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Al Viro authored
commit 55ee64b3 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>
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