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, 396 insertions, 0 deletions

diff --git a/drivers/iommu/intel/prq.c b/drivers/iommu/intel/prq.c
new file mode 100644
index 000000000..dddd3b51b
--- /dev/null
+++ b/drivers/iommu/intel/prq.c
@@ -0,0 +1,396 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2015 Intel Corporation
+ *
+ * Originally split from drivers/iommu/intel/svm.c
+ */
+
+#include <linux/pci.h>
+#include <linux/pci-ats.h>
+
+#include "iommu.h"
+#include "pasid.h"
+#include "../iommu-pages.h"
+#include "trace.h"
+
+/* Page request queue descriptor */
+struct page_req_dsc {
+	union {
+		struct {
+			u64 type:8;
+			u64 pasid_present:1;
+			u64 rsvd:7;
+			u64 rid:16;
+			u64 pasid:20;
+			u64 exe_req:1;
+			u64 pm_req:1;
+			u64 rsvd2:10;
+		};
+		u64 qw_0;
+	};
+	union {
+		struct {
+			u64 rd_req:1;
+			u64 wr_req:1;
+			u64 lpig:1;
+			u64 prg_index:9;
+			u64 addr:52;
+		};
+		u64 qw_1;
+	};
+	u64 qw_2;
+	u64 qw_3;
+};
+
+/**
+ * intel_iommu_drain_pasid_prq - Drain page requests and responses for a pasid
+ * @dev: target device
+ * @pasid: pasid for draining
+ *
+ * Drain all pending page requests and responses related to @pasid in both
+ * software and hardware. This is supposed to be called after the device
+ * driver has stopped DMA, the pasid entry has been cleared, and both IOTLB
+ * and DevTLB have been invalidated.
+ *
+ * It waits until all pending page requests for @pasid in the page fault
+ * queue are completed by the prq handling thread. Then follow the steps
+ * described in VT-d spec CH7.10 to drain all page requests and page
+ * responses pending in the hardware.
+ */
+void intel_iommu_drain_pasid_prq(struct device *dev, u32 pasid)
+{
+	struct device_domain_info *info;
+	struct dmar_domain *domain;
+	struct intel_iommu *iommu;
+	struct qi_desc desc[3];
+	int head, tail;
+	u16 sid, did;
+
+	info = dev_iommu_priv_get(dev);
+	if (!info->iopf_refcount)
+		return;
+
+	iommu = info->iommu;
+	domain = info->domain;
+	sid = PCI_DEVID(info->bus, info->devfn);
+	did = domain ? domain_id_iommu(domain, iommu) : FLPT_DEFAULT_DID;
+
+	/*
+	 * Check and wait until all pending page requests in the queue are
+	 * handled by the prq handling thread.
+	 */
+prq_retry:
+	reinit_completion(&iommu->prq_complete);
+	tail = readq(iommu->reg + DMAR_PQT_REG) & PRQ_RING_MASK;
+	head = readq(iommu->reg + DMAR_PQH_REG) & PRQ_RING_MASK;
+	while (head != tail) {
+		struct page_req_dsc *req;
+
+		req = &iommu->prq[head / sizeof(*req)];
+		if (req->rid != sid ||
+		    (req->pasid_present && pasid != req->pasid) ||
+		    (!req->pasid_present && pasid != IOMMU_NO_PASID)) {
+			head = (head + sizeof(*req)) & PRQ_RING_MASK;
+			continue;
+		}
+
+		wait_for_completion(&iommu->prq_complete);
+		goto prq_retry;
+	}
+
+	iopf_queue_flush_dev(dev);
+
+	/*
+	 * Perform steps described in VT-d spec CH7.10 to drain page
+	 * requests and responses in hardware.
+	 */
+	memset(desc, 0, sizeof(desc));
+	desc[0].qw0 = QI_IWD_STATUS_DATA(QI_DONE) |
+			QI_IWD_FENCE |
+			QI_IWD_TYPE;
+	if (pasid == IOMMU_NO_PASID) {
+		qi_desc_iotlb(iommu, did, 0, 0, DMA_TLB_DSI_FLUSH, &desc[1]);
+		qi_desc_dev_iotlb(sid, info->pfsid, info->ats_qdep, 0,
+				  MAX_AGAW_PFN_WIDTH, &desc[2]);
+	} else {
+		qi_desc_piotlb_all(did, pasid, &desc[1]);
+		qi_desc_dev_iotlb_pasid(sid, info->pfsid, pasid, info->ats_qdep,
+					0, MAX_AGAW_PFN_WIDTH, &desc[2]);
+	}
+qi_retry:
+	reinit_completion(&iommu->prq_complete);
+	qi_submit_sync(iommu, desc, 3, QI_OPT_WAIT_DRAIN);
+	if (readl(iommu->reg + DMAR_PRS_REG) & DMA_PRS_PRO) {
+		wait_for_completion(&iommu->prq_complete);
+		goto qi_retry;
+	}
+}
+
+static bool is_canonical_address(u64 addr)
+{
+	int shift = 64 - (__VIRTUAL_MASK_SHIFT + 1);
+	long saddr = (long)addr;
+
+	return (((saddr << shift) >> shift) == saddr);
+}
+
+static void handle_bad_prq_event(struct intel_iommu *iommu,
+				 struct page_req_dsc *req, int result)
+{
+	struct qi_desc desc = { };
+
+	pr_err("%s: Invalid page request: %08llx %08llx\n",
+	       iommu->name, ((unsigned long long *)req)[0],
+	       ((unsigned long long *)req)[1]);
+
+	if (!req->lpig)
+		return;
+
+	desc.qw0 = QI_PGRP_PASID(req->pasid) |
+			QI_PGRP_DID(req->rid) |
+			QI_PGRP_PASID_P(req->pasid_present) |
+			QI_PGRP_RESP_CODE(result) |
+			QI_PGRP_RESP_TYPE;
+	desc.qw1 = QI_PGRP_IDX(req->prg_index);
+
+	qi_submit_sync(iommu, &desc, 1, 0);
+}
+
+static int prq_to_iommu_prot(struct page_req_dsc *req)
+{
+	int prot = 0;
+
+	if (req->rd_req)
+		prot |= IOMMU_FAULT_PERM_READ;
+	if (req->wr_req)
+		prot |= IOMMU_FAULT_PERM_WRITE;
+	if (req->exe_req)
+		prot |= IOMMU_FAULT_PERM_EXEC;
+	if (req->pm_req)
+		prot |= IOMMU_FAULT_PERM_PRIV;
+
+	return prot;
+}
+
+static void intel_prq_report(struct intel_iommu *iommu, struct device *dev,
+			     struct page_req_dsc *desc)
+{
+	struct iopf_fault event = { };
+
+	/* Fill in event data for device specific processing */
+	event.fault.type = IOMMU_FAULT_PAGE_REQ;
+	event.fault.prm.addr = (u64)desc->addr << VTD_PAGE_SHIFT;
+	event.fault.prm.pasid = desc->pasid;
+	event.fault.prm.grpid = desc->prg_index;
+	event.fault.prm.perm = prq_to_iommu_prot(desc);
+
+	if (desc->lpig)
+		event.fault.prm.flags |= IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE;
+	if (desc->pasid_present) {
+		event.fault.prm.flags |= IOMMU_FAULT_PAGE_REQUEST_PASID_VALID;
+		event.fault.prm.flags |= IOMMU_FAULT_PAGE_RESPONSE_NEEDS_PASID;
+	}
+
+	iommu_report_device_fault(dev, &event);
+}
+
+static irqreturn_t prq_event_thread(int irq, void *d)
+{
+	struct intel_iommu *iommu = d;
+	struct page_req_dsc *req;
+	int head, tail, handled;
+	struct device *dev;
+	u64 address;
+
+	/*
+	 * Clear PPR bit before reading head/tail registers, to ensure that
+	 * we get a new interrupt if needed.
+	 */
+	writel(DMA_PRS_PPR, iommu->reg + DMAR_PRS_REG);
+
+	tail = readq(iommu->reg + DMAR_PQT_REG) & PRQ_RING_MASK;
+	head = readq(iommu->reg + DMAR_PQH_REG) & PRQ_RING_MASK;
+	handled = (head != tail);
+	while (head != tail) {
+		req = &iommu->prq[head / sizeof(*req)];
+		address = (u64)req->addr << VTD_PAGE_SHIFT;
+
+		if (unlikely(!is_canonical_address(address))) {
+			pr_err("IOMMU: %s: Address is not canonical\n",
+			       iommu->name);
+bad_req:
+			handle_bad_prq_event(iommu, req, QI_RESP_INVALID);
+			goto prq_advance;
+		}
+
+		if (unlikely(req->pm_req && (req->rd_req || req->wr_req))) {
+			pr_err("IOMMU: %s: Page request in Privilege Mode\n",
+			       iommu->name);
+			goto bad_req;
+		}
+
+		if (unlikely(req->exe_req && req->rd_req)) {
+			pr_err("IOMMU: %s: Execution request not supported\n",
+			       iommu->name);
+			goto bad_req;
+		}
+
+		/* Drop Stop Marker message. No need for a response. */
+		if (unlikely(req->lpig && !req->rd_req && !req->wr_req))
+			goto prq_advance;
+
+		/*
+		 * If prq is to be handled outside iommu driver via receiver of
+		 * the fault notifiers, we skip the page response here.
+		 */
+		mutex_lock(&iommu->iopf_lock);
+		dev = device_rbtree_find(iommu, req->rid);
+		if (!dev) {
+			mutex_unlock(&iommu->iopf_lock);
+			goto bad_req;
+		}
+
+		intel_prq_report(iommu, dev, req);
+		trace_prq_report(iommu, dev, req->qw_0, req->qw_1,
+				 req->qw_2, req->qw_3,
+				 iommu->prq_seq_number++);
+		mutex_unlock(&iommu->iopf_lock);
+prq_advance:
+		head = (head + sizeof(*req)) & PRQ_RING_MASK;
+	}
+
+	writeq(tail, iommu->reg + DMAR_PQH_REG);
+
+	/*
+	 * Clear the page request overflow bit and wake up all threads that
+	 * are waiting for the completion of this handling.
+	 */
+	if (readl(iommu->reg + DMAR_PRS_REG) & DMA_PRS_PRO) {
+		pr_info_ratelimited("IOMMU: %s: PRQ overflow detected\n",
+				    iommu->name);
+		head = readq(iommu->reg + DMAR_PQH_REG) & PRQ_RING_MASK;
+		tail = readq(iommu->reg + DMAR_PQT_REG) & PRQ_RING_MASK;
+		if (head == tail) {
+			iopf_queue_discard_partial(iommu->iopf_queue);
+			writel(DMA_PRS_PRO, iommu->reg + DMAR_PRS_REG);
+			pr_info_ratelimited("IOMMU: %s: PRQ overflow cleared",
+					    iommu->name);
+		}
+	}
+
+	if (!completion_done(&iommu->prq_complete))
+		complete(&iommu->prq_complete);
+
+	return IRQ_RETVAL(handled);
+}
+
+int intel_iommu_enable_prq(struct intel_iommu *iommu)
+{
+	struct iopf_queue *iopfq;
+	int irq, ret;
+
+	iommu->prq =
+		iommu_alloc_pages_node_sz(iommu->node, GFP_KERNEL, PRQ_SIZE);
+	if (!iommu->prq) {
+		pr_warn("IOMMU: %s: Failed to allocate page request queue\n",
+			iommu->name);
+		return -ENOMEM;
+	}
+
+	irq = dmar_alloc_hwirq(IOMMU_IRQ_ID_OFFSET_PRQ + iommu->seq_id, iommu->node, iommu);
+	if (irq <= 0) {
+		pr_err("IOMMU: %s: Failed to create IRQ vector for page request queue\n",
+		       iommu->name);
+		ret = -EINVAL;
+		goto free_prq;
+	}
+	iommu->pr_irq = irq;
+
+	snprintf(iommu->iopfq_name, sizeof(iommu->iopfq_name),
+		 "dmar%d-iopfq", iommu->seq_id);
+	iopfq = iopf_queue_alloc(iommu->iopfq_name);
+	if (!iopfq) {
+		pr_err("IOMMU: %s: Failed to allocate iopf queue\n", iommu->name);
+		ret = -ENOMEM;
+		goto free_hwirq;
+	}
+	iommu->iopf_queue = iopfq;
+
+	snprintf(iommu->prq_name, sizeof(iommu->prq_name), "dmar%d-prq", iommu->seq_id);
+
+	ret = request_threaded_irq(irq, NULL, prq_event_thread, IRQF_ONESHOT,
+				   iommu->prq_name, iommu);
+	if (ret) {
+		pr_err("IOMMU: %s: Failed to request IRQ for page request queue\n",
+		       iommu->name);
+		goto free_iopfq;
+	}
+	writeq(0ULL, iommu->reg + DMAR_PQH_REG);
+	writeq(0ULL, iommu->reg + DMAR_PQT_REG);
+	writeq(virt_to_phys(iommu->prq) | PRQ_ORDER, iommu->reg + DMAR_PQA_REG);
+
+	init_completion(&iommu->prq_complete);
+
+	return 0;
+
+free_iopfq:
+	iopf_queue_free(iommu->iopf_queue);
+	iommu->iopf_queue = NULL;
+free_hwirq:
+	dmar_free_hwirq(irq);
+	iommu->pr_irq = 0;
+free_prq:
+	iommu_free_pages(iommu->prq);
+	iommu->prq = NULL;
+
+	return ret;
+}
+
+int intel_iommu_finish_prq(struct intel_iommu *iommu)
+{
+	writeq(0ULL, iommu->reg + DMAR_PQH_REG);
+	writeq(0ULL, iommu->reg + DMAR_PQT_REG);
+	writeq(0ULL, iommu->reg + DMAR_PQA_REG);
+
+	if (iommu->pr_irq) {
+		free_irq(iommu->pr_irq, iommu);
+		dmar_free_hwirq(iommu->pr_irq);
+		iommu->pr_irq = 0;
+	}
+
+	if (iommu->iopf_queue) {
+		iopf_queue_free(iommu->iopf_queue);
+		iommu->iopf_queue = NULL;
+	}
+
+	iommu_free_pages(iommu->prq);
+	iommu->prq = NULL;
+
+	return 0;
+}
+
+void intel_iommu_page_response(struct device *dev, struct iopf_fault *evt,
+			       struct iommu_page_response *msg)
+{
+	struct device_domain_info *info = dev_iommu_priv_get(dev);
+	struct intel_iommu *iommu = info->iommu;
+	u8 bus = info->bus, devfn = info->devfn;
+	struct iommu_fault_page_request *prm;
+	struct qi_desc desc;
+	bool pasid_present;
+	u16 sid;
+
+	prm = &evt->fault.prm;
+	sid = PCI_DEVID(bus, devfn);
+	pasid_present = prm->flags & IOMMU_FAULT_PAGE_REQUEST_PASID_VALID;
+
+	desc.qw0 = QI_PGRP_PASID(prm->pasid) | QI_PGRP_DID(sid) |
+			QI_PGRP_PASID_P(pasid_present) |
+			QI_PGRP_RESP_CODE(msg->code) |
+			QI_PGRP_RESP_TYPE;
+	desc.qw1 = QI_PGRP_IDX(prm->grpid);
+	desc.qw2 = 0;
+	desc.qw3 = 0;
+
+	qi_submit_sync(iommu, &desc, 1, 0);
+}