From 5a82145cb978983b79993ee1d0b1982f3b80cd9b Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 16 Dec 2012 16:04:46 -0300 Subject: [PATCH] omap_vout: find_vma() needs ->mmap_sem held commit 55ee64b30a38d688232e5eb2860467dddc493573 upstream. 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... Signed-off-by: Al Viro Cc: Sakari Ailus Cc: Laurent Pinchart Cc: Archit Taneja Cc: Prabhakar Lad Signed-off-by: Mauro Carvalho Chehab [bwh: Backported to 3.2: adjust filename] Signed-off-by: Ben Hutchings --- drivers/media/video/omap/omap_vout.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/drivers/media/video/omap/omap_vout.c b/drivers/media/video/omap/omap_vout.c index ee0d0b39cd17..d34521537767 100644 --- a/drivers/media/video/omap/omap_vout.c +++ b/drivers/media/video/omap/omap_vout.c @@ -206,19 +206,21 @@ static u32 omap_vout_uservirt_to_phys(u32 virtp) struct vm_area_struct *vma; struct mm_struct *mm = current->mm; - vma = find_vma(mm, virtp); /* For kernel direct-mapped memory, take the easy way */ - if (virtp >= PAGE_OFFSET) { - physp = virt_to_phys((void *) virtp); - } else if (vma && (vma->vm_flags & VM_IO) && vma->vm_pgoff) { + if (virtp >= PAGE_OFFSET) + return virt_to_phys((void *) virtp); + + down_read(¤t->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 addresses */ physp = (vma->vm_pgoff << PAGE_SHIFT) + (virtp - vma->vm_start); + up_read(¤t->mm->mmap_sem); } else { /* otherwise, use get_user_pages() for general userland pages */ int res, nr_pages = 1; struct page *pages; - down_read(¤t->mm->mmap_sem); res = get_user_pages(current, current->mm, virtp, nr_pages, 1, 0, &pages, NULL); -- 2.39.2