n->vqs[i].vhost_hlen = 0;
>>>>                  n->vqs[i].sock_hlen = 0;
>>>> +               n->vqs[i].rx_ring = NULL;
>>>>                  vhost_net_buf_init(&n->vqs[i].rxq);
>>>>          }
>>>>          vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX);
>>>>
>>>
>>
>>
>>
>



-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg

Re: [PATCH] vhost_net: initialize rx_ring in vhost_net_open()

[Alexander Potapenko]

On Thu, Mar 8, 2018 at 4:33 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> On Thu, Mar 08, 2018 at 02:37:17PM +0100, Alexander Potapenko wrote:
>> KMSAN reported a use of uninit memory in vhost_net_buf_unproduce()
>> while trying to access n->vqs[VHOST_NET_VQ_TX].rx_ring:
>>
>> ==================================================================
>> BUG: KMSAN: use of uninitialized memory in vhost_net_buf_unproduce+0x7bb/0x9a0 drivers/vho
>> et.c:170
>> CPU: 0 PID: 3021 Comm: syz-fuzzer Not tainted 4.16.0-rc4+ #3853
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
>> Call Trace:
>>  __dump_stack lib/dump_stack.c:17 [inline]
>>  dump_stack+0x185/0x1d0 lib/dump_stack.c:53
>>  kmsan_report+0x142/0x1f0 mm/kmsan/kmsan.c:1093
>>  __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
>>  vhost_net_buf_unproduce+0x7bb/0x9a0 drivers/vhost/net.c:170
>>  vhost_net_stop_vq drivers/vhost/net.c:974 [inline]
>>  vhost_net_stop+0x146/0x380 drivers/vhost/net.c:982
>>  vhost_net_release+0xb1/0x4f0 drivers/vhost/net.c:1015
>>  __fput+0x49f/0xa00 fs/file_table.c:209
>>  ____fput+0x37/0x40 fs/file_table.c:243
>>  task_work_run+0x243/0x2c0 kernel/task_work.c:113
>>  tracehook_notify_resume include/linux/tracehook.h:191 [inline]
>>  exit_to_usermode_loop arch/x86/entry/common.c:166 [inline]
>>  prepare_exit_to_usermode+0x349/0x3b0 arch/x86/entry/common.c:196
>>  syscall_return_slowpath+0xf3/0x6d0 arch/x86/entry/common.c:265
>>  do_syscall_64+0x34d/0x450 arch/x86/entry/common.c:292
>> ...
>> origin:
>>  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:303 [inline]
>>  kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:213
>>  kmsan_kmalloc_large+0x6f/0xd0 mm/kmsan/kmsan.c:392
>>  kmalloc_large_node_hook mm/slub.c:1366 [inline]
>>  kmalloc_large_node mm/slub.c:3808 [inline]
>>  __kmalloc_node+0x100e/0x1290 mm/slub.c:3818
>>  kmalloc_node include/linux/slab.h:554 [inline]
>>  kvmalloc_node+0x1a5/0x2e0 mm/util.c:419
>>  kvmalloc include/linux/mm.h:541 [inline]
>>  vhost_net_open+0x64/0x5f0 drivers/vhost/net.c:921
>>  misc_open+0x7b5/0x8b0 drivers/char/misc.c:154
>>  chrdev_open+0xc28/0xd90 fs/char_dev.c:417
>>  do_dentry_open+0xccb/0x1430 fs/open.c:752
>>  vfs_open+0x272/0x2e0 fs/open.c:866
>>  do_last fs/namei.c:3378 [inline]
>>  path_openat+0x49ad/0x6580 fs/namei.c:3519
>>  do_filp_open+0x267/0x640 fs/namei.c:3553
>>  do_sys_open+0x6ad/0x9c0 fs/open.c:1059
>>  SYSC_openat+0xc7/0xe0 fs/open.c:1086
>>  SyS_openat+0x63/0x90 fs/open.c:1080
>>  do_syscall_64+0x2f1/0x450 arch/x86/entry/common.c:287
>> ==================================================================
>>
>> Signed-off-by: Alexander Potapenko <glider@google.com>
>> ---
>>  drivers/vhost/net.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
>> index 610cba276d47..60f1080bffc7 100644
>> --- a/drivers/vhost/net.c
>> +++ b/drivers/vhost/net.c
>> @@ -948,6 +948,7 @@ static int vhost_net_open(struct inode *inode, struct file *f)
>>               n->vqs[i].done_idx = 0;
>>               n->vqs[i].vhost_hlen = 0;
>>               n->vqs[i].sock_hlen = 0;
>> +             n->vqs[i].rx_ring = NULL;
>>               vhost_net_buf_init(&n->vqs[i].rxq);
>>       }
>>       vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX);
>> --
>> 2.16.2.395.g2e18187dfd-goog
>
>
> I suspect that's not sufficient. rx ring is tied to the tap device.
> I think we need to drop it every time we drop the device.

Unfortunately I've no idea where is the device dropped. Are you
referring to vhost_net_vq_reset()?
I can fix that part if needed, but won't be able to validate it with KMSAN.


-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg

Re: [PATCH] vhost_net: initialize rx_ring in vhost_net_open()

[Michael S. Tsirkin]

On Thu, Mar 08, 2018 at 04:55:39PM +0100, Alexander Potapenko wrote:
> On Thu, Mar 8, 2018 at 4:33 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Thu, Mar 08, 2018 at 02:37:17PM +0100, Alexander Potapenko wrote:
> >> KMSAN reported a use of uninit memory in vhost_net_buf_unproduce()
> >> while trying to access n->vqs[VHOST_NET_VQ_TX].rx_ring:
> >>
> >> ==================================================================
> >> BUG: KMSAN: use of uninitialized memory in vhost_net_buf_unproduce+0x7bb/0x9a0 drivers/vho
> >> et.c:170
> >> CPU: 0 PID: 3021 Comm: syz-fuzzer Not tainted 4.16.0-rc4+ #3853
> >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
> >> Call Trace:
> >>  __dump_stack lib/dump_stack.c:17 [inline]
> >>  dump_stack+0x185/0x1d0 lib/dump_stack.c:53
> >>  kmsan_report+0x142/0x1f0 mm/kmsan/kmsan.c:1093
> >>  __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
> >>  vhost_net_buf_unproduce+0x7bb/0x9a0 drivers/vhost/net.c:170
> >>  vhost_net_stop_vq drivers/vhost/net.c:974 [inline]
> >>  vhost_net_stop+0x146/0x380 drivers/vhost/net.c:982
> >>  vhost_net_release+0xb1/0x4f0 drivers/vhost/net.c:1015
> >>  __fput+0x49f/0xa00 fs/file_table.c:209
> >>  ____fput+0x37/0x40 fs/file_table.c:243
> >>  task_work_run+0x243/0x2c0 kernel/task_work.c:113
> >>  tracehook_notify_resume include/linux/tracehook.h:191 [inline]
> >>  exit_to_usermode_loop arch/x86/entry/common.c:166 [inline]
> >>  prepare_exit_to_usermode+0x349/0x3b0 arch/x86/entry/common.c:196
> >>  syscall_return_slowpath+0xf3/0x6d0 arch/x86/entry/common.c:265
> >>  do_syscall_64+0x34d/0x450 arch/x86/entry/common.c:292
> >> ...
> >> origin:
> >>  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:303 [inline]
> >>  kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:213
> >>  kmsan_kmalloc_large+0x6f/0xd0 mm/kmsan/kmsan.c:392
> >>  kmalloc_large_node_hook mm/slub.c:1366 [inline]
> >>  kmalloc_large_node mm/slub.c:3808 [inline]
> >>  __kmalloc_node+0x100e/0x1290 mm/slub.c:3818
> >>  kmalloc_node include/linux/slab.h:554 [inline]
> >>  kvmalloc_node+0x1a5/0x2e0 mm/util.c:419
> >>  kvmalloc include/linux/mm.h:541 [inline]
> >>  vhost_net_open+0x64/0x5f0 drivers/vhost/net.c:921
> >>  misc_open+0x7b5/0x8b0 drivers/char/misc.c:154
> >>  chrdev_open+0xc28/0xd90 fs/char_dev.c:417
> >>  do_dentry_open+0xccb/0x1430 fs/open.c:752
> >>  vfs_open+0x272/0x2e0 fs/open.c:866
> >>  do_last fs/namei.c:3378 [inline]
> >>  path_openat+0x49ad/0x6580 fs/namei.c:3519
> >>  do_filp_open+0x267/0x640 fs/namei.c:3553
> >>  do_sys_open+0x6ad/0x9c0 fs/open.c:1059
> >>  SYSC_openat+0xc7/0xe0 fs/open.c:1086
> >>  SyS_openat+0x63/0x90 fs/open.c:1080
> >>  do_syscall_64+0x2f1/0x450 arch/x86/entry/common.c:287
> >> ==================================================================
> >>
> >> Signed-off-by: Alexander Potapenko <glider@google.com>
> >> ---
> >>  drivers/vhost/net.c | 1 +
> >>  1 file changed, 1 insertion(+)
> >>
> >> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> >> index 610cba276d47..60f1080bffc7 100644
> >> --- a/drivers/vhost/net.c
> >> +++ b/drivers/vhost/net.c
> >> @@ -948,6 +948,7 @@ static int vhost_net_open(struct inode *inode, struct file *f)
> >>               n->vqs[i].done_idx = 0;
> >>               n->vqs[i].vhost_hlen = 0;
> >>               n->vqs[i].sock_hlen = 0;
> >> +             n->vqs[i].rx_ring = NULL;
> >>               vhost_net_buf_init(&n->vqs[i].rxq);
> >>       }
> >>       vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX);
> >> --
> >> 2.16.2.395.g2e18187dfd-goog
> >
> >
> > I suspect that's not sufficient. rx ring is tied to the tap device.
> > I think we need to drop it every time we drop the device.
> 
> Unfortunately I've no idea where is the device dropped. Are you
> referring to vhost_net_vq_reset()?
> I can fix that part if needed, but won't be able to validate it with KMSAN.

I see several issues. For example in vhost_net_set_backend
if there's a value then rx ring will point to the
ring of the wrong socket.
Something like the below might help but we really need
documentation of when is rx_ring valid. Is it only valid
when private-data is valid? If yes need to make sure
we reset it with private_data.

Also I see __skb_array_destroy_skb used with ptr_ring which
seems suspicious: how do we know the entries are skbs?

Patch below is on top of yours, and

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

But I really would like Jason to look and come up with a
patch to address all these issues.

---

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 610cba2..7a65b69 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -972,6 +973,7 @@ static struct socket *vhost_net_stop_vq(struct vhost_net *n,
 	vhost_net_disable_vq(n, vq);
 	vq->private_data = NULL;
 	vhost_net_buf_unproduce(nvq);
+	vq->rx_ring = NULL;
 	mutex_unlock(&vq->mutex);
 	return sock;
 }
@@ -1161,8 +1163,6 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
 		vhost_net_disable_vq(n, vq);
 		vq->private_data = sock;
 		vhost_net_buf_unproduce(nvq);
-		if (index == VHOST_NET_VQ_RX)
-			nvq->rx_ring = get_tap_ptr_ring(fd);
 		r = vhost_vq_init_access(vq);
 		if (r)
 			goto err_used;
@@ -1172,6 +1172,10 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
 
 		oldubufs = nvq->ubufs;
 		nvq->ubufs = ubufs;
+		if (index == VHOST_NET_VQ_RX)
+			nvq->rx_ring = get_tap_ptr_ring(fd);
+		else
+			nvq->rx_ring = NULL;
 
 		n->tx_packets = 0;
 		n->tx_zcopy_err = 0;

Re: [PATCH] vhost_net: initialize rx_ring in vhost_net_open()

[Jason Wang]

On 2018年03月09日 00:00, Michael S. Tsirkin wrote:
> On Thu, Mar 08, 2018 at 04:55:39PM +0100, Alexander Potapenko wrote:
>> On Thu, Mar 8, 2018 at 4:33 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
>>> On Thu, Mar 08, 2018 at 02:37:17PM +0100, Alexander Potapenko wrote:
>>>> KMSAN reported a use of uninit memory in vhost_net_buf_unproduce()
>>>> while trying to access n->vqs[VHOST_NET_VQ_TX].rx_ring:
>>>>
>>>> ==================================================================
>>>> BUG: KMSAN: use of uninitialized memory in vhost_net_buf_unproduce+0x7bb/0x9a0 drivers/vho
>>>> et.c:170
>>>> CPU: 0 PID: 3021 Comm: syz-fuzzer Not tainted 4.16.0-rc4+ #3853
>>>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
>>>> Call Trace:
>>>>   __dump_stack lib/dump_stack.c:17 [inline]
>>>>   dump_stack+0x185/0x1d0 lib/dump_stack.c:53
>>>>   kmsan_report+0x142/0x1f0 mm/kmsan/kmsan.c:1093
>>>>   __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
>>>>   vhost_net_buf_unproduce+0x7bb/0x9a0 drivers/vhost/net.c:170
>>>>   vhost_net_stop_vq drivers/vhost/net.c:974 [inline]
>>>>   vhost_net_stop+0x146/0x380 drivers/vhost/net.c:982
>>>>   vhost_net_release+0xb1/0x4f0 drivers/vhost/net.c:1015
>>>>   __fput+0x49f/0xa00 fs/file_table.c:209
>>>>   ____fput+0x37/0x40 fs/file_table.c:243
>>>>   task_work_run+0x243/0x2c0 kernel/task_work.c:113
>>>>   tracehook_notify_resume include/linux/tracehook.h:191 [inline]
>>>>   exit_to_usermode_loop arch/x86/entry/common.c:166 [inline]
>>>>   prepare_exit_to_usermode+0x349/0x3b0 arch/x86/entry/common.c:196
>>>>   syscall_return_slowpath+0xf3/0x6d0 arch/x86/entry/common.c:265
>>>>   do_syscall_64+0x34d/0x450 arch/x86/entry/common.c:292
>>>> ...
>>>> origin:
>>>>   kmsan_save_stack_with_flags mm/kmsan/kmsan.c:303 [inline]
>>>>   kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:213
>>>>   kmsan_kmalloc_large+0x6f/0xd0 mm/kmsan/kmsan.c:392
>>>>   kmalloc_large_node_hook mm/slub.c:1366 [inline]
>>>>   kmalloc_large_node mm/slub.c:3808 [inline]
>>>>   __kmalloc_node+0x100e/0x1290 mm/slub.c:3818
>>>>   kmalloc_node include/linux/slab.h:554 [inline]
>>>>   kvmalloc_node+0x1a5/0x2e0 mm/util.c:419
>>>>   kvmalloc include/linux/mm.h:541 [inline]
>>>>   vhost_net_open+0x64/0x5f0 drivers/vhost/net.c:921
>>>>   misc_open+0x7b5/0x8b0 drivers/char/misc.c:154
>>>>   chrdev_open+0xc28/0xd90 fs/char_dev.c:417
>>>>   do_dentry_open+0xccb/0x1430 fs/open.c:752
>>>>   vfs_open+0x272/0x2e0 fs/open.c:866
>>>>   do_last fs/namei.c:3378 [inline]
>>>>   path_openat+0x49ad/0x6580 fs/namei.c:3519
>>>>   do_filp_open+0x267/0x640 fs/namei.c:3553
>>>>   do_sys_open+0x6ad/0x9c0 fs/open.c:1059
>>>>   SYSC_openat+0xc7/0xe0 fs/open.c:1086
>>>>   SyS_openat+0x63/0x90 fs/open.c:1080
>>>>   do_syscall_64+0x2f1/0x450 arch/x86/entry/common.c:287
>>>> ==================================================================
>>>>
>>>> Signed-off-by: Alexander Potapenko <glider@google.com>
>>>> ---
>>>>   drivers/vhost/net.c | 1 +
>>>>   1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
>>>> index 610cba276d47..60f1080bffc7 100644
>>>> --- a/drivers/vhost/net.c
>>>> +++ b/drivers/vhost/net.c
>>>> @@ -948,6 +948,7 @@ static int vhost_net_open(struct inode *inode, struct file *f)
>>>>                n->vqs[i].done_idx = 0;
>>>>                n->vqs[i].vhost_hlen = 0;
>>>>                n->vqs[i].sock_hlen = 0;
>>>> +             n->vqs[i].rx_ring = NULL;
>>>>                vhost_net_buf_init(&n->vqs[i].rxq);
>>>>        }
>>>>        vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX);
>>>> --
>>>> 2.16.2.395.g2e18187dfd-goog
>>>
>>> I suspect that's not sufficient. rx ring is tied to the tap device.
>>> I think we need to drop it every time we drop the device.
>> Unfortunately I've no idea where is the device dropped. Are you
>> referring to vhost_net_vq_reset()?
>> I can fix that part if needed, but won't be able to validate it with KMSAN.
> I see several issues. For example in vhost_net_set_backend
> if there's a value then rx ring will point to the
> ring of the wrong socket.
> Something like the below might help but we really need
> documentation of when is rx_ring valid. Is it only valid
> when private-data is valid?

I think so, we need keep rx_ring synced with private_data.

> If yes need to make sure
> we reset it with private_data.
>
> Also I see __skb_array_destroy_skb used with ptr_ring which
> seems suspicious: how do we know the entries are skbs?

Good catch, will post an independent patch to fix this.

>
> Patch below is on top of yours, and
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>
> But I really would like Jason to look and come up with a
> patch to address all these issues.
>
> ---
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 610cba2..7a65b69 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -972,6 +973,7 @@ static struct socket *vhost_net_stop_vq(struct vhost_net *n,
>   	vhost_net_disable_vq(n, vq);
>   	vq->private_data = NULL;
>   	vhost_net_buf_unproduce(nvq);
> +	vq->rx_ring = NULL;
>   	mutex_unlock(&vq->mutex);
>   	return sock;
>   }
> @@ -1161,8 +1163,6 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
>   		vhost_net_disable_vq(n, vq);
>   		vq->private_data = sock;
>   		vhost_net_buf_unproduce(nvq);
> -		if (index == VHOST_NET_VQ_RX)
> -			nvq->rx_ring = get_tap_ptr_ring(fd);
>   		r = vhost_vq_init_access(vq);
>   		if (r)
>   			goto err_used;
> @@ -1172,6 +1172,10 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
>   
>   		oldubufs = nvq->ubufs;
>   		nvq->ubufs = ubufs;
> +		if (index == VHOST_NET_VQ_RX)
> +			nvq->rx_ring = get_tap_ptr_ring(fd);
> +		else
> +			nvq->rx_ring = NULL;
>   

Any reason to move those after vhost_net_enable_vq()? And consider we 
won't try to assign rx_ring to TX, the "else" part seems unnecessary.

Thanks

>   		n->tx_packets = 0;
>   		n->tx_zcopy_err = 0;

Re: [PATCH] vhost_net: initialize rx_ring in vhost_net_open()

[Michael S. Tsirkin]

On Fri, Mar 09, 2018 at 10:30:17AM +0800, Jason Wang wrote:
> 
> 
> On 2018年03月09日 00:00, Michael S. Tsirkin wrote:
> > On Thu, Mar 08, 2018 at 04:55:39PM +0100, Alexander Potapenko wrote:
> > > On Thu, Mar 8, 2018 at 4:33 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > > > On Thu, Mar 08, 2018 at 02:37:17PM +0100, Alexander Potapenko wrote:
> > > > > KMSAN reported a use of uninit memory in vhost_net_buf_unproduce()
> > > > > while trying to access n->vqs[VHOST_NET_VQ_TX].rx_ring:
> > > > > 
> > > > > ==================================================================
> > > > > BUG: KMSAN: use of uninitialized memory in vhost_net_buf_unproduce+0x7bb/0x9a0 drivers/vho
> > > > > et.c:170
> > > > > CPU: 0 PID: 3021 Comm: syz-fuzzer Not tainted 4.16.0-rc4+ #3853
> > > > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
> > > > > Call Trace:
> > > > >   __dump_stack lib/dump_stack.c:17 [inline]
> > > > >   dump_stack+0x185/0x1d0 lib/dump_stack.c:53
> > > > >   kmsan_report+0x142/0x1f0 mm/kmsan/kmsan.c:1093
> > > > >   __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
> > > > >   vhost_net_buf_unproduce+0x7bb/0x9a0 drivers/vhost/net.c:170
> > > > >   vhost_net_stop_vq drivers/vhost/net.c:974 [inline]
> > > > >   vhost_net_stop+0x146/0x380 drivers/vhost/net.c:982
> > > > >   vhost_net_release+0xb1/0x4f0 drivers/vhost/net.c:1015
> > > > >   __fput+0x49f/0xa00 fs/file_table.c:209
> > > > >   ____fput+0x37/0x40 fs/file_table.c:243
> > > > >   task_work_run+0x243/0x2c0 kernel/task_work.c:113
> > > > >   tracehook_notify_resume include/linux/tracehook.h:191 [inline]
> > > > >   exit_to_usermode_loop arch/x86/entry/common.c:166 [inline]
> > > > >   prepare_exit_to_usermode+0x349/0x3b0 arch/x86/entry/common.c:196
> > > > >   syscall_return_slowpath+0xf3/0x6d0 arch/x86/entry/common.c:265
> > > > >   do_syscall_64+0x34d/0x450 arch/x86/entry/common.c:292
> > > > > ...
> > > > > origin:
> > > > >   kmsan_save_stack_with_flags mm/kmsan/kmsan.c:303 [inline]
> > > > >   kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:213
> > > > >   kmsan_kmalloc_large+0x6f/0xd0 mm/kmsan/kmsan.c:392
> > > > >   kmalloc_large_node_hook mm/slub.c:1366 [inline]
> > > > >   kmalloc_large_node mm/slub.c:3808 [inline]
> > > > >   __kmalloc_node+0x100e/0x1290 mm/slub.c:3818
> > > > >   kmalloc_node include/linux/slab.h:554 [inline]
> > > > >   kvmalloc_node+0x1a5/0x2e0 mm/util.c:419
> > > > >   kvmalloc include/linux/mm.h:541 [inline]
> > > > >   vhost_net_open+0x64/0x5f0 drivers/vhost/net.c:921
> > > > >   misc_open+0x7b5/0x8b0 drivers/char/misc.c:154
> > > > >   chrdev_open+0xc28/0xd90 fs/char_dev.c:417
> > > > >   do_dentry_open+0xccb/0x1430 fs/open.c:752
> > > > >   vfs_open+0x272/0x2e0 fs/open.c:866
> > > > >   do_last fs/namei.c:3378 [inline]
> > > > >   path_openat+0x49ad/0x6580 fs/namei.c:3519
> > > > >   do_filp_open+0x267/0x640 fs/namei.c:3553
> > > > >   do_sys_open+0x6ad/0x9c0 fs/open.c:1059
> > > > >   SYSC_openat+0xc7/0xe0 fs/open.c:1086
> > > > >   SyS_openat+0x63/0x90 fs/open.c:1080
> > > > >   do_syscall_64+0x2f1/0x450 arch/x86/entry/common.c:287
> > > > > ==================================================================
> > > > > 
> > > > > Signed-off-by: Alexander Potapenko <glider@google.com>
> > > > > ---
> > > > >   drivers/vhost/net.c | 1 +
> > > > >   1 file changed, 1 insertion(+)
> > > > > 
> > > > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> > > > > index 610cba276d47..60f1080bffc7 100644
> > > > > --- a/drivers/vhost/net.c
> > > > > +++ b/drivers/vhost/net.c
> > > > > @@ -948,6 +948,7 @@ static int vhost_net_open(struct inode *inode, struct file *f)
> > > > >                n->vqs[i].done_idx = 0;
> > > > >                n->vqs[i].vhost_hlen = 0;
> > > > >                n->vqs[i].sock_hlen = 0;
> > > > > +             n->vqs[i].rx_ring = NULL;
> > > > >                vhost_net_buf_init(&n->vqs[i].rxq);
> > > > >        }
> > > > >        vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX);
> > > > > --
> > > > > 2.16.2.395.g2e18187dfd-goog
> > > > 
> > > > I suspect that's not sufficient. rx ring is tied to the tap device.
> > > > I think we need to drop it every time we drop the device.
> > > Unfortunately I've no idea where is the device dropped. Are you
> > > referring to vhost_net_vq_reset()?
> > > I can fix that part if needed, but won't be able to validate it with KMSAN.
> > I see several issues. For example in vhost_net_set_backend
> > if there's a value then rx ring will point to the
> > ring of the wrong socket.
> > Something like the below might help but we really need
> > documentation of when is rx_ring valid. Is it only valid
> > when private-data is valid?
> 
> I think so, we need keep rx_ring synced with private_data.
> 
> > If yes need to make sure
> > we reset it with private_data.
> > 
> > Also I see __skb_array_destroy_skb used with ptr_ring which
> > seems suspicious: how do we know the entries are skbs?
> 
> Good catch, will post an independent patch to fix this.
> 
> > 
> > Patch below is on top of yours, and
> > 
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > 
> > But I really would like Jason to look and come up with a
> > patch to address all these issues.
> > 
> > ---
> > 
> > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> > index 610cba2..7a65b69 100644
> > --- a/drivers/vhost/net.c
> > +++ b/drivers/vhost/net.c
> > @@ -972,6 +973,7 @@ static struct socket *vhost_net_stop_vq(struct vhost_net *n,
> >   	vhost_net_disable_vq(n, vq);
> >   	vq->private_data = NULL;
> >   	vhost_net_buf_unproduce(nvq);
> > +	vq->rx_ring = NULL;
> >   	mutex_unlock(&vq->mutex);
> >   	return sock;
> >   }
> > @@ -1161,8 +1163,6 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
> >   		vhost_net_disable_vq(n, vq);
> >   		vq->private_data = sock;
> >   		vhost_net_buf_unproduce(nvq);
> > -		if (index == VHOST_NET_VQ_RX)
> > -			nvq->rx_ring = get_tap_ptr_ring(fd);
> >   		r = vhost_vq_init_access(vq);
> >   		if (r)
> >   			goto err_used;
> > @@ -1172,6 +1172,10 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
> >   		oldubufs = nvq->ubufs;
> >   		nvq->ubufs = ubufs;
> > +		if (index == VHOST_NET_VQ_RX)
> > +			nvq->rx_ring = get_tap_ptr_ring(fd);
> > +		else
> > +			nvq->rx_ring = NULL;
> 
> Any reason to move those after vhost_net_enable_vq()?

Otherwise I see an issue if there is an error and 
we revert the change.

> And consider we won't
> try to assign rx_ring to TX, the "else" part seems unnecessary.
> 
> Thanks

ok, pls pack up all fixes as you see fit and post
a patchset.

> >   		n->tx_packets = 0;
> >   		n->tx_zcopy_err = 0;

Re: [PATCH] vhost_net: initialize rx_ring in vhost_net_open()

[Jason Wang]

On 2018年03月09日 11:29, Michael S. Tsirkin wrote:
> On Fri, Mar 09, 2018 at 10:30:17AM +0800, Jason Wang wrote:
>>
>> On 2018年03月09日 00:00, Michael S. Tsirkin wrote:
>>> On Thu, Mar 08, 2018 at 04:55:39PM +0100, Alexander Potapenko wrote:
>>>> On Thu, Mar 8, 2018 at 4:33 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
>>>>> On Thu, Mar 08, 2018 at 02:37:17PM +0100, Alexander Potapenko wrote:
>>>>>> KMSAN reported a use of uninit memory in vhost_net_buf_unproduce()
>>>>>> while trying to access n->vqs[VHOST_NET_VQ_TX].rx_ring:
>>>>>>
>>>>>> ==================================================================
>>>>>> BUG: KMSAN: use of uninitialized memory in vhost_net_buf_unproduce+0x7bb/0x9a0 drivers/vho
>>>>>> et.c:170
>>>>>> CPU: 0 PID: 3021 Comm: syz-fuzzer Not tainted 4.16.0-rc4+ #3853
>>>>>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
>>>>>> Call Trace:
>>>>>>    __dump_stack lib/dump_stack.c:17 [inline]
>>>>>>    dump_stack+0x185/0x1d0 lib/dump_stack.c:53
>>>>>>    kmsan_report+0x142/0x1f0 mm/kmsan/kmsan.c:1093
>>>>>>    __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
>>>>>>    vhost_net_buf_unproduce+0x7bb/0x9a0 drivers/vhost/net.c:170
>>>>>>    vhost_net_stop_vq drivers/vhost/net.c:974 [inline]
>>>>>>    vhost_net_stop+0x146/0x380 drivers/vhost/net.c:982
>>>>>>    vhost_net_release+0xb1/0x4f0 drivers/vhost/net.c:1015
>>>>>>    __fput+0x49f/0xa00 fs/file_table.c:209
>>>>>>    ____fput+0x37/0x40 fs/file_table.c:243
>>>>>>    task_work_run+0x243/0x2c0 kernel/task_work.c:113
>>>>>>    tracehook_notify_resume include/linux/tracehook.h:191 [inline]
>>>>>>    exit_to_usermode_loop arch/x86/entry/common.c:166 [inline]
>>>>>>    prepare_exit_to_usermode+0x349/0x3b0 arch/x86/entry/common.c:196
>>>>>>    syscall_return_slowpath+0xf3/0x6d0 arch/x86/entry/common.c:265
>>>>>>    do_syscall_64+0x34d/0x450 arch/x86/entry/common.c:292
>>>>>> ...
>>>>>> origin:
>>>>>>    kmsan_save_stack_with_flags mm/kmsan/kmsan.c:303 [inline]
>>>>>>    kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:213
>>>>>>    kmsan_kmalloc_large+0x6f/0xd0 mm/kmsan/kmsan.c:392
>>>>>>    kmalloc_large_node_hook mm/slub.c:1366 [inline]
>>>>>>    kmalloc_large_node mm/slub.c:3808 [inline]
>>>>>>    __kmalloc_node+0x100e/0x1290 mm/slub.c:3818
>>>>>>    kmalloc_node include/linux/slab.h:554 [inline]
>>>>>>    kvmalloc_node+0x1a5/0x2e0 mm/util.c:419
>>>>>>    kvmalloc include/linux/mm.h:541 [inline]
>>>>>>    vhost_net_open+0x64/0x5f0 drivers/vhost/net.c:921
>>>>>>    misc_open+0x7b5/0x8b0 drivers/char/misc.c:154
>>>>>>    chrdev_open+0xc28/0xd90 fs/char_dev.c:417
>>>>>>    do_dentry_open+0xccb/0x1430 fs/open.c:752
>>>>>>    vfs_open+0x272/0x2e0 fs/open.c:866
>>>>>>    do_last fs/namei.c:3378 [inline]
>>>>>>    path_openat+0x49ad/0x6580 fs/namei.c:3519
>>>>>>    do_filp_open+0x267/0x640 fs/namei.c:3553
>>>>>>    do_sys_open+0x6ad/0x9c0 fs/open.c:1059
>>>>>>    SYSC_openat+0xc7/0xe0 fs/open.c:1086
>>>>>>    SyS_openat+0x63/0x90 fs/open.c:1080
>>>>>>    do_syscall_64+0x2f1/0x450 arch/x86/entry/common.c:287
>>>>>> ==================================================================
>>>>>>
>>>>>> Signed-off-by: Alexander Potapenko <glider@google.com>
>>>>>> ---
>>>>>>    drivers/vhost/net.c | 1 +
>>>>>>    1 file changed, 1 insertion(+)
>>>>>>
>>>>>> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
>>>>>> index 610cba276d47..60f1080bffc7 100644
>>>>>> --- a/drivers/vhost/net.c
>>>>>> +++ b/drivers/vhost/net.c
>>>>>> @@ -948,6 +948,7 @@ static int vhost_net_open(struct inode *inode, struct file *f)
>>>>>>                 n->vqs[i].done_idx = 0;
>>>>>>                 n->vqs[i].vhost_hlen = 0;
>>>>>>                 n->vqs[i].sock_hlen = 0;
>>>>>> +             n->vqs[i].rx_ring = NULL;
>>>>>>                 vhost_net_buf_init(&n->vqs[i].rxq);
>>>>>>         }
>>>>>>         vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX);
>>>>>> --
>>>>>> 2.16.2.395.g2e18187dfd-goog
>>>>> I suspect that's not sufficient. rx ring is tied to the tap device.
>>>>> I think we need to drop it every time we drop the device.
>>>> Unfortunately I've no idea where is the device dropped. Are you
>>>> referring to vhost_net_vq_reset()?
>>>> I can fix that part if needed, but won't be able to validate it with KMSAN.
>>> I see several issues. For example in vhost_net_set_backend
>>> if there's a value then rx ring will point to the
>>> ring of the wrong socket.
>>> Something like the below might help but we really need
>>> documentation of when is rx_ring valid. Is it only valid
>>> when private-data is valid?
>> I think so, we need keep rx_ring synced with private_data.
>>
>>> If yes need to make sure
>>> we reset it with private_data.
>>>
>>> Also I see __skb_array_destroy_skb used with ptr_ring which
>>> seems suspicious: how do we know the entries are skbs?
>> Good catch, will post an independent patch to fix this.
>>
>>> Patch below is on top of yours, and
>>>
>>> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>>>
>>> But I really would like Jason to look and come up with a
>>> patch to address all these issues.
>>>
>>> ---
>>>
>>> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
>>> index 610cba2..7a65b69 100644
>>> --- a/drivers/vhost/net.c
>>> +++ b/drivers/vhost/net.c
>>> @@ -972,6 +973,7 @@ static struct socket *vhost_net_stop_vq(struct vhost_net *n,
>>>    	vhost_net_disable_vq(n, vq);
>>>    	vq->private_data = NULL;
>>>    	vhost_net_buf_unproduce(nvq);
>>> +	vq->rx_ring = NULL;
>>>    	mutex_unlock(&vq->mutex);
>>>    	return sock;
>>>    }
>>> @@ -1161,8 +1163,6 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
>>>    		vhost_net_disable_vq(n, vq);
>>>    		vq->private_data = sock;
>>>    		vhost_net_buf_unproduce(nvq);
>>> -		if (index == VHOST_NET_VQ_RX)
>>> -			nvq->rx_ring = get_tap_ptr_ring(fd);
>>>    		r = vhost_vq_init_access(vq);
>>>    		if (r)
>>>    			goto err_used;
>>> @@ -1172,6 +1172,10 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
>>>    		oldubufs = nvq->ubufs;
>>>    		nvq->ubufs = ubufs;
>>> +		if (index == VHOST_NET_VQ_RX)
>>> +			nvq->rx_ring = get_tap_ptr_ring(fd);
>>> +		else
>>> +			nvq->rx_ring = NULL;
>> Any reason to move those after vhost_net_enable_vq()?
> Otherwise I see an issue if there is an error and
> we revert the change.

I see.

>
>> And consider we won't
>> try to assign rx_ring to TX, the "else" part seems unnecessary.
>>
>> Thanks
> ok, pls pack up all fixes as you see fit and post
> a patchset.

Ok.

Thanks

>
>>>    		n->tx_packets = 0;
>>>    		n->tx_zcopy_err = 0;

Re: [PATCH] vhost_net: initialize rx_ring in vhost_net_open()

[Jason Wang]

On 2018年03月08日 23:50, Alexander Potapenko wrote:
> On Thu, Mar 8, 2018 at 4:45 PM, Eric Dumazet<eric.dumazet@gmail.com>  wrote:
>> On 03/08/2018 07:20 AM, Alexander Potapenko wrote:
>>> On Thu, Mar 8, 2018 at 4:15 PM, Eric Dumazet<eric.dumazet@gmail.com>
>>> wrote:
>>>>
>>>> On 03/08/2018 05:37 AM, Alexander Potapenko wrote:
>>>>> KMSAN reported a use of uninit memory in vhost_net_buf_unproduce()
>>>>> while trying to access n->vqs[VHOST_NET_VQ_TX].rx_ring:
>>>>>
>>>>>
>>>>> ==================================================================
>>>>>
>>>>> Signed-off-by: Alexander Potapenko<glider@google.com>
>>>>
>>>> Please identify bug origin with a Fixes: tag
>>> Fixes: 5990a30510ed1 ("tun/tap: use ptr_ring instead of skb_array")
>> Please send a V2 with this added tag. patchwork does not recognize it yet.
> Ok, will do. Thanks for reminding about the tag!

The commit should be c67df11f6e480 ("vhost_net: try batch dequing from 
skb array").

Let me squash this patch into my series.

Thanks