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

1 files changed, 272 insertions, 0 deletions

diff --git a/drivers/iommu/amd/ppr.c b/drivers/iommu/amd/ppr.c
new file mode 100644
index 000000000..2039a9dd7
--- /dev/null
+++ b/drivers/iommu/amd/ppr.c
@@ -0,0 +1,272 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2023 Advanced Micro Devices, Inc.
+ */
+
+#define pr_fmt(fmt)     "AMD-Vi: " fmt
+#define dev_fmt(fmt)    pr_fmt(fmt)
+
+#include <linux/amd-iommu.h>
+#include <linux/delay.h>
+#include <linux/mmu_notifier.h>
+
+#include <asm/iommu.h>
+
+#include "amd_iommu.h"
+#include "amd_iommu_types.h"
+
+#include "../iommu-pages.h"
+
+int __init amd_iommu_alloc_ppr_log(struct amd_iommu *iommu)
+{
+	iommu->ppr_log = iommu_alloc_4k_pages(iommu, GFP_KERNEL | __GFP_ZERO,
+					      amd_iommu_pprlog_size);
+	return iommu->ppr_log ? 0 : -ENOMEM;
+}
+
+void amd_iommu_enable_ppr_log(struct amd_iommu *iommu)
+{
+	u64 entry;
+
+	if (iommu->ppr_log == NULL)
+		return;
+
+	iommu_feature_enable(iommu, CONTROL_PPR_EN);
+
+	entry = iommu_virt_to_phys(iommu->ppr_log);
+	entry |= (amd_iommu_pprlog_size == PPRLOG_SIZE_DEF) ?
+			PPRLOG_LEN_MASK_DEF : PPRLOG_LEN_MASK_MAX;
+
+	memcpy_toio(iommu->mmio_base + MMIO_PPR_LOG_OFFSET,
+		    &entry, sizeof(entry));
+
+	/* set head and tail to zero manually */
+	writel(0x00, iommu->mmio_base + MMIO_PPR_HEAD_OFFSET);
+	writel(0x00, iommu->mmio_base + MMIO_PPR_TAIL_OFFSET);
+
+	iommu_feature_enable(iommu, CONTROL_PPRINT_EN);
+	iommu_feature_enable(iommu, CONTROL_PPRLOG_EN);
+}
+
+void __init amd_iommu_free_ppr_log(struct amd_iommu *iommu)
+{
+	iommu_free_pages(iommu->ppr_log);
+}
+
+/*
+ * This function restarts ppr logging in case the IOMMU experienced
+ * PPR log overflow.
+ */
+void amd_iommu_restart_ppr_log(struct amd_iommu *iommu)
+{
+	amd_iommu_restart_log(iommu, "PPR", CONTROL_PPRINT_EN,
+			      CONTROL_PPRLOG_EN, MMIO_STATUS_PPR_RUN_MASK,
+			      MMIO_STATUS_PPR_OVERFLOW_MASK);
+}
+
+static inline u32 ppr_flag_to_fault_perm(u16 flag)
+{
+	int perm = 0;
+
+	if (flag & PPR_FLAG_READ)
+		perm |= IOMMU_FAULT_PERM_READ;
+	if (flag & PPR_FLAG_WRITE)
+		perm |= IOMMU_FAULT_PERM_WRITE;
+	if (flag & PPR_FLAG_EXEC)
+		perm |= IOMMU_FAULT_PERM_EXEC;
+	if (!(flag & PPR_FLAG_US))
+		perm |= IOMMU_FAULT_PERM_PRIV;
+
+	return perm;
+}
+
+static bool ppr_is_valid(struct amd_iommu *iommu, u64 *raw)
+{
+	struct device *dev = iommu->iommu.dev;
+	u16 devid = PPR_DEVID(raw[0]);
+
+	if (!(PPR_FLAGS(raw[0]) & PPR_FLAG_GN)) {
+		dev_dbg(dev, "PPR logged [Request ignored due to GN=0 (device=%04x:%02x:%02x.%x "
+			"pasid=0x%05llx address=0x%llx flags=0x%04llx tag=0x%03llx]\n",
+			iommu->pci_seg->id, PCI_BUS_NUM(devid), PCI_SLOT(devid), PCI_FUNC(devid),
+			PPR_PASID(raw[0]), raw[1], PPR_FLAGS(raw[0]), PPR_TAG(raw[0]));
+		return false;
+	}
+
+	if (PPR_FLAGS(raw[0]) & PPR_FLAG_RVSD) {
+		dev_dbg(dev, "PPR logged [Invalid request format (device=%04x:%02x:%02x.%x "
+			"pasid=0x%05llx address=0x%llx flags=0x%04llx tag=0x%03llx]\n",
+			iommu->pci_seg->id, PCI_BUS_NUM(devid), PCI_SLOT(devid), PCI_FUNC(devid),
+			PPR_PASID(raw[0]), raw[1], PPR_FLAGS(raw[0]), PPR_TAG(raw[0]));
+		return false;
+	}
+
+	return true;
+}
+
+static void iommu_call_iopf_notifier(struct amd_iommu *iommu, u64 *raw)
+{
+	struct iommu_dev_data *dev_data;
+	struct iopf_fault event;
+	struct pci_dev *pdev;
+	u16 devid = PPR_DEVID(raw[0]);
+
+	if (PPR_REQ_TYPE(raw[0]) != PPR_REQ_FAULT) {
+		pr_info_ratelimited("Unknown PPR request received\n");
+		return;
+	}
+
+	pdev = pci_get_domain_bus_and_slot(iommu->pci_seg->id,
+					   PCI_BUS_NUM(devid), devid & 0xff);
+	if (!pdev)
+		return;
+
+	if (!ppr_is_valid(iommu, raw))
+		goto out;
+
+	memset(&event, 0, sizeof(struct iopf_fault));
+
+	event.fault.type = IOMMU_FAULT_PAGE_REQ;
+	event.fault.prm.perm = ppr_flag_to_fault_perm(PPR_FLAGS(raw[0]));
+	event.fault.prm.addr = (u64)(raw[1] & PAGE_MASK);
+	event.fault.prm.pasid = PPR_PASID(raw[0]);
+	event.fault.prm.grpid = PPR_TAG(raw[0]);
+
+	/*
+	 * PASID zero is used for requests from the I/O device without
+	 * a PASID
+	 */
+	dev_data = dev_iommu_priv_get(&pdev->dev);
+	if (event.fault.prm.pasid == 0 ||
+	    event.fault.prm.pasid >= dev_data->max_pasids) {
+		pr_info_ratelimited("Invalid PASID : 0x%x, device : 0x%x\n",
+				    event.fault.prm.pasid, dev_data->devid);
+		goto out;
+	}
+
+	event.fault.prm.flags |= IOMMU_FAULT_PAGE_RESPONSE_NEEDS_PASID;
+	event.fault.prm.flags |= IOMMU_FAULT_PAGE_REQUEST_PASID_VALID;
+	if (PPR_TAG_LAST_PAGE(raw[0]))
+		event.fault.prm.flags |= IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE;
+
+	/* Submit event */
+	iommu_report_device_fault(&pdev->dev, &event);
+	pci_dev_put(pdev);
+	return;
+
+out:
+	/* Nobody cared, abort */
+	amd_iommu_complete_ppr(&pdev->dev, PPR_PASID(raw[0]),
+			       IOMMU_PAGE_RESP_FAILURE, PPR_TAG(raw[0]));
+	pci_dev_put(pdev);
+}
+
+void amd_iommu_poll_ppr_log(struct amd_iommu *iommu)
+{
+	u32 head, tail;
+
+	head = readl(iommu->mmio_base + MMIO_PPR_HEAD_OFFSET);
+	tail = readl(iommu->mmio_base + MMIO_PPR_TAIL_OFFSET);
+
+	while (head != tail) {
+		volatile u64 *raw;
+		u64 entry[2];
+		int i;
+
+		raw = (u64 *)(iommu->ppr_log + head);
+
+		/*
+		 * Hardware bug: Interrupt may arrive before the entry is
+		 * written to memory. If this happens we need to wait for the
+		 * entry to arrive.
+		 */
+		for (i = 0; i < LOOP_TIMEOUT; ++i) {
+			if (PPR_REQ_TYPE(raw[0]) != 0)
+				break;
+			udelay(1);
+		}
+
+		/* Avoid memcpy function-call overhead */
+		entry[0] = raw[0];
+		entry[1] = raw[1];
+
+		/*
+		 * To detect the hardware errata 733 we need to clear the
+		 * entry back to zero. This issue does not exist on SNP
+		 * enabled system. Also this buffer is not writeable on
+		 * SNP enabled system.
+		 */
+		if (!amd_iommu_snp_en)
+			raw[0] = raw[1] = 0UL;
+
+		/* Update head pointer of hardware ring-buffer */
+		head = (head + PPRLOG_ENTRY_SIZE) % amd_iommu_pprlog_size;
+		writel(head, iommu->mmio_base + MMIO_PPR_HEAD_OFFSET);
+
+		/* Handle PPR entry */
+		iommu_call_iopf_notifier(iommu, entry);
+	}
+}
+
+/**************************************************************
+ *
+ * IOPF handling stuff
+ */
+
+/* Setup per-IOMMU IOPF queue if not exist. */
+int amd_iommu_iopf_init(struct amd_iommu *iommu)
+{
+	int ret = 0;
+
+	if (iommu->iopf_queue)
+		return ret;
+
+	snprintf(iommu->iopfq_name, sizeof(iommu->iopfq_name), "amdvi-%#x",
+		 PCI_SEG_DEVID_TO_SBDF(iommu->pci_seg->id, iommu->devid));
+
+	iommu->iopf_queue = iopf_queue_alloc(iommu->iopfq_name);
+	if (!iommu->iopf_queue)
+		ret = -ENOMEM;
+
+	return ret;
+}
+
+/* Destroy per-IOMMU IOPF queue if no longer needed. */
+void amd_iommu_iopf_uninit(struct amd_iommu *iommu)
+{
+	iopf_queue_free(iommu->iopf_queue);
+	iommu->iopf_queue = NULL;
+}
+
+void amd_iommu_page_response(struct device *dev, struct iopf_fault *evt,
+			     struct iommu_page_response *resp)
+{
+	amd_iommu_complete_ppr(dev, resp->pasid, resp->code, resp->grpid);
+}
+
+int amd_iommu_iopf_add_device(struct amd_iommu *iommu,
+			      struct iommu_dev_data *dev_data)
+{
+	int ret = 0;
+
+	if (!dev_data->pri_enabled)
+		return ret;
+
+	if (!iommu->iopf_queue)
+		return -EINVAL;
+
+	ret = iopf_queue_add_device(iommu->iopf_queue, dev_data->dev);
+	if (ret)
+		return ret;
+
+	dev_data->ppr = true;
+	return 0;
+}
+
+/* Its assumed that caller has verified that device was added to iopf queue */
+void amd_iommu_iopf_remove_device(struct amd_iommu *iommu,
+				  struct iommu_dev_data *dev_data)
+{
+	iopf_queue_remove_device(iommu->iopf_queue, dev_data->dev);
+	dev_data->ppr = false;
+}