linux-kernel - Re: mmap for /proc/vmcore broken since 3.12-rc1

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Date:	Sat, 12 Oct 2013 23:32:50 +0300
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
Cc:	Michael Holzheu <holzheu@...ux.vnet.ibm.com>,
	"David S. Miller" <davem@...emloft.net>,
	Vivek Goyal <vgoyal@...hat.com>,
	Jan Willeke <willeke@...ibm.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	kexec@...ts.infradead.org
Subject: Re: mmap for /proc/vmcore broken since 3.12-rc1

On Wed, Oct 09, 2013 at 07:14:55PM +0900, HATAYAMA Daisuke wrote:
> Hello,
> 
> (2013/10/08 21:49), Alexey Dobriyan wrote:
> > On Mon, Oct 7, 2013 at 5:42 AM, HATAYAMA Daisuke
> > <d.hatayama@...fujitsu.com> wrote:
> >
> >> +static unsigned long
> >> +get_unmapped_area_vmcore(struct file *filp, unsigned long addr,
> >> +                        unsigned long len, unsigned long pgoff,
> >> +                        unsigned long flags)
> >> +{
> >> +#ifdef CONFIG_MMU
> >> +       return current->mm->get_unmapped_area(filp, addr, len, pgoff,
> >> flags);
> >> +#else
> >> +       return -EIO;
> >> +#endif
> >> +}
> >> +
> >>   static const struct file_operations proc_vmcore_operations = {
> >>          .read           = read_vmcore,
> >>          .llseek         = default_llseek,
> >>          .mmap           = mmap_vmcore,
> >> +       .get_unmapped_area = get_unmapped_area_vmcore,
> >
> > I think current->mm->get_unmapped_area should be used by core proc code.
> 
> What do you actually suggest here? You mean moving this code in proc code?
> I don't think you suggest so.

Please, try this patch, I don't have kexec setup handy.

--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -291,7 +291,11 @@ static unsigned long proc_reg_get_unmapped_area(struct file *file, unsigned long
 	int rv = -EIO;
 	unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
 	if (use_pde(pde)) {
-		get_unmapped_area = pde->proc_fops->get_unmapped_area;
+		get_unmapped_area = current->mm->get_unmapped_area;
+#ifdef CONFIG_MMU
+		if (pde->proc_fops->get_unmapped_area)
+			get_unmapped_area = pde->proc_fops->get_unmapped_area;
+#endif
 		if (get_unmapped_area)
 			rv = get_unmapped_area(file, orig_addr, len, pgoff, flags);
 		unuse_pde(pde);
--
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