Re: [PATCHv2 17/17] media: v4l2-compat-ioctl32: fix several __user annotations

[Mauro Carvalho Chehab <mchehab@s-opensource.com>]

Em Mon, 16 Apr 2018 14:03:45 +0200
Hans Verkuil <hverkuil@xs4all.nl> escreveu:

> On 04/13/2018 08:07 PM, Mauro Carvalho Chehab wrote:
> > Smatch report several issues with bad __user annotations:
> > 
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:447:21: warning: incorrect type in argument 1 (different address spaces)
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:447:21:    expected void [noderef] <asn:1>*uptr
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:447:21:    got void *<noident>
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:621:21: warning: incorrect type in argument 1 (different address spaces)
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:621:21:    expected void const volatile [noderef] <asn:1>*<noident>
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:621:21:    got struct v4l2_plane [noderef] <asn:1>**<noident>
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:693:13: warning: incorrect type in argument 1 (different address spaces)
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:693:13:    expected void [noderef] <asn:1>*uptr
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:693:13:    got void *[assigned] base
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:871:13: warning: incorrect type in assignment (different address spaces)
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:871:13:    expected struct v4l2_ext_control [noderef] <asn:1>*kcontrols
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:871:13:    got struct v4l2_ext_control *<noident>
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:957:13: warning: incorrect type in assignment (different address spaces)
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:957:13:    expected unsigned char [usertype] *__pu_val
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:957:13:    got void [noderef] <asn:1>*
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:973:13: warning: incorrect type in argument 1 (different address spaces)
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:973:13:    expected void [noderef] <asn:1>*uptr
> >   drivers/media/v4l2-core/v4l2-compat-ioctl32.c:973:13:    got void *[assigned] edid
> > 
> > Fix them.
> > 
> > Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
> > ---
> >  drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 32 ++++++++++++++-------------
> >  1 file changed, 17 insertions(+), 15 deletions(-)
> > 
> > diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> > index d03a44d89649..0b9dfe7dbfe7 100644
> > --- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> > +++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> > @@ -443,8 +443,8 @@ static int put_v4l2_plane32(struct v4l2_plane __user *up,
> >  			return -EFAULT;
> >  		break;
> >  	case V4L2_MEMORY_USERPTR:
> > -		if (get_user(p, &up->m.userptr) ||
> > -		    put_user((compat_ulong_t)ptr_to_compat((__force void *)p),
> > +		if (get_user(p, &up->m.userptr)||
> > +		    put_user((compat_ulong_t)ptr_to_compat((void __user *)p),
> >  			     &up32->m.userptr))
> >  			return -EFAULT;
> >  		break;
> > @@ -587,7 +587,7 @@ static int put_v4l2_buffer32(struct v4l2_buffer __user *kp,
> >  	u32 length;
> >  	enum v4l2_memory memory;
> >  	struct v4l2_plane32 __user *uplane32;
> > -	struct v4l2_plane __user *uplane;
> > +	struct v4l2_plane *uplane;  
> 
> This needs a comment (either here or before the get_user below). It really is a
> pointer to userspace, but since videodev2.h has it without __user (since it is
> copied to kernel space in v4l2-ioctl.c) we need to define it as a regular pointer
> here and cast it to a __user pointer in the put_v4l2_plane32() call.
> 
> This is not trivially obvious, so a comment would help a lot.



> 
> >  	compat_caddr_t p;
> >  	int ret;
> >  
> > @@ -617,15 +617,14 @@ static int put_v4l2_buffer32(struct v4l2_buffer __user *kp,
> >  
> >  		if (num_planes == 0)
> >  			return 0;
> > -
> > -		if (get_user(uplane, ((__force struct v4l2_plane __user **)&kp->m.planes)))
> > +		if (get_user(uplane, &kp->m.planes))
> >  			return -EFAULT;
> >  		if (get_user(p, &up->m.planes))
> >  			return -EFAULT;
> >  		uplane32 = compat_ptr(p);
> >  
> >  		while (num_planes--) {
> > -			ret = put_v4l2_plane32(uplane, uplane32, memory);
> > +			ret = put_v4l2_plane32((void __user *)uplane, uplane32, memory);
> >  			if (ret)
> >  				return ret;
> >  			++uplane;
> > @@ -675,7 +674,7 @@ static int get_v4l2_framebuffer32(struct v4l2_framebuffer __user *kp,
> >  
> >  	if (!access_ok(VERIFY_READ, up, sizeof(*up)) ||
> >  	    get_user(tmp, &up->base) ||
> > -	    put_user((__force void *)compat_ptr(tmp), &kp->base) ||
> > +	    put_user((void __force *)compat_ptr(tmp), &kp->base) ||
> >  	    assign_in_user(&kp->capability, &up->capability) ||
> >  	    assign_in_user(&kp->flags, &up->flags) ||
> >  	    copy_in_user(&kp->fmt, &up->fmt, sizeof(kp->fmt)))
> > @@ -690,7 +689,7 @@ static int put_v4l2_framebuffer32(struct v4l2_framebuffer __user *kp,
> >  
> >  	if (!access_ok(VERIFY_WRITE, up, sizeof(*up)) ||
> >  	    get_user(base, &kp->base) ||
> > -	    put_user(ptr_to_compat(base), &up->base) ||
> > +	    put_user(ptr_to_compat((void __user *)base), &up->base) ||
> >  	    assign_in_user(&up->capability, &kp->capability) ||
> >  	    assign_in_user(&up->flags, &kp->flags) ||
> >  	    copy_in_user(&up->fmt, &kp->fmt, sizeof(kp->fmt)))
> > @@ -857,7 +856,7 @@ static int put_v4l2_ext_controls32(struct file *file,
> >  				   struct v4l2_ext_controls32 __user *up)
> >  {
> >  	struct v4l2_ext_control32 __user *ucontrols;
> > -	struct v4l2_ext_control __user *kcontrols;
> > +	struct v4l2_ext_control *kcontrols;
> >  	u32 count;
> >  	u32 n;
> >  	compat_caddr_t p;
> > @@ -883,10 +882,12 @@ static int put_v4l2_ext_controls32(struct file *file,
> >  		unsigned int size = sizeof(*ucontrols);
> >  		u32 id;
> >  
> > -		if (get_user(id, &kcontrols->id) ||
> > +		if (get_user(id, (unsigned int __user *)&kcontrols->id) ||
> >  		    put_user(id, &ucontrols->id) ||
> > -		    assign_in_user(&ucontrols->size, &kcontrols->size) ||
> > -		    copy_in_user(&ucontrols->reserved2, &kcontrols->reserved2,
> > +		    assign_in_user(&ucontrols->size,
> > +				   (unsigned int __user *)&kcontrols->size) ||
> > +		    copy_in_user(&ucontrols->reserved2,
> > +				 (unsigned int __user *)&kcontrols->reserved2,
> >  				 sizeof(ucontrols->reserved2)))
> >  			return -EFAULT;
> >  
> > @@ -898,7 +899,8 @@ static int put_v4l2_ext_controls32(struct file *file,
> >  		if (ctrl_is_pointer(file, id))
> >  			size -= sizeof(ucontrols->value64);
> >  
> > -		if (copy_in_user(ucontrols, kcontrols, size))
> > +		if (copy_in_user(ucontrols,
> > +			         (unsigned int __user *)kcontrols, size))  
> 
> This is rather ugly. Would it be better to do something like this:
> 
> 	struct v4l2_ext_control __user *kcontrols
> 	struct v4l2_ext_control *kcontrols_tmp;
> 
> 	get_user(kcontrols_tmp, &kp->controls);
> 	kcontrols = (void __user __force *)kcontrols_tmp;

Nah, having two pointers with the same value, one with __user and another
one without it will make it really hard for people to review.

> 
> And then there is no need to change anything else.
> 
> Regardless of the chosen solution, this needs comments to explain what is going
> on here, just as with v4l2_buffer above.

Actually, the problem here happens before that. The problem
here (and on the previous one) is that get_user() expects that
the second argument to be a Kernelspace pointer.

So, in this routine, it does (simplified):

        struct v4l2_ext_control32 __user *ucontrols;
        struct v4l2_ext_control *kcontrols;

...
	get_user(kcontrols, &kp->controls);

Then, every time it needs to get something related to it,
it needs the __user, like here:

	if (get_user(id, (unsigned int __user *)&kcontrols->id)
	...

In this specific case, only copy_in_user() was missing it; all the other
__user casts are there already.


> Note: the whole 'u<foo>' and 'k<foo>' naming is now hopelessly out of date and
> confusing. It should really be '<foo>32' and '<foo>64' to denote 32 bit vs
> 64 bit layout. The pointers are now always in userspace, so 'k<foo>' no longer
> makes sense.

Yes, we need this change, but this should be at a separate patch.

I can do it, after we cleanup v4l2-compat-ioctl32.c from their namespace
mess.


> 
> >  			return -EFAULT;
> >  
> >  		ucontrols++;
> > @@ -954,7 +956,7 @@ static int get_v4l2_edid32(struct v4l2_edid __user *kp,
> >  	    assign_in_user(&kp->start_block, &up->start_block) ||
> >  	    assign_in_user(&kp->blocks, &up->blocks) ||
> >  	    get_user(tmp, &up->edid) ||
> > -	    put_user(compat_ptr(tmp), &kp->edid) ||
> > +	    put_user((void __force *)compat_ptr(tmp), &kp->edid) ||
> >  	    copy_in_user(kp->reserved, up->reserved, sizeof(kp->reserved)))
> >  		return -EFAULT;
> >  	return 0;
> > @@ -970,7 +972,7 @@ static int put_v4l2_edid32(struct v4l2_edid __user *kp,
> >  	    assign_in_user(&up->start_block, &kp->start_block) ||
> >  	    assign_in_user(&up->blocks, &kp->blocks) ||
> >  	    get_user(edid, &kp->edid) ||
> > -	    put_user(ptr_to_compat(edid), &up->edid) ||
> > +	    put_user(ptr_to_compat((void __user *)edid), &up->edid) ||
> >  	    copy_in_user(up->reserved, kp->reserved, sizeof(up->reserved)))
> >  		return -EFAULT;
> >  	return 0;
> >   
> 
> Otherwise this patch looks good.
> 
> Regards,
> 
> 	Hans

Would be ok if I fold (or add as a separate patch) the enclosed diff?

Thanks,
Mauro


diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
index 1057ab8ce2b6..5c3408bdfd89 100644
--- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
+++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
@@ -617,6 +617,15 @@ static int put_v4l2_buffer32(struct v4l2_buffer __user *kp,
 
 		if (num_planes == 0)
 			return 0;
+		/*
+		 * We needed to define uplane without user.
+		 * The reason is that v4l2-ioctl.c copies it from userspace
+		 * into Kernelspace, so it's definition at videodev2.h doesn't
+		 * have an __user markup. That makes get_user() to do wrong
+		 * casts, as pointed by smatch.
+		 * So, instead, declare it as ks, and pass it as an userspace
+		 * pointer to put_v4l2_plane32().
+		 */
 		if (get_user(uplane, &kp->m.planes))
 			return -EFAULT;
 		if (get_user(p, &up->m.planes))
@@ -861,6 +870,15 @@ static int put_v4l2_ext_controls32(struct file *file,
 	u32 n;
 	compat_caddr_t p;
 
+	/*
+	 * We needed to define kcontrols without user.
+	 * The reason is that v4l2-ioctl.c copies it from userspace
+	 * into Kernelspace, so it's definition at videodev2.h doesn't
+	 * have an __user markup. That makes get_user() & friends to do
+	 * wrong casts, as pointed by smatch.
+	 * So, instead, declare it as ks, and pass it as an userspace
+	 * pointer where needed.
+	 */
 	if (!access_ok(VERIFY_WRITE, up, sizeof(*up)) ||
 	    assign_in_user(&up->which, &kp->which) ||
 	    get_user(count, &kp->count) ||