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Commit 55ee64b3 authored by Al Viro's avatar Al Viro Committed by Mauro Carvalho Chehab
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[media] omap_vout: find_vma() needs ->mmap_sem held 



Walking rbtree while it's modified is a Bad Idea(tm); besides,
the result of find_vma() can be freed just as it's getting returned
to caller.  Fortunately, it's easy to fix - just take ->mmap_sem a bit
earlier (and don't bother with find_vma() at all if virtp >= PAGE_OFFSET -
in that case we don't even look at its result).

While we are at it, what prevents VIDIOC_PREPARE_BUF calling
v4l_prepare_buf() -> (e.g) vb2_ioctl_prepare_buf() -> vb2_prepare_buf() ->
__buf_prepare() -> __qbuf_userptr() -> vb2_vmalloc_get_userptr() -> find_vma(),
AFAICS without having taken ->mmap_sem anywhere in process?  The code flow
is bloody convoluted and depends on a bunch of things done by initialization,
so I certainly might've missed something...

Cc: stable@vger.kernel.org [2.6.35]
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Cc: Sakari Ailus <sakari.ailus@iki.fi>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Archit Taneja <archit@ti.com>
Cc: Prabhakar Lad <prabhakar.lad@ti.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
parent a0a030bd

drivers/media/platform/omap/omap_vout.c

+7 −5
Original line number Original line Diff line number Diff line
@@ -205,19 +205,21 @@ static u32 omap_vout_uservirt_to_phys(u32 virtp) 
	struct vm_area_struct *vma;

	struct vm_area_struct *vma;

	struct mm_struct *mm = current->mm;

	struct mm_struct *mm = current->mm;





	vma = find_vma(mm, virtp);

	/* For kernel direct-mapped memory, take the easy way */

	/* For kernel direct-mapped memory, take the easy way */

	if (virtp >= PAGE_OFFSET) {

	if (virtp >= PAGE_OFFSET)

		physp = virt_to_phys((void *) virtp);

		return virt_to_phys((void *) virtp);

	} else if (vma && (vma->vm_flags & VM_IO) && vma->vm_pgoff) {



	down_read(&current->mm->mmap_sem);

	vma = find_vma(mm, virtp);

	if (vma && (vma->vm_flags & VM_IO) && vma->vm_pgoff) {

		/* this will catch, kernel-allocated, mmaped-to-usermode

		/* this will catch, kernel-allocated, mmaped-to-usermode

		   addresses */

		   addresses */

		physp = (vma->vm_pgoff << PAGE_SHIFT) + (virtp - vma->vm_start);

		physp = (vma->vm_pgoff << PAGE_SHIFT) + (virtp - vma->vm_start);

		up_read(&current->mm->mmap_sem);

	} else {

	} else {

		/* otherwise, use get_user_pages() for general userland pages */

		/* otherwise, use get_user_pages() for general userland pages */

		int res, nr_pages = 1;

		int res, nr_pages = 1;

		struct page *pages;

		struct page *pages;

		down_read(&current->mm->mmap_sem);





		res = get_user_pages(current, current->mm, virtp, nr_pages, 1,

		res = get_user_pages(current, current->mm, virtp, nr_pages, 1,

				0, &pages, NULL);

				0, &pages, NULL);