Commit c07fbfd1 authored Aug 10, 2010 by Daniel De Graaf Committed by Linus Torvalds Aug 11, 2010

fbmem: VM_IO set, but not propagated



When we setup up the VMA flags for the mmap flag and we end up using the
fallback mmap functionality we set the vma->vm_flags |= VM_IO.  However we
neglect to propagate the flag to the vma->vm_page_prot.

This bug was found when Linux kernel was running under Xen.  In that
scenario, any page that has VM_IO flag to it, means that it MUST be a
MMIO/VRAM backend memory , _not_ System RAM.  That is what the fbmem.c
does: sets VM_IO, ioremaps the region - everything is peachy.

Well, not exactly.  The vm_page_prot does not get the relevant PTE flags
set (_PAGE_IOMAP) which under Xen is a death-kneel to pages that are
referencing real physical devices but don't have that flag set.

This patch fixes this.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Tested-by: Eamon Walsh <ewalsh@tycho.nsa.gov>
Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Cc: Dave Airlie <airlied@linux.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent daf695fc

drivers/video/fbmem.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -1362,6 +1362,7 @@ fb_mmap(struct file file, struct vm_area_struct vma)
		vma->vm_pgoff = off >> PAGE_SHIFT;
		/* This is an IO map - tell maydump to skip this VMA */
		vma->vm_flags \|= VM_IO \| VM_RESERVED;
		vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
		fb_pgprotect(file, vma, off);
		if (io_remap_pfn_range(vma, vma->vm_start, off >> PAGE_SHIFT,
		vma->vm_end - vma->vm_start, vma->vm_page_prot))

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