Re: [PATCH] hugetlbfs: Fix integer overflow check in hugetlbfs_file_mmap()

[David Hildenbrand <david@redhat.com>]

On 10.07.23 10:32, Linke Li wrote:
> From: Linke Li <lilinke99@gmail.com>
> 
> 	vma_len = (loff_t)(vma->vm_end - vma->vm_start);
> 	len = vma_len + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
> 	/* check for overflow */
> 	if (len < vma_len)
> 		return -EINVAL;
> 
> The existing code includes an integer overflow check, which indicates
> that the variable len has the potential to overflow, leading to undefined
>   behavior according to the C standard. However, both GCC and Clang
> compilers may eliminate this overflow check based on the assumption
> that there will be no undefined behavior. Although the Linux kernel
> disables these optimizations by using the -fno-strict-overflow option,
> there is still a risk if the compilers make mistakes in the future.

So we're adding code to handle eventual future compiler bugs? That 
sounds wrong, but maybe I misunderstood the problem you are trying to solve?

-- 
Cheers,

David / dhildenb