when kmalloc() fails in kvm_io_bus_unregister_dev(), before removing
the bus, we should iterate over all other devices linked to it and call
kvm_iodevice_destructor() for them
Reported-and-tested-by: [email protected]
Link: https://syzkaller.appspot.com/bug?extid=f196caa45793d6374707
Signed-off-by: Rustam Kovhaev <[email protected]>
Reviewed-by: Vitaly Kuznetsov <[email protected]>
---
v2:
- remove redundant whitespace
- remove goto statement and use if/else
---
virt/kvm/kvm_main.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 67cd0b88a6b6..cf88233b819a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4332,7 +4332,7 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
struct kvm_io_device *dev)
{
- int i;
+ int i, j;
struct kvm_io_bus *new_bus, *bus;
bus = kvm_get_bus(kvm, bus_idx);
@@ -4349,17 +4349,20 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1),
GFP_KERNEL_ACCOUNT);
- if (!new_bus) {
+ if (new_bus) {
+ memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
+ new_bus->dev_count--;
+ memcpy(new_bus->range + i, bus->range + i + 1,
+ (new_bus->dev_count - i) * sizeof(struct kvm_io_range));
+ } else {
pr_err("kvm: failed to shrink bus, removing it completely\n");
- goto broken;
+ for (j = 0; j < bus->dev_count; j++) {
+ if (j == i)
+ continue;
+ kvm_iodevice_destructor(bus->range[j].dev);
+ }
}
- memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
- new_bus->dev_count--;
- memcpy(new_bus->range + i, bus->range + i + 1,
- (new_bus->dev_count - i) * sizeof(struct kvm_io_range));
-
-broken:
rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
synchronize_srcu_expedited(&kvm->srcu);
kfree(bus);
--
2.28.0
Hi,
On 9/2/20 17:57, Rustam Kovhaev wrote:
> when kmalloc() fails in kvm_io_bus_unregister_dev(), before removing
> the bus, we should iterate over all other devices linked to it and call
> kvm_iodevice_destructor() for them
>
> Reported-and-tested-by: [email protected]
> Link: https://syzkaller.appspot.com/bug?extid=f196caa45793d6374707
> Signed-off-by: Rustam Kovhaev <[email protected]>
> Reviewed-by: Vitaly Kuznetsov <[email protected]>
I think it's worthwhile to add a Fixes tag for this, too.
Please, see more comments below...
> ---
> v2:
> - remove redundant whitespace
> - remove goto statement and use if/else
> ---
> virt/kvm/kvm_main.c | 21 ++++++++++++---------
> 1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 67cd0b88a6b6..cf88233b819a 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4332,7 +4332,7 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
> void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
> struct kvm_io_device *dev)
> {
> - int i;
> + int i, j;
> struct kvm_io_bus *new_bus, *bus;
>
> bus = kvm_get_bus(kvm, bus_idx);
> @@ -4349,17 +4349,20 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
>
> new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1),
> GFP_KERNEL_ACCOUNT);
> - if (!new_bus) {
> + if (new_bus) {
> + memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
^^^
It seems that you can use struct_size() here (see the allocation code above)...
> + new_bus->dev_count--;
> + memcpy(new_bus->range + i, bus->range + i + 1,
> + (new_bus->dev_count - i) * sizeof(struct kvm_io_range));
^^^
...and, if possible, you can also use flex_array_size() here.
Thanks
--
Gustavo
> + } else {
> pr_err("kvm: failed to shrink bus, removing it completely\n");
> - goto broken;
> + for (j = 0; j < bus->dev_count; j++) {
> + if (j == i)
> + continue;
> + kvm_iodevice_destructor(bus->range[j].dev);
> + }
> }
>
> - memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
> - new_bus->dev_count--;
> - memcpy(new_bus->range + i, bus->range + i + 1,
> - (new_bus->dev_count - i) * sizeof(struct kvm_io_range));
> -
> -broken:
> rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
> synchronize_srcu_expedited(&kvm->srcu);
> kfree(bus);
>
On Wed, Sep 02, 2020 at 06:34:11PM -0500, Gustavo A. R. Silva wrote:
> Hi,
>
> On 9/2/20 17:57, Rustam Kovhaev wrote:
> > when kmalloc() fails in kvm_io_bus_unregister_dev(), before removing
> > the bus, we should iterate over all other devices linked to it and call
> > kvm_iodevice_destructor() for them
> >
> > Reported-and-tested-by: [email protected]
> > Link: https://syzkaller.appspot.com/bug?extid=f196caa45793d6374707
> > Signed-off-by: Rustam Kovhaev <[email protected]>
> > Reviewed-by: Vitaly Kuznetsov <[email protected]>
>
> I think it's worthwhile to add a Fixes tag for this, too.
>
> Please, see more comments below...
>
> > ---
> > v2:
> > - remove redundant whitespace
> > - remove goto statement and use if/else
> > ---
> > virt/kvm/kvm_main.c | 21 ++++++++++++---------
> > 1 file changed, 12 insertions(+), 9 deletions(-)
> >
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index 67cd0b88a6b6..cf88233b819a 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -4332,7 +4332,7 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
> > void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
> > struct kvm_io_device *dev)
> > {
> > - int i;
> > + int i, j;
> > struct kvm_io_bus *new_bus, *bus;
> >
> > bus = kvm_get_bus(kvm, bus_idx);
> > @@ -4349,17 +4349,20 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
> >
> > new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1),
> > GFP_KERNEL_ACCOUNT);
> > - if (!new_bus) {
> > + if (new_bus) {
> > + memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
>
> ^^^
> It seems that you can use struct_size() here (see the allocation code above)...
>
> > + new_bus->dev_count--;
> > + memcpy(new_bus->range + i, bus->range + i + 1,
> > + (new_bus->dev_count - i) * sizeof(struct kvm_io_range));
>
> ^^^
> ...and, if possible, you can also use flex_array_size() here.
>
> Thanks
> --
> Gustavo
>
> > + } else {
> > pr_err("kvm: failed to shrink bus, removing it completely\n");
> > - goto broken;
> > + for (j = 0; j < bus->dev_count; j++) {
> > + if (j == i)
> > + continue;
> > + kvm_iodevice_destructor(bus->range[j].dev);
> > + }
> > }
> >
> > - memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
> > - new_bus->dev_count--;
> > - memcpy(new_bus->range + i, bus->range + i + 1,
> > - (new_bus->dev_count - i) * sizeof(struct kvm_io_range));
> > -
> > -broken:
> > rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
> > synchronize_srcu_expedited(&kvm->srcu);
> > kfree(bus);
> >
hi Gustavo, thank you for the review, i'll send the new patch.
Vitaly, i think i will need to drop your "Reviewed-by", because there is
going to be a bit more changes
Rustam Kovhaev <[email protected]> writes:
> On Wed, Sep 02, 2020 at 06:34:11PM -0500, Gustavo A. R. Silva wrote:
>> Hi,
>>
>> On 9/2/20 17:57, Rustam Kovhaev wrote:
>> > when kmalloc() fails in kvm_io_bus_unregister_dev(), before removing
>> > the bus, we should iterate over all other devices linked to it and call
>> > kvm_iodevice_destructor() for them
>> >
>> > Reported-and-tested-by: [email protected]
>> > Link: https://syzkaller.appspot.com/bug?extid=f196caa45793d6374707
>> > Signed-off-by: Rustam Kovhaev <[email protected]>
>> > Reviewed-by: Vitaly Kuznetsov <[email protected]>
>>
>> I think it's worthwhile to add a Fixes tag for this, too.
>>
>> Please, see more comments below...
>>
>> > ---
>> > v2:
>> > - remove redundant whitespace
>> > - remove goto statement and use if/else
>> > ---
>> > virt/kvm/kvm_main.c | 21 ++++++++++++---------
>> > 1 file changed, 12 insertions(+), 9 deletions(-)
>> >
>> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>> > index 67cd0b88a6b6..cf88233b819a 100644
>> > --- a/virt/kvm/kvm_main.c
>> > +++ b/virt/kvm/kvm_main.c
>> > @@ -4332,7 +4332,7 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
>> > void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
>> > struct kvm_io_device *dev)
>> > {
>> > - int i;
>> > + int i, j;
>> > struct kvm_io_bus *new_bus, *bus;
>> >
>> > bus = kvm_get_bus(kvm, bus_idx);
>> > @@ -4349,17 +4349,20 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
>> >
>> > new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1),
>> > GFP_KERNEL_ACCOUNT);
>> > - if (!new_bus) {
>> > + if (new_bus) {
>> > + memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
>>
>> ^^^
>> It seems that you can use struct_size() here (see the allocation code above)...
>>
>> > + new_bus->dev_count--;
>> > + memcpy(new_bus->range + i, bus->range + i + 1,
>> > + (new_bus->dev_count - i) * sizeof(struct kvm_io_range));
>>
>> ^^^
>> ...and, if possible, you can also use flex_array_size() here.
>>
>> Thanks
>> --
>> Gustavo
>>
>> > + } else {
>> > pr_err("kvm: failed to shrink bus, removing it completely\n");
>> > - goto broken;
>> > + for (j = 0; j < bus->dev_count; j++) {
>> > + if (j == i)
>> > + continue;
>> > + kvm_iodevice_destructor(bus->range[j].dev);
>> > + }
>> > }
>> >
>> > - memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
>> > - new_bus->dev_count--;
>> > - memcpy(new_bus->range + i, bus->range + i + 1,
>> > - (new_bus->dev_count - i) * sizeof(struct kvm_io_range));
>> > -
>> > -broken:
>> > rcu_assign_pointer(kvm->buses[bus_idx], new_bus);
>> > synchronize_srcu_expedited(&kvm->srcu);
>> > kfree(bus);
>> >
>
> hi Gustavo, thank you for the review, i'll send the new patch.
> Vitaly, i think i will need to drop your "Reviewed-by", because there is
> going to be a bit more changes
>
Personally, I'd prefer to make struct_size()/flex_array_size() a
separate preparatory patch so the real fix is small but I don't have a
strong opinion. I'll take look at v3 so feel free to drop R-b if you
decide to make a combined patch and feel free to keep it if you make the
preparatory changes separate :-)
--
Vitaly
On Fri, Sep 04, 2020 at 02:04:23PM +0200, Vitaly Kuznetsov wrote:
> Rustam Kovhaev <[email protected]> writes:
>
> > On Wed, Sep 02, 2020 at 06:34:11PM -0500, Gustavo A. R. Silva wrote:
> >> Hi,
> >>
> >> On 9/2/20 17:57, Rustam Kovhaev wrote:
> >> > when kmalloc() fails in kvm_io_bus_unregister_dev(), before removing
> >> > the bus, we should iterate over all other devices linked to it and call
> >> > kvm_iodevice_destructor() for them
> >> >
> >> > Reported-and-tested-by: [email protected]
> >> > Link: https://syzkaller.appspot.com/bug?extid=f196caa45793d6374707
> >> > Signed-off-by: Rustam Kovhaev <[email protected]>
> >> > Reviewed-by: Vitaly Kuznetsov <[email protected]>
> >>
> >> I think it's worthwhile to add a Fixes tag for this, too.
> >>
> >> Please, see more comments below...
[..]
> >
> > hi Gustavo, thank you for the review, i'll send the new patch.
> > Vitaly, i think i will need to drop your "Reviewed-by", because there is
> > going to be a bit more changes
> >
>
> Personally, I'd prefer to make struct_size()/flex_array_size() a
> separate preparatory patch so the real fix is small but I don't have a
> strong opinion. I'll take look at v3 so feel free to drop R-b if you
> decide to make a combined patch and feel free to keep it if you make the
> preparatory changes separate :-)
>
I agree. A two-patch series is much better in this case.
Rustam - please add a Fixes tag to the first patch and see if it can be
applied to -stable. If so, you should Cc [email protected], too.
Thanks
--
Gustavo