Rustam Kovhaev <rkovhaev@xxxxxxxxx> 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: syzbot+f196caa45793d6374707@xxxxxxxxxxxxxxxxxxxxxxxxx >> > Link: https://syzkaller.appspot.com/bug?extid=f196caa45793d6374707 >> > Signed-off-by: Rustam Kovhaev <rkovhaev@xxxxxxxxx> >> > Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> >> >> 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
