* [patch 1/2] vhost: potential integer overflows
@ 2010-10-11 17:22 Dan Carpenter
2010-10-11 17:26 ` Al Viro
2010-10-12 12:25 ` Michael S. Tsirkin
0 siblings, 2 replies; 4+ messages in thread
From: Dan Carpenter @ 2010-10-11 17:22 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Juan Quintela, David S. Miller, Rusty Russell, kvm,
virtualization, netdev, kernel-janitors
I did an audit for potential integer overflows of values which get passed
to access_ok() and here are the results.
Signed-off-by: Dan Carpenter <error27@gmail.com>
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index dd3d6f7..c2aa12c 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -429,6 +429,14 @@ static int vq_access_ok(unsigned int num,
struct vring_avail __user *avail,
struct vring_used __user *used)
{
+
+ if (num > UINT_MAX / sizeof *desc)
+ return 0;
+ if (num > UINT_MAX / sizeof *avail->ring - sizeof *avail)
+ return 0;
+ if (num > UINT_MAX / sizeof *used->ring - sizeof *used)
+ return 0;
+
return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
access_ok(VERIFY_READ, avail,
sizeof *avail + num * sizeof *avail->ring) &&
@@ -447,6 +455,9 @@ int vhost_log_access_ok(struct vhost_dev *dev)
/* Caller should have vq mutex and device mutex */
static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
{
+ if (vq->num > UINT_MAX / sizeof *vq->used->ring - sizeof *vq->used)
+ return 0;
+
return vq_memory_access_ok(log_base, vq->dev->memory,
vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
(!vq->log_used || log_access_ok(log_base, vq->log_addr,
@@ -606,12 +617,17 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
}
/* Also validate log access for used ring if enabled. */
- if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
- !log_access_ok(vq->log_base, a.log_guest_addr,
+ if (a.flags & (0x1 << VHOST_VRING_F_LOG)) {
+ if (vq->num > UINT_MAX / sizeof *vq->used->ring - sizeof *vq->used) {
+ r = -EINVAL;
+ break;
+ }
+ if (!log_access_ok(vq->log_base, a.log_guest_addr,
sizeof *vq->used +
vq->num * sizeof *vq->used->ring)) {
- r = -EINVAL;
- break;
+ r = -EINVAL;
+ break;
+ }
}
}
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [patch 1/2] vhost: potential integer overflows
2010-10-11 17:22 [patch 1/2] vhost: potential integer overflows Dan Carpenter
@ 2010-10-11 17:26 ` Al Viro
2010-10-12 12:25 ` Michael S. Tsirkin
1 sibling, 0 replies; 4+ messages in thread
From: Al Viro @ 2010-10-11 17:26 UTC (permalink / raw)
To: Dan Carpenter
Cc: Michael S. Tsirkin, Juan Quintela, David S. Miller, Rusty Russell,
kvm, virtualization, netdev, kernel-janitors
On Mon, Oct 11, 2010 at 07:22:57PM +0200, Dan Carpenter wrote:
> I did an audit for potential integer overflows of values which get passed
> to access_ok() and here are the results.
FWIW, UINT_MAX is wrong here. What you want is maximal size_t value.
> Signed-off-by: Dan Carpenter <error27@gmail.com>
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index dd3d6f7..c2aa12c 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -429,6 +429,14 @@ static int vq_access_ok(unsigned int num,
> struct vring_avail __user *avail,
> struct vring_used __user *used)
> {
> +
> + if (num > UINT_MAX / sizeof *desc)
> + return 0;
> + if (num > UINT_MAX / sizeof *avail->ring - sizeof *avail)
> + return 0;
> + if (num > UINT_MAX / sizeof *used->ring - sizeof *used)
> + return 0;
> +
> return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
> access_ok(VERIFY_READ, avail,
> sizeof *avail + num * sizeof *avail->ring) &&
> @@ -447,6 +455,9 @@ int vhost_log_access_ok(struct vhost_dev *dev)
> /* Caller should have vq mutex and device mutex */
> static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
> {
> + if (vq->num > UINT_MAX / sizeof *vq->used->ring - sizeof *vq->used)
> + return 0;
> +
> return vq_memory_access_ok(log_base, vq->dev->memory,
> vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
> (!vq->log_used || log_access_ok(log_base, vq->log_addr,
> @@ -606,12 +617,17 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
> }
>
> /* Also validate log access for used ring if enabled. */
> - if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
> - !log_access_ok(vq->log_base, a.log_guest_addr,
> + if (a.flags & (0x1 << VHOST_VRING_F_LOG)) {
> + if (vq->num > UINT_MAX / sizeof *vq->used->ring - sizeof *vq->used) {
> + r = -EINVAL;
> + break;
> + }
> + if (!log_access_ok(vq->log_base, a.log_guest_addr,
> sizeof *vq->used +
> vq->num * sizeof *vq->used->ring)) {
> - r = -EINVAL;
> - break;
> + r = -EINVAL;
> + break;
> + }
> }
> }
>
> --
> To unsubscribe from this list: send the line "unsubscribe netdev" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [patch 1/2] vhost: potential integer overflows
2010-10-11 17:22 [patch 1/2] vhost: potential integer overflows Dan Carpenter
2010-10-11 17:26 ` Al Viro
@ 2010-10-12 12:25 ` Michael S. Tsirkin
2010-10-12 14:51 ` Dan Carpenter
1 sibling, 1 reply; 4+ messages in thread
From: Michael S. Tsirkin @ 2010-10-12 12:25 UTC (permalink / raw)
To: Dan Carpenter
Cc: Juan Quintela, David S. Miller, Rusty Russell, kvm,
virtualization, netdev, kernel-janitors
On Mon, Oct 11, 2010 at 07:22:57PM +0200, Dan Carpenter wrote:
> I did an audit for potential integer overflows of values which get passed
> to access_ok() and here are the results.
>
> Signed-off-by: Dan Carpenter <error27@gmail.com>
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index dd3d6f7..c2aa12c 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -429,6 +429,14 @@ static int vq_access_ok(unsigned int num,
> struct vring_avail __user *avail,
> struct vring_used __user *used)
> {
> +
> + if (num > UINT_MAX / sizeof *desc)
> + return 0;
> + if (num > UINT_MAX / sizeof *avail->ring - sizeof *avail)
> + return 0;
> + if (num > UINT_MAX / sizeof *used->ring - sizeof *used)
> + return 0;
> +
> return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
> access_ok(VERIFY_READ, avail,
> sizeof *avail + num * sizeof *avail->ring) &&
> @@ -447,6 +455,9 @@ int vhost_log_access_ok(struct vhost_dev *dev)
> /* Caller should have vq mutex and device mutex */
> static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
> {
> + if (vq->num > UINT_MAX / sizeof *vq->used->ring - sizeof *vq->used)
> + return 0;
> +
> return vq_memory_access_ok(log_base, vq->dev->memory,
> vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
> (!vq->log_used || log_access_ok(log_base, vq->log_addr,
> @@ -606,12 +617,17 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
> }
>
> /* Also validate log access for used ring if enabled. */
> - if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
> - !log_access_ok(vq->log_base, a.log_guest_addr,
> + if (a.flags & (0x1 << VHOST_VRING_F_LOG)) {
> + if (vq->num > UINT_MAX / sizeof *vq->used->ring - sizeof *vq->used) {
> + r = -EINVAL;
> + break;
> + }
> + if (!log_access_ok(vq->log_base, a.log_guest_addr,
> sizeof *vq->used +
> vq->num * sizeof *vq->used->ring)) {
> - r = -EINVAL;
> - break;
> + r = -EINVAL;
> + break;
> + }
> }
> }
>
As far as I can see, maximum value for num is 64K - 1:
if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
r = -EINVAL;
break;
}
How can any of the above two trigger?
It seems easier to check value for sanity at a single place where it's
passed from userspace to kernel.
--
MST
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [patch 1/2] vhost: potential integer overflows
2010-10-12 12:25 ` Michael S. Tsirkin
@ 2010-10-12 14:51 ` Dan Carpenter
0 siblings, 0 replies; 4+ messages in thread
From: Dan Carpenter @ 2010-10-12 14:51 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Juan Quintela, David S. Miller, Rusty Russell, kvm,
virtualization, netdev, kernel-janitors
On Tue, Oct 12, 2010 at 02:25:48PM +0200, Michael S. Tsirkin wrote:
>
> As far as I can see, maximum value for num is 64K - 1:
>
> if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
> r = -EINVAL;
> break;
> }
>
> How can any of the above two trigger?
> It seems easier to check value for sanity at a single place where it's
> passed from userspace to kernel.
>
Gar. Sorry for that. My mistake.
regards,
dan carpenter
^ permalink raw reply [flat|nested] 4+ messages in thread
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2010-10-11 17:22 [patch 1/2] vhost: potential integer overflows Dan Carpenter
2010-10-11 17:26 ` Al Viro
2010-10-12 12:25 ` Michael S. Tsirkin
2010-10-12 14:51 ` Dan Carpenter
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