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Commit 83e9b7e9 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
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[PATCH] unpaged: private write VM_RESERVED 



The PageReserved removal in 2.6.15-rc1 issued a "deprecated" message when you
tried to mmap or mprotect MAP_PRIVATE PROT_WRITE a VM_RESERVED, and failed
with -EACCES: because do_wp_page lacks the refinement to COW pages in those
areas, nor do we expect to find anonymous pages in them; and it seemed just
bloat to add code for handling such a peculiar case.  But immediately it
caused vbetool and ddcprobe (using lrmi) to fail.

So revert the "deprecated" messages, letting mmap and mprotect succeed.  But
leave do_wp_page's BUG_ON(vma->vm_flags & VM_RESERVED) in place until we've
added the code to do it right: so this particular patch is only good if the
app doesn't really need to write to that private area.

Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent ed5297a9

mm/mmap.c

+0 −11
Original line number Diff line number Diff line
@@ -1076,17 +1076,6 @@ unsigned long do_mmap_pgoff(struct file * file, unsigned long addr, 
		error = file->f_op->mmap(file, vma);

		if (error)

			goto unmap_and_free_vma;

		if ((vma->vm_flags & (VM_SHARED | VM_WRITE | VM_RESERVED))

						== (VM_WRITE | VM_RESERVED)) {

			printk(KERN_WARNING "program %s is using MAP_PRIVATE, "

				"PROT_WRITE mmap of VM_RESERVED memory, which "

				"is deprecated. Please report this to "

				"linux-kernel@vger.kernel.org\n",current->comm);

			if (vma->vm_ops && vma->vm_ops->close)

				vma->vm_ops->close(vma);

			error = -EACCES;

			goto unmap_and_free_vma;

		}

	} else if (vm_flags & VM_SHARED) {

		error = shmem_zero_setup(vma);

		if (error)

mm/mprotect.c

+0 −8
Original line number Diff line number Diff line
@@ -124,14 +124,6 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, 
	 * a MAP_NORESERVE private mapping to writable will now reserve.

	 */

	if (newflags & VM_WRITE) {

		if (oldflags & VM_RESERVED) {

			BUG_ON(oldflags & VM_WRITE);

			printk(KERN_WARNING "program %s is using MAP_PRIVATE, "

				"PROT_WRITE mprotect of VM_RESERVED memory, "

				"which is deprecated. Please report this to "

				"linux-kernel@vger.kernel.org\n",current->comm);

			return -EACCES;

		}

		if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_SHARED|VM_HUGETLB))) {

			charged = nrpages;

			if (security_vm_enough_memory(charged))