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SubjectRe: [PATCH] fix proc_reg_get_unmapped_area()
On Wed, 16 Oct 2013 12:32:40 +0100 "Jan Beulich" <JBeulich@suse.com> wrote:

> Commit c4fe24485729fc2cbff324c111e67a1cc2f9adea ("sparc: fix PCI device
> proc file mmap(2)"), while fixing one problem, introduced two new ones:
> - the function truncates the return value from ->get_unmapped_area() on
> 64-bit architectures,
> - _all_ descendants are now required to set .get_unmapped_area to non-
> NULL, which wasn't necessary before (and shouldn't be).
>
> Both - afaict - are a result from a too simplistic copy'n'paste from
> proc_reg_mmap() done in that change.
>
> This likely also addresses reports like the one at
> http://linux-kernel.2935.n7.nabble.com/mmap-for-proc-vmcore-broken-since-3-12-rc1-td729326.html.
>
> ...
>
> --- 3.12-rc5/fs/proc/inode.c
> +++ 3.12-rc5-proc-get-unmapped-area/fs/proc/inode.c
> @@ -288,12 +288,12 @@ static int proc_reg_mmap(struct file *fi
> static unsigned long proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr, unsigned long len, unsigned long pgoff, unsigned long flags)
> {
> struct proc_dir_entry *pde = PDE(file_inode(file));
> - int rv = -EIO;
> - unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
> + unsigned long rv = -EIO;
> +
> if (use_pde(pde)) {
> - get_unmapped_area = pde->proc_fops->get_unmapped_area;
> - if (get_unmapped_area)
> - rv = get_unmapped_area(file, orig_addr, len, pgoff, flags);
> + rv = (pde->proc_fops->get_unmapped_area
> + ?: current->mm->get_unmapped_area)(file, orig_addr, len,
> + pgoff, flags);
> unuse_pde(pde);
> }
> return rv;

I think these two patches will address the problems:

http://ozlabs.org/~akpm/mmots/broken-out/procfs-fix-unintended-truncation-of-returned-mapped-address.patch
http://ozlabs.org/~akpm/mmots/broken-out/procfs-call-default-get_unmapped_area-on-mmu-present-architectures.patch

I'll be sending those Linuswards today. Please check them. (I think
your version would break the nommu build).



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