| Message ID | d9c3a564af9e2c5bf63f48a7dcbf08cd593c5c0b.1665802985.git.renzhengeek@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [V2] KVM: arm64: vgic: fix wrong loop condition in scan_its_table() | expand |
On Sat, 15 Oct 2022 11:19:28 +0800, 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 \ > ... > > [...] Applied to fixes, thanks! [1/1] KVM: arm64: vgic: fix wrong loop condition in scan_its_table() commit: c000a2607145d28b06c697f968491372ea56c23a Cheers, M.
diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c index 24d7778..733b530 100644 --- a/arch/arm64/kvm/vgic/vgic-its.c +++ b/arch/arm64/kvm/vgic/vgic-its.c @@ -2149,7 +2149,7 @@ static int scan_its_table(struct vgic_its *its, gpa_t base, int size, u32 esz, memset(entry, 0, esz); - while (len > 0) { + while (true) { int next_offset; size_t byte_offset; @@ -2162,6 +2162,9 @@ static int scan_its_table(struct vgic_its *its, gpa_t base, int size, u32 esz, return next_offset; byte_offset = next_offset * esz; + if (byte_offset >= len) + break; + id += next_offset; gpa += byte_offset; len -= byte_offset;
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; 3. vgic its use 2 level device table. 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 with a bad GPA. For example, 1. L1 table has 2 entries; 2. and we are now scanning at L2 table entry index 2075 (pointed by L1 first entry) 3. if next device id is 9472, we will get a big offset: 7397; 4. with signed 'len', 'len -= offset * esz', len will underflow to a positive number, mistakenly into next iteration with a bad GPA; (It should break the current L2 table scanning, and jump into the next L1 table entry) 5. that bad GPA fails the guest read. Fix it by stopping the L2 table scan when the next device id fits into next L1 table entry. Thanks Eric Auger's suggestion for the fix. Fixes: 920a7a8fa92a ("KVM: arm64: vgic-its: Add infrastructure for tableookup") Signed-off-by: Eric Ren <renzhengeek@gmail.com> --- arch/arm64/kvm/vgic/vgic-its.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)