Hi,
On 10/12/22 18:59, Eric Ren wrote:
> Reproducer hints:
> 1. Create ARM virt VM with pxb-pcie bus which adds
> extra host bridges, with qemu command like:
>
> ```
> -device pxb-pcie,bus_nr=8,id=pci.x,numa_node=0,bus=pcie.0 \
> -device pcie-root-port,..,bus=pci.x \
> ...
> -device pxb-pcie,bus_nr=37,id=pci.y,numa_node=1,bus=pcie.0 \
> -device pcie-root-port,..,bus=pci.y \
> ...
>
> ```
> 2. Perform VM migration which calls save/restore device tables.
>
> In that setup, we get a big "offset" between 2 device_ids (
> one is small, another is big), which makes unsigned "len" round
> up a big positive number, causing loop to continue exceptionally.
>
> Signed-off-by: Eric Ren <renzhengeek@xxxxxxxxx>
I fixed Marc's address and removed Christoffer's one. Please use the
scripts/get_maintainer.pl to identify the right email addresses.
Just to make sure I correctly understand, you mean len -= byte_offset
becomes negative and that is not properly reflected due to the unsigned
type. I agree we should be robust against that but doesn't it also mean
that the saved table has an issue in the first place (the offset points
to a location outside of the max size of the table)?
Thanks
Eric
> ---
> arch/arm64/kvm/vgic/vgic-its.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
> index 24d7778d1ce6..673554ef02f9 100644
> --- a/arch/arm64/kvm/vgic/vgic-its.c
> +++ b/arch/arm64/kvm/vgic/vgic-its.c
> @@ -2141,7 +2141,7 @@ static int scan_its_table(struct vgic_its *its, gpa_t base, int size, u32 esz,
> int start_id, entry_fn_t fn, void *opaque)
> {
> struct kvm *kvm = its->dev->kvm;
> - unsigned long len = size;
> + ssize_t len = size;
> int id = start_id;
> gpa_t gpa = base;
> char entry[ESZ_MAX];
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