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, 304 insertions, 0 deletions

diff --git a/drivers/scsi/a2091.c b/drivers/scsi/a2091.c
new file mode 100644
index 000000000..f81e53b53
--- /dev/null
+++ b/drivers/scsi/a2091.c
@@ -0,0 +1,304 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/zorro.h>
+#include <linux/module.h>
+
+#include <asm/page.h>
+#include <asm/amigaints.h>
+#include <asm/amigahw.h>
+
+#include <scsi/scsi.h>
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_eh.h>
+#include <scsi/scsi_tcq.h>
+#include "wd33c93.h"
+#include "a2091.h"
+
+
+struct a2091_hostdata {
+	struct WD33C93_hostdata wh;
+	struct a2091_scsiregs *regs;
+	struct device *dev;
+};
+
+#define DMA_DIR(d)   ((d == DATA_OUT_DIR) ? DMA_TO_DEVICE : DMA_FROM_DEVICE)
+
+static irqreturn_t a2091_intr(int irq, void *data)
+{
+	struct Scsi_Host *instance = data;
+	struct a2091_hostdata *hdata = shost_priv(instance);
+	unsigned int status = hdata->regs->ISTR;
+	unsigned long flags;
+
+	if (!(status & (ISTR_INT_F | ISTR_INT_P)) || !(status & ISTR_INTS))
+		return IRQ_NONE;
+
+	spin_lock_irqsave(instance->host_lock, flags);
+	wd33c93_intr(instance);
+	spin_unlock_irqrestore(instance->host_lock, flags);
+	return IRQ_HANDLED;
+}
+
+static int dma_setup(struct scsi_cmnd *cmd, int dir_in)
+{
+	struct scsi_pointer *scsi_pointer = WD33C93_scsi_pointer(cmd);
+	unsigned long len = scsi_pointer->this_residual;
+	struct Scsi_Host *instance = cmd->device->host;
+	struct a2091_hostdata *hdata = shost_priv(instance);
+	struct WD33C93_hostdata *wh = &hdata->wh;
+	struct a2091_scsiregs *regs = hdata->regs;
+	unsigned short cntr = CNTR_PDMD | CNTR_INTEN;
+	dma_addr_t addr;
+
+	addr = dma_map_single(hdata->dev, scsi_pointer->ptr,
+			      len, DMA_DIR(dir_in));
+	if (dma_mapping_error(hdata->dev, addr)) {
+		dev_warn(hdata->dev, "cannot map SCSI data block %p\n",
+			 scsi_pointer->ptr);
+		return 1;
+	}
+	scsi_pointer->dma_handle = addr;
+
+	/* don't allow DMA if the physical address is bad */
+	if (addr & A2091_XFER_MASK) {
+		/* drop useless mapping */
+		dma_unmap_single(hdata->dev, scsi_pointer->dma_handle,
+				 scsi_pointer->this_residual,
+				 DMA_DIR(dir_in));
+		scsi_pointer->dma_handle = (dma_addr_t) NULL;
+
+		wh->dma_bounce_len = (scsi_pointer->this_residual + 511) & ~0x1ff;
+		wh->dma_bounce_buffer = kmalloc(wh->dma_bounce_len,
+						GFP_KERNEL);
+
+		/* can't allocate memory; use PIO */
+		if (!wh->dma_bounce_buffer) {
+			wh->dma_bounce_len = 0;
+			return 1;
+		}
+
+		if (!dir_in) {
+			/* copy to bounce buffer for a write */
+			memcpy(wh->dma_bounce_buffer, scsi_pointer->ptr,
+			       scsi_pointer->this_residual);
+		}
+
+		/* will flush/invalidate cache for us */
+		addr = dma_map_single(hdata->dev, wh->dma_bounce_buffer,
+				      wh->dma_bounce_len, DMA_DIR(dir_in));
+		/* can't map buffer; use PIO */
+		if (dma_mapping_error(hdata->dev, addr)) {
+			dev_warn(hdata->dev, "cannot map bounce buffer %p\n",
+				 wh->dma_bounce_buffer);
+			return 1;
+		}
+
+		/* the bounce buffer may not be in the first 16M of physmem */
+		if (addr & A2091_XFER_MASK) {
+			/* we could use chipmem... maybe later */
+			kfree(wh->dma_bounce_buffer);
+			wh->dma_bounce_buffer = NULL;
+			wh->dma_bounce_len = 0;
+			return 1;
+		}
+
+		scsi_pointer->dma_handle = addr;
+	}
+
+	/* setup dma direction */
+	if (!dir_in)
+		cntr |= CNTR_DDIR;
+
+	/* remember direction */
+	wh->dma_dir = dir_in;
+
+	regs->CNTR = cntr;
+
+	/* setup DMA *physical* address */
+	regs->ACR = addr;
+
+	/* no more cache flush here - dma_map_single() takes care */
+
+	/* start DMA */
+	regs->ST_DMA = 1;
+
+	/* return success */
+	return 0;
+}
+
+static void dma_stop(struct Scsi_Host *instance, struct scsi_cmnd *SCpnt,
+		     int status)
+{
+	struct scsi_pointer *scsi_pointer = WD33C93_scsi_pointer(SCpnt);
+	struct a2091_hostdata *hdata = shost_priv(instance);
+	struct WD33C93_hostdata *wh = &hdata->wh;
+	struct a2091_scsiregs *regs = hdata->regs;
+
+	/* disable SCSI interrupts */
+	unsigned short cntr = CNTR_PDMD;
+
+	if (!wh->dma_dir)
+		cntr |= CNTR_DDIR;
+
+	/* disable SCSI interrupts */
+	regs->CNTR = cntr;
+
+	/* flush if we were reading */
+	if (wh->dma_dir) {
+		regs->FLUSH = 1;
+		while (!(regs->ISTR & ISTR_FE_FLG))
+			;
+	}
+
+	/* clear a possible interrupt */
+	regs->CINT = 1;
+
+	/* stop DMA */
+	regs->SP_DMA = 1;
+
+	/* restore the CONTROL bits (minus the direction flag) */
+	regs->CNTR = CNTR_PDMD | CNTR_INTEN;
+
+	dma_unmap_single(hdata->dev, scsi_pointer->dma_handle,
+			 scsi_pointer->this_residual,
+			 DMA_DIR(wh->dma_dir));
+
+	/* copy from a bounce buffer, if necessary */
+	if (status && wh->dma_bounce_buffer) {
+		if (wh->dma_dir)
+			memcpy(scsi_pointer->ptr, wh->dma_bounce_buffer,
+			       scsi_pointer->this_residual);
+		kfree(wh->dma_bounce_buffer);
+		wh->dma_bounce_buffer = NULL;
+		wh->dma_bounce_len = 0;
+	}
+}
+
+static const struct scsi_host_template a2091_scsi_template = {
+	.module			= THIS_MODULE,
+	.name			= "Commodore A2091/A590 SCSI",
+	.show_info		= wd33c93_show_info,
+	.write_info		= wd33c93_write_info,
+	.proc_name		= "A2901",
+	.queuecommand		= wd33c93_queuecommand,
+	.eh_abort_handler	= wd33c93_abort,
+	.eh_host_reset_handler	= wd33c93_host_reset,
+	.can_queue		= CAN_QUEUE,
+	.this_id		= 7,
+	.sg_tablesize		= SG_ALL,
+	.cmd_per_lun		= CMD_PER_LUN,
+	.dma_boundary		= PAGE_SIZE - 1,
+	.cmd_size		= sizeof(struct scsi_pointer),
+};
+
+static int a2091_probe(struct zorro_dev *z, const struct zorro_device_id *ent)
+{
+	struct Scsi_Host *instance;
+	int error;
+	struct a2091_scsiregs *regs;
+	wd33c93_regs wdregs;
+	struct a2091_hostdata *hdata;
+
+	if (dma_set_mask_and_coherent(&z->dev, DMA_BIT_MASK(24))) {
+		dev_warn(&z->dev, "cannot use 24 bit DMA\n");
+		return -ENODEV;
+	}
+
+	if (!request_mem_region(z->resource.start, 256, "wd33c93"))
+		return -EBUSY;
+
+	instance = scsi_host_alloc(&a2091_scsi_template,
+				   sizeof(struct a2091_hostdata));
+	if (!instance) {
+		error = -ENOMEM;
+		goto fail_alloc;
+	}
+
+	instance->irq = IRQ_AMIGA_PORTS;
+	instance->unique_id = z->slotaddr;
+
+	regs = ZTWO_VADDR(z->resource.start);
+	regs->DAWR = DAWR_A2091;
+
+	wdregs.SASR = &regs->SASR;
+	wdregs.SCMD = &regs->SCMD;
+
+	hdata = shost_priv(instance);
+	hdata->dev = &z->dev;
+	hdata->wh.no_sync = 0xff;
+	hdata->wh.fast = 0;
+	hdata->wh.dma_mode = CTRL_DMA;
+	hdata->regs = regs;
+
+	wd33c93_init(instance, wdregs, dma_setup, dma_stop, WD33C93_FS_8_10);
+	error = request_irq(IRQ_AMIGA_PORTS, a2091_intr, IRQF_SHARED,
+			    "A2091 SCSI", instance);
+	if (error)
+		goto fail_irq;
+
+	regs->CNTR = CNTR_PDMD | CNTR_INTEN;
+
+	error = scsi_add_host(instance, NULL);
+	if (error)
+		goto fail_host;
+
+	zorro_set_drvdata(z, instance);
+
+	scsi_scan_host(instance);
+	return 0;
+
+fail_host:
+	free_irq(IRQ_AMIGA_PORTS, instance);
+fail_irq:
+	scsi_host_put(instance);
+fail_alloc:
+	release_mem_region(z->resource.start, 256);
+	return error;
+}
+
+static void a2091_remove(struct zorro_dev *z)
+{
+	struct Scsi_Host *instance = zorro_get_drvdata(z);
+	struct a2091_hostdata *hdata = shost_priv(instance);
+
+	hdata->regs->CNTR = 0;
+	scsi_remove_host(instance);
+	free_irq(IRQ_AMIGA_PORTS, instance);
+	scsi_host_put(instance);
+	release_mem_region(z->resource.start, 256);
+}
+
+static struct zorro_device_id a2091_zorro_tbl[] = {
+	{ .id = ZORRO_PROD_CBM_A590_A2091_1 },
+	{ .id = ZORRO_PROD_CBM_A590_A2091_2 },
+	{ }
+};
+MODULE_DEVICE_TABLE(zorro, a2091_zorro_tbl);
+
+static struct zorro_driver a2091_driver = {
+	.name		= "a2091",
+	.id_table	= a2091_zorro_tbl,
+	.probe		= a2091_probe,
+	.remove		= a2091_remove,
+};
+
+static int __init a2091_init(void)
+{
+	return zorro_register_driver(&a2091_driver);
+}
+module_init(a2091_init);
+
+static void __exit a2091_exit(void)
+{
+	zorro_unregister_driver(&a2091_driver);
+}
+module_exit(a2091_exit);
+
+MODULE_DESCRIPTION("Commodore A2091/A590 SCSI");
+MODULE_LICENSE("GPL");