svn commit: r348843 - head/sys/vm

[Andriy Gapon]

On 10/06/2019 06:07, Doug Moore wrote:
> Author: dougm
> Date: Mon Jun 10 03:07:10 2019
> New Revision: 348843
> URL: https://svnweb.freebsd.org/changeset/base/348843
> 
> Log:
>   There are times when a len==0 parameter to mmap is okay. But on a
>   32-bit machine, a len parameter just a few bytes short of 4G, rounded
>   up to a page boundary and hitting zero then, is not okay. Return
>   failure in that case.
>   
>   Reported by: pho
>   Reviewed by: alc, kib (mentor)
>   Tested by: pho
>   Differential Revision: https://reviews.freebsd.org/D20580
> 
> Modified:
>   head/sys/vm/vm_mmap.c
> 
> Modified: head/sys/vm/vm_mmap.c
> ==============================================================================
> --- head/sys/vm/vm_mmap.c	Sun Jun  9 22:55:21 2019	(r348842)
> +++ head/sys/vm/vm_mmap.c	Mon Jun 10 03:07:10 2019	(r348843)
> @@ -257,7 +257,10 @@ kern_mmap(struct thread *td, uintptr_t addr0, size_t s
>  
>  	/* Adjust size for rounding (on both ends). */
>  	size += pageoff;			/* low end... */
> -	size = (vm_size_t) round_page(size);	/* hi end */
> +	/* Check for rounding up to zero. */
> +	if (round_page(size) < size)

Is this guaranteed to work with all compilers?
I think that some smart compilers may think that this condition is impossible.
Are we finally using -fwrapv or something like it for kernel builds?

> +		return (EINVAL);
> +	size = round_page(size);		/* hi end */
>  
>  	/* Ensure alignment is at least a page and fits in a pointer. */
>  	align = flags & MAP_ALIGNMENT_MASK;
> 


-- 
Andriy Gapon