NAK: [PATCH][SRU][WILY][XENIAL][YAKKETY][V2] UBUNTU: SAUCE: mm/mmap: fix oopsing on remap_file_pages aufs mmap: bugfix, mainly for linux-4.5-rc5, remap_file_pages(2) emulation

[Kamal Mostafa]

On Fri, May 20, 2016 at 03:16:25PM +0100, Colin King wrote:
> From: "J. R. Okajima" <hooanon05g at gmail.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1558120
> 
> This is essentially same to the past commit for aufs3.9
>   f84155f 2014-06-11 aufs mmap: bugfix remap_file_pages(2)
> 
> But the remap_file_pages(2) changed drastically in linux-4.0 by
>   c8d78c1 2015-02-10 mm: replace remap_file_pages() syscall with emulation
> and then a bugfix was commited in linux-4.5-rc5.
>   48f7df3 2016-02-18 mm: fix regression in remap_file_pages() emulation
> 
> After the bugfix in 4.5-rc5, Colin Ian King found and reported this aufs
> bug.
> 
> See-also: https://github.com/sfjro/aufs4-linux/pull/1
> Signed-off-by: J. R. Okajima <hooanon05g at gmail.com>
> (cherry picked from commit ea98b4d56b605fc4fc35a9f05c597e36308197b0)

NAK, because that SHA does not appear in mainline linux, so needs a URL
to the repo from whence it came.  Colin, please correct and resubmit!

 -Kamal


> Signed-off-by: Colin Ian King <colin.king at canonical.com>
> ---
>  mm/mmap.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index f8854ad..f8c73f6 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2630,6 +2630,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
>  	struct vm_area_struct *vma;
>  	unsigned long populate = 0;
>  	unsigned long ret = -EINVAL;
> +	struct file *file, *prfile;
>  
>  	pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. "
>  			"See Documentation/vm/remap_file_pages.txt.\n",
> @@ -2698,9 +2699,26 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
>  	}
>  
>  	vma_get_file(vma);
> +	file = vma->vm_file;
> +	prfile = vma->vm_prfile;
>  	ret = do_mmap_pgoff(vma->vm_file, start, size,
>  			prot, flags, pgoff, &populate);
> -	vma_fput(vma);
> +	if (!IS_ERR_VALUE(ret) && file && prfile) {
> +		struct vm_area_struct *new_vma;
> +
> +		new_vma = find_vma(mm, ret);
> +		if (!new_vma->vm_prfile)
> +			new_vma->vm_prfile = prfile;
> +		if (new_vma != vma)
> +			get_file(prfile);
> +	}
> +	/*
> +	 * two fput()s instead of vma_fput(vma),
> +	 * coz vma may not be available anymore.
> +	 */
> +	fput(file);
> +	if (prfile)
> +		fput(prfile);
>  out:
>  	up_write(&mm->mmap_sem);
>  	if (populate)
> -- 
> 2.8.1
> 
> 
> -- 
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