x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

3 files changed, 207 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/virtio/mmio.yaml b/Documentation/devicetree/bindings/virtio/mmio.yaml
new file mode 100644
index 000000000..0aa8433f0
--- /dev/null
+++ b/Documentation/devicetree/bindings/virtio/mmio.yaml
@@ -0,0 +1,67 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/virtio/mmio.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: virtio memory mapped devices
+
+maintainers:
+  - Jean-Philippe Brucker <jean-philippe@linaro.org>
+
+description:
+  See https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=virtio for
+  more details.
+
+properties:
+  compatible:
+    const: virtio,mmio
+
+  reg:
+    maxItems: 1
+
+  dma-coherent: true
+
+  interrupts:
+    maxItems: 1
+
+  '#iommu-cells':
+    description: Required when the node corresponds to a virtio-iommu device.
+    const: 1
+
+  iommus:
+    description: Required for devices making accesses thru an IOMMU.
+    maxItems: 1
+
+  wakeup-source:
+    type: boolean
+    description: Required for setting irq of a virtio_mmio device as wakeup source.
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+additionalProperties:
+  type: object
+
+examples:
+  - |
+    virtio@3000 {
+        compatible = "virtio,mmio";
+        reg = <0x3000 0x100>;
+        interrupts = <41>;
+
+        /* Device has endpoint ID 23 */
+        iommus = <&viommu 23>;
+    };
+
+    viommu: iommu@3100 {
+        compatible = "virtio,mmio";
+        reg = <0x3100 0x100>;
+        interrupts = <42>;
+
+        #iommu-cells = <1>;
+    };
+
+...
diff --git a/Documentation/devicetree/bindings/virtio/pci-iommu.yaml b/Documentation/devicetree/bindings/virtio/pci-iommu.yaml
new file mode 100644
index 000000000..8bd6ad72a
--- /dev/null
+++ b/Documentation/devicetree/bindings/virtio/pci-iommu.yaml
@@ -0,0 +1,99 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/virtio/pci-iommu.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: virtio-iommu device using the virtio-pci transport
+
+maintainers:
+  - Jean-Philippe Brucker <jean-philippe@linaro.org>
+
+description: |
+  When virtio-iommu uses the PCI transport, its programming interface is
+  discovered dynamically by the PCI probing infrastructure. However the
+  device tree statically describes the relation between IOMMU and DMA
+  masters. Therefore, the PCI root complex that hosts the virtio-iommu
+  contains a child node representing the IOMMU device explicitly.
+
+  DMA from the IOMMU device isn't managed by another IOMMU. Therefore the
+  virtio-iommu node doesn't have an "iommus" property, and is omitted from
+  the iommu-map property of the root complex.
+
+allOf:
+  - $ref: /schemas/pci/pci-device.yaml#
+
+properties:
+  # If compatible is present, it should contain the vendor and device ID
+  # according to the PCI Bus Binding specification. Since PCI provides
+  # built-in identification methods, compatible is not actually required.
+  compatible:
+    oneOf:
+      - items:
+          - const: virtio,pci-iommu
+          - const: pci1af4,1057
+      - items:
+          - const: pci1af4,1057
+
+  reg:
+    maxItems: 1
+
+  '#iommu-cells':
+    const: 1
+
+required:
+  - compatible
+  - reg
+  - '#iommu-cells'
+
+additionalProperties: false
+
+examples:
+  - |
+    bus {
+        #address-cells = <2>;
+        #size-cells = <2>;
+
+        pcie@40000000 {
+            device_type = "pci";
+            #address-cells = <3>;
+            #size-cells = <2>;
+            reg = <0x0 0x40000000  0x0 0x1000000>;
+            ranges = <0x02000000 0x0 0x41000000  0x0 0x41000000  0x0 0x0f000000>;
+
+            /*
+             * The IOMMU manages all functions in this PCI domain except
+             * itself. Omit BDF 00:01.0.
+             */
+            iommu-map = <0x0 &iommu0 0x0 0x8
+                         0x9 &iommu0 0x9 0xfff7>;
+
+            /* The IOMMU programming interface uses slot 00:01.0 */
+            iommu0: iommu@1,0 {
+                compatible = "pci1af4,1057";
+                reg = <0x800 0 0 0 0>;
+                #iommu-cells = <1>;
+            };
+        };
+
+        pcie@50000000 {
+            device_type = "pci";
+            #address-cells = <3>;
+            #size-cells = <2>;
+            reg = <0x0 0x50000000  0x0 0x1000000>;
+            ranges = <0x02000000 0x0 0x51000000  0x0 0x51000000  0x0 0x0f000000>;
+
+            /*
+             * The IOMMU also manages all functions from this domain,
+             * with endpoint IDs 0x10000 - 0x1ffff
+             */
+            iommu-map = <0x0 &iommu0 0x10000 0x10000>;
+        };
+
+        ethernet {
+            /* The IOMMU manages this platform device with endpoint ID 0x20000 */
+            iommus = <&iommu0 0x20000>;
+        };
+    };
+
+...
diff --git a/Documentation/devicetree/bindings/virtio/virtio-device.yaml b/Documentation/devicetree/bindings/virtio/virtio-device.yaml
new file mode 100644
index 000000000..8c6919ba9
--- /dev/null
+++ b/Documentation/devicetree/bindings/virtio/virtio-device.yaml
@@ -0,0 +1,41 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/virtio/virtio-device.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Virtio device
+
+maintainers:
+  - Viresh Kumar <viresh.kumar@linaro.org>
+
+description:
+  These bindings are applicable to virtio devices irrespective of the bus they
+  are bound to, like mmio or pci.
+
+# We need a select here so we don't match all nodes with 'virtio,mmio'
+properties:
+  compatible:
+    pattern: "^virtio,device[0-9a-f]{1,8}$"
+    description: Virtio device nodes.
+      "virtio,deviceID", where ID is the virtio device id. The textual
+      representation of ID shall be in lower case hexadecimal with leading
+      zeroes suppressed.
+
+required:
+  - compatible
+
+additionalProperties: true
+
+examples:
+  - |
+    virtio@3000 {
+        compatible = "virtio,mmio";
+        reg = <0x3000 0x100>;
+        interrupts = <43>;
+
+        i2c {
+            compatible = "virtio,device22";
+        };
+    };
+...