diff options
| author | Al Viro <viro@ZenIV.linux.org.uk> | 2012-12-16 16:04:46 -0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-04-14 06:44:33 -0700 |
| commit | 915b4b0510b5f483fd46db9154c8dc1ee9e38ddf (patch) | |
| tree | ab25a83b7b491eb0809ec02762f3f7a503862af6 | |
| parent | ac871a8a93556bb96e6d11931c4568f60546c50f (diff) | |
| download | lwn-915b4b0510b5f483fd46db9154c8dc1ee9e38ddf.tar.gz lwn-915b4b0510b5f483fd46db9154c8dc1ee9e38ddf.zip | |
media: 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 <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>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Jianguo Wu <wujianguo@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/media/video/omap/omap_vout.c | 12 |
1 files changed, 7 insertions, 5 deletions
diff --git a/drivers/media/video/omap/omap_vout.c b/drivers/media/video/omap/omap_vout.c index 88cf9d952631..89f354e8f641 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); |