From: Hans Verkuil <hverkuil@xs4all.nl>
To: Linux Media Mailing List <linux-media@vger.kernel.org>
Subject: [PATCH] vb2: vb2_mmap: move lock up
Date: Tue, 13 Nov 2018 15:06:46 +0100 [thread overview]
Message-ID: <71cb9482-fa06-def3-115e-105a0e0f3aec@xs4all.nl> (raw)
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 <hverkuil@xs4all.nl>
Reported-by: syzbot+be93025dd45dccd8923c@syzkaller.appspotmail.com
---
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 c49c67473408..03954c13024c 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -2120,9 +2120,13 @@ 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;
}
/*
@@ -2130,7 +2134,7 @@ 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];
@@ -2146,8 +2150,9 @@ 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;
--
2.19.1
reply other threads:[~2018-11-14 0:05 UTC|newest]
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