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 at cn.fujitsu.com>
Signed-off-by: Minfei Huang <minfei.hmf at alibaba-inc.com>
Signed-off-by: Minfei Huang <mnghuan at gmail.com>
---
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;
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;
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;
+ }
for (i = 0; i < num_vqs; i++) {
callbacks[i] = virtblk_done;
@@ -420,7 +414,7 @@ static int init_vq(struct virtio_blk *vblk)
/* Discover virtqueues and write information to configuration. */
err = vdev->config->find_vqs(vdev, num_vqs, vqs, callbacks, names);
if (err)
- goto err_find_vqs;
+ goto out;
for (i = 0; i < num_vqs; i++) {
spin_lock_init(&vblk->vqs[i].lock);
@@ -428,16 +422,12 @@ static int init_vq(struct virtio_blk *vblk)
}
vblk->num_vqs = num_vqs;
- err_find_vqs:
+out:
kfree(vqs);
- err_vqs:
kfree(callbacks);
- err_callbacks:
kfree(names);
- err_names:
if (err)
kfree(vblk->vqs);
- out:
return err;
}
--
2.7.4 (Apple Git-66)
On Mon, 18 Jul 2016 22:01:29 +0800 Minfei Huang <mnfhuang at gmail.com> 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 at cn.fujitsu.com> > Signed-off-by: Minfei Huang <minfei.hmf at alibaba-inc.com> > Signed-off-by: Minfei Huang <mnghuan at gmail.com> > --- > 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.
On 07/18/16 at 05:21P, Cornelia Huck wrote:> On Mon, 18 Jul 2016 22:01:29 +0800 > Minfei Huang <mnfhuang at gmail.com> wrote: > > 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...Hi, Cornelia. Thanks for reviewing this patch. Seems there is no need to init these variables to NULL. I will remove them laster.> > > 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.For this implementation, I have referred others which calls vdev->config->find_vqs as well. Yes, this continues trying to allocate memory, although memory allocation failed before.> > 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. >It's a big change if we refactor the helper ->find_vqs, since other devices also call it. Thanks Minfei