[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: Al 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: Mauro Carvalho Chehab <mchehab@redhat.com>
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@ -205,19 +205,21 @@ static u32 omap_vout_uservirt_to_phys(u32 virtp)
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struct vm_area_struct *vma;
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struct mm_struct *mm = current->mm;
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vma = find_vma(mm, virtp);
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/* For kernel direct-mapped memory, take the easy way */
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if (virtp >= PAGE_OFFSET) {
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physp = virt_to_phys((void *) virtp);
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} else if (vma && (vma->vm_flags & VM_IO) && vma->vm_pgoff) {
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if (virtp >= PAGE_OFFSET)
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return virt_to_phys((void *) virtp);
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down_read(¤t->mm->mmap_sem);
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vma = find_vma(mm, virtp);
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if (vma && (vma->vm_flags & VM_IO) && vma->vm_pgoff) {
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/* this will catch, kernel-allocated, mmaped-to-usermode
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addresses */
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physp = (vma->vm_pgoff << PAGE_SHIFT) + (virtp - vma->vm_start);
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up_read(¤t->mm->mmap_sem);
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} else {
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/* otherwise, use get_user_pages() for general userland pages */
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int res, nr_pages = 1;
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struct page *pages;
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down_read(¤t->mm->mmap_sem);
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res = get_user_pages(current, current->mm, virtp, nr_pages, 1,
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0, &pages, NULL);
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