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, 118 insertions, 0 deletions

diff --git a/drivers/edac/sifive_edac.c b/drivers/edac/sifive_edac.c
new file mode 100644
index 000000000..a2b193dc6
--- /dev/null
+++ b/drivers/edac/sifive_edac.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SiFive Platform EDAC Driver
+ *
+ * Copyright (C) 2018-2022 SiFive, Inc.
+ *
+ * This driver is partially based on octeon_edac-pc.c
+ *
+ */
+#include <linux/edac.h>
+#include <linux/platform_device.h>
+#include "edac_module.h"
+#include <soc/sifive/sifive_ccache.h>
+
+#define DRVNAME "sifive_edac"
+
+struct sifive_edac_priv {
+	struct notifier_block notifier;
+	struct edac_device_ctl_info *dci;
+};
+
+/*
+ * EDAC error callback
+ *
+ * @event: non-zero if unrecoverable.
+ */
+static
+int ecc_err_event(struct notifier_block *this, unsigned long event, void *ptr)
+{
+	const char *msg = (char *)ptr;
+	struct sifive_edac_priv *p;
+
+	p = container_of(this, struct sifive_edac_priv, notifier);
+
+	if (event == SIFIVE_CCACHE_ERR_TYPE_UE)
+		edac_device_handle_ue(p->dci, 0, 0, msg);
+	else if (event == SIFIVE_CCACHE_ERR_TYPE_CE)
+		edac_device_handle_ce(p->dci, 0, 0, msg);
+
+	return NOTIFY_OK;
+}
+
+static int ecc_register(struct platform_device *pdev)
+{
+	struct sifive_edac_priv *p;
+
+	p = devm_kzalloc(&pdev->dev, sizeof(*p), GFP_KERNEL);
+	if (!p)
+		return -ENOMEM;
+
+	p->notifier.notifier_call = ecc_err_event;
+	platform_set_drvdata(pdev, p);
+
+	p->dci = edac_device_alloc_ctl_info(0, "sifive_ecc", 1, "sifive_ecc",
+					    1, 1, edac_device_alloc_index());
+	if (!p->dci)
+		return -ENOMEM;
+
+	p->dci->dev = &pdev->dev;
+	p->dci->mod_name = "Sifive ECC Manager";
+	p->dci->ctl_name = dev_name(&pdev->dev);
+	p->dci->dev_name = dev_name(&pdev->dev);
+
+	if (edac_device_add_device(p->dci)) {
+		dev_err(p->dci->dev, "failed to register with EDAC core\n");
+		goto err;
+	}
+
+	register_sifive_ccache_error_notifier(&p->notifier);
+
+	return 0;
+
+err:
+	edac_device_free_ctl_info(p->dci);
+
+	return -ENXIO;
+}
+
+static int ecc_unregister(struct platform_device *pdev)
+{
+	struct sifive_edac_priv *p = platform_get_drvdata(pdev);
+
+	unregister_sifive_ccache_error_notifier(&p->notifier);
+	edac_device_del_device(&pdev->dev);
+	edac_device_free_ctl_info(p->dci);
+
+	return 0;
+}
+
+static struct platform_device *sifive_pdev;
+
+static int __init sifive_edac_init(void)
+{
+	int ret;
+
+	sifive_pdev = platform_device_register_simple(DRVNAME, 0, NULL, 0);
+	if (IS_ERR(sifive_pdev))
+		return PTR_ERR(sifive_pdev);
+
+	ret = ecc_register(sifive_pdev);
+	if (ret)
+		platform_device_unregister(sifive_pdev);
+
+	return ret;
+}
+
+static void __exit sifive_edac_exit(void)
+{
+	ecc_unregister(sifive_pdev);
+	platform_device_unregister(sifive_pdev);
+}
+
+module_init(sifive_edac_init);
+module_exit(sifive_edac_exit);
+
+MODULE_AUTHOR("SiFive Inc.");
+MODULE_DESCRIPTION("SiFive platform EDAC driver");
+MODULE_LICENSE("GPL v2");