From c4f39cba6fd08def0a4491f57566582823751568 Mon Sep 17 00:00:00 2001 From: Hans Verkuil Date: Tue, 13 Nov 2018 09:06:46 -0500 Subject: [PATCH] media: vb2: vb2_mmap: move lock up commit cd26d1c4d1bc947b56ae404998ae2276df7b39b7 upstream. If a filehandle is dup()ped, then it is possible to close it from one fd and call mmap from the other. This creates a race condition in vb2_mmap where it is using queue data that __vb2_queue_free (called from close()) is in the process of releasing. By moving up the mutex_lock(mmap_lock) in vb2_mmap this race is avoided since __vb2_queue_free is called with the same mutex locked. So vb2_mmap now reads consistent buffer data. Signed-off-by: Hans Verkuil Reported-by: syzbot+be93025dd45dccd8923c@syzkaller.appspotmail.com Signed-off-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Greg Kroah-Hartman --- drivers/media/common/videobuf2/videobuf2-core.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c index 1faa64abc74f..07629e7c15be 100644 --- a/drivers/media/common/videobuf2/videobuf2-core.c +++ b/drivers/media/common/videobuf2/videobuf2-core.c @@ -1933,9 +1933,13 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma) return -EINVAL; } } + + mutex_lock(&q->mmap_lock); + if (vb2_fileio_is_active(q)) { dprintk(1, "mmap: file io in progress\n"); - return -EBUSY; + ret = -EBUSY; + goto unlock; } /* @@ -1943,7 +1947,7 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma) */ ret = __find_plane_by_offset(q, off, &buffer, &plane); if (ret) - return ret; + goto unlock; vb = q->bufs[buffer]; @@ -1959,8 +1963,9 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma) return -EINVAL; } - mutex_lock(&q->mmap_lock); ret = call_memop(vb, mmap, vb->planes[plane].mem_priv, vma); + +unlock: mutex_unlock(&q->mmap_lock); if (ret) return ret; -- 2.17.1