On Mon, 18 Jul 2016 22:01:29 +0800
Minfei Huang <mnfhuang@xxxxxxxxx> wrote:
> We do a lot of memory allocation in function init_vq, and don't handle
> the allocation failure properly. Then this function will return 0,
> although initialization fails due to lacking memory. At that moment,
> kernel will panic in guest machine, if virtio is used to drive disk.
>
> To fix this bug, we should take care of allocation failure, and return
> correct value to let caller know what happen.
>
> Tested-by: Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>
> Signed-off-by: Minfei Huang <minfei.hmf@xxxxxxxxxxxxxxx>
> Signed-off-by: Minfei Huang <mnghuan@xxxxxxxxx>
> ---
> v1:
> - Refactor the patch to make code more readable
> ---
> drivers/block/virtio_blk.c | 32 +++++++++++---------------------
> 1 file changed, 11 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 42758b5..d920512 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -381,9 +381,9 @@ static int init_vq(struct virtio_blk *vblk)
> {
> int err = 0;
> int i;
> - vq_callback_t **callbacks;
> - const char **names;
> - struct virtqueue **vqs;
> + vq_callback_t **callbacks = NULL;
> + const char **names = NULL;
> + struct virtqueue **vqs = NULL;
If you init the variables to NULL anyway...
> unsigned short num_vqs;
> struct virtio_device *vdev = vblk->vdev;
>
> @@ -394,22 +394,16 @@ static int init_vq(struct virtio_blk *vblk)
> num_vqs = 1;
>
...just do
err = -ENOMEM;
here and...
> vblk->vqs = kmalloc(sizeof(*vblk->vqs) * num_vqs, GFP_KERNEL);
> - if (!vblk->vqs) {
> - err = -ENOMEM;
> - goto out;
> - }
> + if (!vblk->vqs)
> + return -ENOMEM;
>
> names = kmalloc(sizeof(*names) * num_vqs, GFP_KERNEL);
> - if (!names)
> - goto err_names;
> -
> callbacks = kmalloc(sizeof(*callbacks) * num_vqs, GFP_KERNEL);
> - if (!callbacks)
> - goto err_callbacks;
> -
> vqs = kmalloc(sizeof(*vqs) * num_vqs, GFP_KERNEL);
> - if (!vqs)
> - goto err_vqs;
> + if (!names || !callbacks || !vqs) {
> + err = -ENOMEM;
> + goto out;
> + }
...you could use the
foo = kmalloc(...);
if (!foo)
goto out;
sequence in any case. This avoids trying again and again if e.g. the
names allocation already failed.
Alternatively, you should be fine if you don't init the variables to
NULL: The code is now either taking an early exit or setting all of the
variables anyway.
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