Re: [PATCH] media: v4l2-compat-ioctl32: simplify casts

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

Em Wed, 18 Apr 2018 11:57:13 +0300
Sakari Ailus <sakari.ailus@linux.intel.com> escreveu:

> Hi Mauro,
> 
> On Tue, Apr 17, 2018 at 10:25:37AM -0400, Mauro Carvalho Chehab wrote:
> > Making the cast right for get_user/put_user is not trivial, as
> > it needs to ensure that the types are the correct ones.
> > 
> > Improve it by using macros.
> > 
> > Tested with vivid with:
> > 	$ sudo modprobe vivid no_error_inj=1
> > 	$ v4l2-compliance-32bits -a -s10 >32bits && v4l2-compliance-64bits -a -s10 > 64bits && diff -U0 32bits 64bits
> > 	--- 32bits	2018-04-17 11:18:29.141240772 -0300
> > 	+++ 64bits	2018-04-17 11:18:40.635282341 -0300
> > 	@@ -1 +1 @@
> > 	-v4l2-compliance SHA   : bc71e4a67c6fbc5940062843bc41e7c8679634ce, 32 bits
> > 	+v4l2-compliance SHA   : bc71e4a67c6fbc5940062843bc41e7c8679634ce, 64 bits
> > 
> > Using the latest version of v4l-utils with this patch applied:
> > 	https://patchwork.linuxtv.org/patch/48746/
> > 
> > Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
> > ---
> >  drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 40 ++++++++++++++++++---------
> >  1 file changed, 27 insertions(+), 13 deletions(-)
> > 
> > diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> > index 8c05dd9660d3..d2f0268427c2 100644
> > --- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> > +++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> > @@ -30,6 +30,24 @@
> >  	get_user(__assign_tmp, from) || put_user(__assign_tmp, to);	\
> >  })
> >  
> > +#define get_user_cast(__x, __ptr)					\
> > +({									\
> > +	get_user(__x, (typeof(*__ptr) __user *)(__ptr));		\
> > +})
> > +
> > +#define put_user_force(__x, __ptr)					\
> > +({									\
> > +	put_user((typeof(*__x) __force *)(__x), __ptr);			\
> > +})
> > +
> > +#define assign_in_user_cast(to, from)					\
> > +({									\
> > +	typeof(*from) __assign_tmp;					\
> > +									\
> > +	get_user_cast(__assign_tmp, from) || put_user(__assign_tmp, to);\
> > +})  
> 
> I must say I like the approach. This makes it harder to get things wrong as
> the compiler still does type checking.
> 
> About the naming --- I understand the postfix comes from the modifier used
> in the put_user case but in the others the same approach would lead to
> names such as get_user_user() which would look a bit confusing.

Yes. That's why I used _cast for the version that does the __user cast.

> 
> I presume the patch depends on another patch from you. 

Yes, it comes after the p32/p64 rename.

> Hans had comments on
> that one that I think affect this one as well; 

This patch was added to address Hans comments on patch 4/5. Due to
the renaming, folding it with patch 4/5 is not possible without big
efforts.

> could you add this one to
> the same patchset?

My plan is to apply all those 3 patches together after being reviewed.

The 3 omap3 patches + the 3 ioctl32 patches are altogether here:
	https://git.linuxtv.org/mchehab/experimental.git/log/?h=compile_test_v6b

> 
> > +
> > +
> >  static long native_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> >  {
> >  	long ret = -ENOIOCTLCMD;
> > @@ -543,8 +561,7 @@ static int get_v4l2_buffer32(struct v4l2_buffer __user *p64,
> >  			return -EFAULT;
> >  
> >  		uplane = aux_buf;
> > -		if (put_user((__force struct v4l2_plane *)uplane,
> > -			     &p64->m.planes))
> > +		if (put_user_force(uplane, &p64->m.planes))
> >  			return -EFAULT;
> >  
> >  		while (num_planes--) {
> > @@ -682,7 +699,7 @@ static int get_v4l2_framebuffer32(struct v4l2_framebuffer __user *p64,
> >  
> >  	if (!access_ok(VERIFY_READ, p32, sizeof(*p32)) ||
> >  	    get_user(tmp, &p32->base) ||
> > -	    put_user((void __force *)compat_ptr(tmp), &p64->base) ||
> > +	    put_user_force(compat_ptr(tmp), &p64->base) ||
> >  	    assign_in_user(&p64->capability, &p32->capability) ||
> >  	    assign_in_user(&p64->flags, &p32->flags) ||
> >  	    copy_in_user(&p64->fmt, &p32->fmt, sizeof(p64->fmt)))
> > @@ -831,8 +848,7 @@ static int get_v4l2_ext_controls32(struct file *file,
> >  	if (aux_space < count * sizeof(*kcontrols))
> >  		return -EFAULT;
> >  	kcontrols = aux_buf;
> > -	if (put_user((__force struct v4l2_ext_control *)kcontrols,
> > -		     &p64->controls))
> > +	if (put_user_force(kcontrols, &p64->controls))
> >  		return -EFAULT;
> >  
> >  	for (n = 0; n < count; n++) {
> > @@ -898,12 +914,11 @@ static int put_v4l2_ext_controls32(struct file *file,
> >  		unsigned int size = sizeof(*ucontrols);
> >  		u32 id;
> >  
> > -		if (get_user(id, (unsigned int __user *)&kcontrols->id) ||
> > +		if (get_user_cast(id, &kcontrols->id) ||
> >  		    put_user(id, &ucontrols->id) ||
> > -		    assign_in_user(&ucontrols->size,
> > -				   (unsigned int __user *)&kcontrols->size) ||
> > +		    assign_in_user_cast(&ucontrols->size, &kcontrols->size) ||
> >  		    copy_in_user(&ucontrols->reserved2,
> > -				 (unsigned int __user *)&kcontrols->reserved2,
> > +				 (void __user *)&kcontrols->reserved2,
> >  				 sizeof(ucontrols->reserved2)))
> >  			return -EFAULT;
> >  
> > @@ -916,7 +931,7 @@ static int put_v4l2_ext_controls32(struct file *file,
> >  			size -= sizeof(ucontrols->value64);
> >  
> >  		if (copy_in_user(ucontrols,
> > -			         (unsigned int __user *)kcontrols, size))
> > +			         (void __user *)kcontrols, size))
> >  			return -EFAULT;
> >  
> >  		ucontrols++;
> > @@ -970,10 +985,9 @@ static int get_v4l2_edid32(struct v4l2_edid __user *p64,
> >  	if (!access_ok(VERIFY_READ, p32, sizeof(*p32)) ||
> >  	    assign_in_user(&p64->pad, &p32->pad) ||
> >  	    assign_in_user(&p64->start_block, &p32->start_block) ||
> > -	    assign_in_user(&p64->blocks,
> > -			   (unsigned char __user *)&p32->blocks) ||
> > +	    assign_in_user_cast(&p64->blocks, &p32->blocks) ||
> >  	    get_user(tmp, &p32->edid) ||
> > -	    put_user((void __force *)compat_ptr(tmp), &p64->edid) ||
> > +	    put_user_force(compat_ptr(tmp), &p64->edid) ||
> >  	    copy_in_user(p64->reserved, p32->reserved, sizeof(p64->reserved)))
> >  		return -EFAULT;
> >  	return 0;
> > -- 
> > 2.14.3
> >   
> 



Thanks,
Mauro