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Message-ID: <20230724185900.GA3240@monkey>
Date: Mon, 24 Jul 2023 11:59:00 -0700
From: Mike Kravetz <mike.kravetz@...cle.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: Linke Li <lilinke99@...mail.com>, linux-mm@...ck.org,
muchun.song@...ux.dev, nathan@...nel.org, ndesaulniers@...gle.com,
trix@...hat.com, linux-kernel@...r.kernel.org,
llvm@...ts.linux.dev, dan.carpenter@...aro.org,
Linke Li <lilinke99@...il.com>
Subject: Re: [PATCH v3] hugetlbfs: Fix integer overflow check in
hugetlbfs_file_mmap()
On 07/24/23 04:47, Matthew Wilcox wrote:
> On Thu, Jul 20, 2023 at 10:49:52PM +0800, Linke Li wrote:
> > +++ b/fs/hugetlbfs/inode.c
> > @@ -154,10 +154,7 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
> > if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT))
> > return -EINVAL;
> >
> > - 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)
> > + if (check_add_overflow(vma_len, (loff_t)vma->vm_pgoff << PAGE_SHIFT, &len))
> > return -EINVAL;
>
> Doesn't this check duplicate that performed by file_mmap_ok()? Can't we
> just delete the check, or is there a code path that leads here while
> avoiding file_mmap_ok()?
Thanks for pointing that out.
Yes, from my reading/understanding that is a repeat.
It looks like most of the overflow checking in hugetlbfs_file_mmap is a
repeat of checks done previously. I remember adding this code in
response to a checker or someone pointing out the potential for overflow:
/*
* page based offset in vm_pgoff could be sufficiently large to
* overflow a loff_t when converted to byte offset. This can
* only happen on architectures where sizeof(loff_t) ==
* sizeof(unsigned long). So, only check in those instances.
*/
if (sizeof(unsigned long) == sizeof(loff_t)) {
if (vma->vm_pgoff & PGOFF_LOFFT_MAX)
return -EINVAL;
}
However, file_mmap_ok seems to handle this as well. The important thing that
needs to be done in hugetlbfs_file_mmap is checking for huge page alignment.
I have added this code cleanup to my list if someone does not do it first.
--
Mike Kravetz
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