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, 105 insertions, 0 deletions

diff --git a/drivers/parisc/hppb.c b/drivers/parisc/hppb.c
new file mode 100644
index 000000000..33709eafe
--- /dev/null
+++ b/drivers/parisc/hppb.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+** hppb.c:
+**      HP-PB bus driver for the NOVA and K-Class systems.
+**
+**      (c) Copyright 2002 Ryan Bradetich
+**      (c) Copyright 2002 Hewlett-Packard Company
+**
+**
+*/
+
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/dma-mapping.h>
+#include <linux/ioport.h>
+
+#include <asm/io.h>
+#include <asm/hardware.h>
+#include <asm/parisc-device.h>
+
+#include "iommu.h"
+
+struct hppb_card {
+	unsigned long hpa;
+	struct resource mmio_region;
+	struct hppb_card *next;
+};
+
+static struct hppb_card hppb_card_head = {
+	.hpa = 0,
+	.next = NULL,
+};
+
+#define IO_IO_LOW  offsetof(struct bc_module, io_io_low)
+#define IO_IO_HIGH offsetof(struct bc_module, io_io_high)
+
+/**
+ * hppb_probe - Determine if the hppb driver should claim this device.
+ * @dev: The device which has been found
+ *
+ * Determine if hppb driver should claim this chip (return 0) or not 
+ * (return 1). If so, initialize the chip and tell other partners in crime 
+ * they have work to do.
+ */
+static int __init hppb_probe(struct parisc_device *dev)
+{
+	int status;
+	struct hppb_card *card = &hppb_card_head;
+
+	while(card->next) {
+		card = card->next;
+	}
+
+	if(card->hpa) {
+		card->next = kzalloc_obj(struct hppb_card);
+		if(!card->next) {
+			printk(KERN_ERR "HP-PB: Unable to allocate memory.\n");
+			return 1;
+		}
+		card = card->next;
+	}
+
+	card->hpa = dev->hpa.start;
+	card->mmio_region.name = "HP-PB Bus";
+	card->mmio_region.flags = IORESOURCE_MEM;
+
+	card->mmio_region.start = gsc_readl(dev->hpa.start + IO_IO_LOW);
+	card->mmio_region.end = gsc_readl(dev->hpa.start + IO_IO_HIGH) - 1;
+
+	status = ccio_request_resource(dev, &card->mmio_region);
+
+	pr_info("Found GeckoBoa at %pap, bus space %pR,%s claimed.\n",
+			&dev->hpa.start,
+			&card->mmio_region,
+			(status < 0) ? " not":"" );
+
+        return 0;
+}
+
+static const struct parisc_device_id hppb_tbl[] __initconst = {
+        { HPHW_BCPORT, HVERSION_REV_ANY_ID, 0x500, 0xc }, /* E25 and K */
+        { HPHW_BCPORT, 0x0, 0x501, 0xc }, /* E35 */
+        { HPHW_BCPORT, 0x0, 0x502, 0xc }, /* E45 */
+        { HPHW_BCPORT, 0x0, 0x503, 0xc }, /* E55 */
+        { 0, }
+};
+
+static struct parisc_driver hppb_driver __refdata = {
+        .name =         "gecko_boa",
+        .id_table =     hppb_tbl,
+	.probe =        hppb_probe,
+};
+
+/**
+ * hppb_init - HP-PB bus initialization procedure.
+ *
+ * Register this driver.
+ */
+static int __init hppb_init(void)
+{
+        return register_parisc_driver(&hppb_driver);
+}
+arch_initcall(hppb_init);