vduse: Fix a possible warning in vduse_create_dev()

[PATCH] vduse: Fix a possible warning in vduse_create_dev()

Posted by Harshit Mogalapalli 2 years, 9 months ago

As 'dev->vq_num' is user-controlled data, if user tries to allocate
memory larger than(>=) MAX_ORDER, then kcalloc() will fail, it
creates a stack trace and messes up dmesg with a warning.

Call trace:
-> vduse_ioctl
--> vduse_create_dev
'config->vq_num' is user data as it comes from ioctl, which is
assigned to 'dev->vq_num'.

Add __GFP_NOWARN in order to avoid too large allocation warning.
This is detected by static analysis using smatch.

Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
---
 drivers/vdpa/vdpa_user/vduse_dev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
index 35dceee3ed56..5e9546b16165 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -1512,7 +1512,8 @@ static int vduse_create_dev(struct vduse_dev_config *config,
 	dev->config_size = config->config_size;
 	dev->vq_align = config->vq_align;
 	dev->vq_num = config->vq_num;
-	dev->vqs = kcalloc(dev->vq_num, sizeof(*dev->vqs), GFP_KERNEL);
+	dev->vqs = kcalloc(dev->vq_num, sizeof(*dev->vqs),
+			   GFP_KERNEL | __GFP_NOWARN);
 	if (!dev->vqs)
 		goto err_vqs;
 
-- 
2.38.1

Re: [PATCH] vduse: Fix a possible warning in vduse_create_dev()

Posted by Michael S. Tsirkin 2 years, 9 months ago

On Fri, Nov 25, 2022 at 07:59:58PM -0800, Harshit Mogalapalli wrote:
> As 'dev->vq_num' is user-controlled data, if user tries to allocate
> memory larger than(>=) MAX_ORDER, then kcalloc() will fail, it
> creates a stack trace and messes up dmesg with a warning.
> 
> Call trace:
> -> vduse_ioctl
> --> vduse_create_dev
> 'config->vq_num' is user data as it comes from ioctl, which is
> assigned to 'dev->vq_num'.
> 
> Add __GFP_NOWARN in order to avoid too large allocation warning.
> This is detected by static analysis using smatch.
> 
> Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
> ---
>  drivers/vdpa/vdpa_user/vduse_dev.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index 35dceee3ed56..5e9546b16165 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -1512,7 +1512,8 @@ static int vduse_create_dev(struct vduse_dev_config *config,
>  	dev->config_size = config->config_size;
>  	dev->vq_align = config->vq_align;
>  	dev->vq_num = config->vq_num;
> -	dev->vqs = kcalloc(dev->vq_num, sizeof(*dev->vqs), GFP_KERNEL);
> +	dev->vqs = kcalloc(dev->vq_num, sizeof(*dev->vqs),
> +			   GFP_KERNEL | __GFP_NOWARN);
>  	if (!dev->vqs)
>  		goto err_vqs;

This is insufficient - the real source of the problem is that
vq_num is not validated.
The thing to do is to validate config and limit vq_num to 0xffff;


> -- 
> 2.38.1

Re: [PATCH] vduse: Fix a possible warning in vduse_create_dev()

Posted by Harshit Mogalapalli 2 years, 9 months ago

Hi Micheal,

On 27/11/22 4:52 am, Michael S. Tsirkin wrote:
> On Fri, Nov 25, 2022 at 07:59:58PM -0800, Harshit Mogalapalli wrote:
>> As 'dev->vq_num' is user-controlled data, if user tries to allocate
>> memory larger than(>=) MAX_ORDER, then kcalloc() will fail, it
>> creates a stack trace and messes up dmesg with a warning.
>>
>> Call trace:
>> -> vduse_ioctl
>> --> vduse_create_dev
>> 'config->vq_num' is user data as it comes from ioctl, which is
>> assigned to 'dev->vq_num'.
>>
>> Add __GFP_NOWARN in order to avoid too large allocation warning.
>> This is detected by static analysis using smatch.
>>
>> Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
>> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
>> ---
>>   drivers/vdpa/vdpa_user/vduse_dev.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
>> index 35dceee3ed56..5e9546b16165 100644
>> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
>> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
>> @@ -1512,7 +1512,8 @@ static int vduse_create_dev(struct vduse_dev_config *config,
>>   	dev->config_size = config->config_size;
>>   	dev->vq_align = config->vq_align;
>>   	dev->vq_num = config->vq_num;
>> -	dev->vqs = kcalloc(dev->vq_num, sizeof(*dev->vqs), GFP_KERNEL);
>> +	dev->vqs = kcalloc(dev->vq_num, sizeof(*dev->vqs),
>> +			   GFP_KERNEL | __GFP_NOWARN);
>>   	if (!dev->vqs)
>>   		goto err_vqs;
> 

Thanks for checking the patch.

> This is insufficient - the real source of the problem is that
> vq_num is not validated.
> The thing to do is to validate config and limit vq_num to 0xffff;
> 

1557 static long vduse_ioctl(struct file *file, unsigned int cmd,
1558                         unsigned long arg)
1559 {
1560         int ret;
1561         void __user *argp = (void __user *)arg;
1564         mutex_lock(&vduse_lock);
1565         switch (cmd) {
              ....
1584         case VDUSE_CREATE_DEV: {
1585                 struct vduse_dev_config config;
1587                 void *buf;
1588
1589                 ret = -EFAULT;
1590                 if (copy_from_user(&config, argp, size))
1591                         break;
1592
1593                 ret = -EINVAL;
1594                 if (vduse_validate_config(&config) == false)
1595                         break;
1596
1597                 buf = vmemdup_user(argp + size, config.config_size);
1598                 if (IS_ERR(buf)) {
1599                         ret = PTR_ERR(buf);
1600                         break;
1601                 }
1602                 config.name[VDUSE_NAME_MAX - 1] = '\0';
1603                 ret = vduse_create_dev(&config, buf, 
control->api_version);
1604                 if (ret)
1605                         kvfree(buf);
1606                 break;
1607         }

we have vduse_validate_config() being called in vduse_ioctl() which is 
the caller of vduse_create_dev(), so validate_config() is not necessary 
in vduse_create_dev() ?

Thanks,
Harshit

> 
>> -- 
>> 2.38.1
>

Re: [PATCH] vduse: Fix a possible warning in vduse_create_dev()

Posted by Michael S. Tsirkin 2 years, 9 months ago

On Sun, Nov 27, 2022 at 08:16:24AM +0530, Harshit Mogalapalli wrote:
> Hi Micheal,
> 
> On 27/11/22 4:52 am, Michael S. Tsirkin wrote:
> > On Fri, Nov 25, 2022 at 07:59:58PM -0800, Harshit Mogalapalli wrote:
> > > As 'dev->vq_num' is user-controlled data, if user tries to allocate
> > > memory larger than(>=) MAX_ORDER, then kcalloc() will fail, it
> > > creates a stack trace and messes up dmesg with a warning.
> > > 
> > > Call trace:
> > > -> vduse_ioctl
> > > --> vduse_create_dev
> > > 'config->vq_num' is user data as it comes from ioctl, which is
> > > assigned to 'dev->vq_num'.
> > > 
> > > Add __GFP_NOWARN in order to avoid too large allocation warning.
> > > This is detected by static analysis using smatch.
> > > 
> > > Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
> > > Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
> > > ---
> > >   drivers/vdpa/vdpa_user/vduse_dev.c | 3 ++-
> > >   1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> > > index 35dceee3ed56..5e9546b16165 100644
> > > --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> > > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> > > @@ -1512,7 +1512,8 @@ static int vduse_create_dev(struct vduse_dev_config *config,
> > >   	dev->config_size = config->config_size;
> > >   	dev->vq_align = config->vq_align;
> > >   	dev->vq_num = config->vq_num;
> > > -	dev->vqs = kcalloc(dev->vq_num, sizeof(*dev->vqs), GFP_KERNEL);
> > > +	dev->vqs = kcalloc(dev->vq_num, sizeof(*dev->vqs),
> > > +			   GFP_KERNEL | __GFP_NOWARN);
> > >   	if (!dev->vqs)
> > >   		goto err_vqs;
> > 
> 
> Thanks for checking the patch.
> 
> > This is insufficient - the real source of the problem is that
> > vq_num is not validated.
> > The thing to do is to validate config and limit vq_num to 0xffff;
> > 
> 
> 1557 static long vduse_ioctl(struct file *file, unsigned int cmd,
> 1558                         unsigned long arg)
> 1559 {
> 1560         int ret;
> 1561         void __user *argp = (void __user *)arg;
> 1564         mutex_lock(&vduse_lock);
> 1565         switch (cmd) {
>              ....
> 1584         case VDUSE_CREATE_DEV: {
> 1585                 struct vduse_dev_config config;
> 1587                 void *buf;
> 1588
> 1589                 ret = -EFAULT;
> 1590                 if (copy_from_user(&config, argp, size))
> 1591                         break;
> 1592
> 1593                 ret = -EINVAL;
> 1594                 if (vduse_validate_config(&config) == false)
> 1595                         break;
> 1596
> 1597                 buf = vmemdup_user(argp + size, config.config_size);
> 1598                 if (IS_ERR(buf)) {
> 1599                         ret = PTR_ERR(buf);
> 1600                         break;
> 1601                 }
> 1602                 config.name[VDUSE_NAME_MAX - 1] = '\0';
> 1603                 ret = vduse_create_dev(&config, buf,
> control->api_version);
> 1604                 if (ret)
> 1605                         kvfree(buf);
> 1606                 break;
> 1607         }
> 
> we have vduse_validate_config() being called in vduse_ioctl() which is the
> caller of vduse_create_dev(), so validate_config() is not necessary in
> vduse_create_dev() ?
> 
> Thanks,
> Harshit

OK but I don't see vduse_validate_config checking vq_num.

> > 
> > > -- 
> > > 2.38.1
> >

Re: [PATCH] vduse: Fix a possible warning in vduse_create_dev()

Posted by Harshit Mogalapalli 2 years, 9 months ago

Hi Micheal,

On 27/11/22 10:04 pm, Michael S. Tsirkin wrote:
> On Sun, Nov 27, 2022 at 08:16:24AM +0530, Harshit Mogalapalli wrote:
>> Hi Micheal,
>>
>> On 27/11/22 4:52 am, Michael S. Tsirkin wrote:
>>> On Fri, Nov 25, 2022 at 07:59:58PM -0800, Harshit Mogalapalli wrote:
>>>> As 'dev->vq_num' is user-controlled data, if user tries to allocate
>>>> memory larger than(>=) MAX_ORDER, then kcalloc() will fail, it
>>>> creates a stack trace and messes up dmesg with a warning.
>>>>
>>>> Call trace:
>>>> -> vduse_ioctl
>>>> --> vduse_create_dev
>>>> 'config->vq_num' is user data as it comes from ioctl, which is
>>>> assigned to 'dev->vq_num'.
>>>>
>>>> Add __GFP_NOWARN in order to avoid too large allocation warning.
>>>> This is detected by static analysis using smatch.
>>>>
>>>> Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
>>>> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
>>>> ---
>>>>    drivers/vdpa/vdpa_user/vduse_dev.c | 3 ++-
>>>>    1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
>>>> index 35dceee3ed56..5e9546b16165 100644
>>>> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
>>>> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
>>>> @@ -1512,7 +1512,8 @@ static int vduse_create_dev(struct vduse_dev_config *config,
>>>>    	dev->config_size = config->config_size;
>>>>    	dev->vq_align = config->vq_align;
>>>>    	dev->vq_num = config->vq_num;
>>>> -	dev->vqs = kcalloc(dev->vq_num, sizeof(*dev->vqs), GFP_KERNEL);
>>>> +	dev->vqs = kcalloc(dev->vq_num, sizeof(*dev->vqs),
>>>> +			   GFP_KERNEL | __GFP_NOWARN);
>>>>    	if (!dev->vqs)
>>>>    		goto err_vqs;
>>>
>>
>> Thanks for checking the patch.
>>
>>> This is insufficient - the real source of the problem is that
>>> vq_num is not validated.
>>> The thing to do is to validate config and limit vq_num to 0xffff;
>>>
>>
>> 1557 static long vduse_ioctl(struct file *file, unsigned int cmd,
>> 1558                         unsigned long arg)
>> 1559 {
>> 1560         int ret;
>> 1561         void __user *argp = (void __user *)arg;
>> 1564         mutex_lock(&vduse_lock);
>> 1565         switch (cmd) {
>>               ....
>> 1584         case VDUSE_CREATE_DEV: {
>> 1585                 struct vduse_dev_config config;
>> 1587                 void *buf;
>> 1588
>> 1589                 ret = -EFAULT;
>> 1590                 if (copy_from_user(&config, argp, size))
>> 1591                         break;
>> 1592
>> 1593                 ret = -EINVAL;
>> 1594                 if (vduse_validate_config(&config) == false)
>> 1595                         break;
>> 1596
>> 1597                 buf = vmemdup_user(argp + size, config.config_size);
>> 1598                 if (IS_ERR(buf)) {
>> 1599                         ret = PTR_ERR(buf);
>> 1600                         break;
>> 1601                 }
>> 1602                 config.name[VDUSE_NAME_MAX - 1] = '\0';
>> 1603                 ret = vduse_create_dev(&config, buf,
>> control->api_version);
>> 1604                 if (ret)
>> 1605                         kvfree(buf);
>> 1606                 break;
>> 1607         }
>>
>> we have vduse_validate_config() being called in vduse_ioctl() which is the
>> caller of vduse_create_dev(), so validate_config() is not necessary in
>> vduse_create_dev() ?
>>
>> Thanks,
>> Harshit
> 
> OK but I don't see vduse_validate_config checking vq_num.
> 

right, I have added a limit of 0xffff to vq_num as you suggested in V2.

The reason for keeping the limit as 0xffff is the max number of virt 
queues is the size of vring buffer?

Thanks,
Harshit

>>>
>>>> -- 
>>>> 2.38.1
>>>
>

Re: [PATCH] vduse: Fix a possible warning in vduse_create_dev()

Posted by Dan Carpenter 2 years, 9 months ago

Btw, after you add the check to vduse_validate_config() you can test
that it silences the Smatch warning by doing:

kchecker --info drivers/vdpa/vdpa_user/vduse_dev.c | tee out
~/smatch/smatch_data/db/reload_partial.sh out
kchecker drivers/vdpa/vdpa_user/vduse_dev.c

You might need to do a second --info and reload for the changes to
propagate.

regards,
dan carpenter