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, 264 insertions, 0 deletions

diff --git a/arch/mips/mm/sc-mips.c b/arch/mips/mm/sc-mips.c
new file mode 100644
index 000000000..06ec304ad
--- /dev/null
+++ b/arch/mips/mm/sc-mips.c
@@ -0,0 +1,264 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2006 Chris Dearman (chris@mips.com),
+ */
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+
+#include <asm/cpu-type.h>
+#include <asm/mipsregs.h>
+#include <asm/bcache.h>
+#include <asm/cacheops.h>
+#include <asm/page.h>
+#include <asm/mmu_context.h>
+#include <asm/r4kcache.h>
+#include <asm/mips-cps.h>
+#include <asm/bootinfo.h>
+
+/*
+ * MIPS32/MIPS64 L2 cache handling
+ */
+
+/*
+ * Writeback and invalidate the secondary cache before DMA.
+ */
+static void mips_sc_wback_inv(unsigned long addr, unsigned long size)
+{
+	blast_scache_range(addr, addr + size);
+}
+
+/*
+ * Invalidate the secondary cache before DMA.
+ */
+static void mips_sc_inv(unsigned long addr, unsigned long size)
+{
+	unsigned long lsize = cpu_scache_line_size();
+	unsigned long almask = ~(lsize - 1);
+
+	cache_op(Hit_Writeback_Inv_SD, addr & almask);
+	cache_op(Hit_Writeback_Inv_SD, (addr + size - 1) & almask);
+	blast_inv_scache_range(addr, addr + size);
+}
+
+static void mips_sc_enable(void)
+{
+	/* L2 cache is permanently enabled */
+}
+
+static void mips_sc_disable(void)
+{
+	/* L2 cache is permanently enabled */
+}
+
+static void mips_sc_prefetch_enable(void)
+{
+	unsigned long pftctl;
+
+	if (mips_cm_revision() < CM_REV_CM2_5)
+		return;
+
+	/*
+	 * If there is one or more L2 prefetch unit present then enable
+	 * prefetching for both code & data, for all ports.
+	 */
+	pftctl = read_gcr_l2_pft_control();
+	if (pftctl & CM_GCR_L2_PFT_CONTROL_NPFT) {
+		pftctl &= ~CM_GCR_L2_PFT_CONTROL_PAGEMASK;
+		pftctl |= PAGE_MASK & CM_GCR_L2_PFT_CONTROL_PAGEMASK;
+		pftctl |= CM_GCR_L2_PFT_CONTROL_PFTEN;
+		write_gcr_l2_pft_control(pftctl);
+
+		set_gcr_l2_pft_control_b(CM_GCR_L2_PFT_CONTROL_B_PORTID |
+					 CM_GCR_L2_PFT_CONTROL_B_CEN);
+	}
+}
+
+static void mips_sc_prefetch_disable(void)
+{
+	if (mips_cm_revision() < CM_REV_CM2_5)
+		return;
+
+	clear_gcr_l2_pft_control(CM_GCR_L2_PFT_CONTROL_PFTEN);
+	clear_gcr_l2_pft_control_b(CM_GCR_L2_PFT_CONTROL_B_PORTID |
+				   CM_GCR_L2_PFT_CONTROL_B_CEN);
+}
+
+static bool mips_sc_prefetch_is_enabled(void)
+{
+	unsigned long pftctl;
+
+	if (mips_cm_revision() < CM_REV_CM2_5)
+		return false;
+
+	pftctl = read_gcr_l2_pft_control();
+	if (!(pftctl & CM_GCR_L2_PFT_CONTROL_NPFT))
+		return false;
+	return !!(pftctl & CM_GCR_L2_PFT_CONTROL_PFTEN);
+}
+
+static struct bcache_ops mips_sc_ops = {
+	.bc_enable = mips_sc_enable,
+	.bc_disable = mips_sc_disable,
+	.bc_wback_inv = mips_sc_wback_inv,
+	.bc_inv = mips_sc_inv,
+	.bc_prefetch_enable = mips_sc_prefetch_enable,
+	.bc_prefetch_disable = mips_sc_prefetch_disable,
+	.bc_prefetch_is_enabled = mips_sc_prefetch_is_enabled,
+};
+
+/*
+ * Check if the L2 cache controller is activated on a particular platform.
+ * MTI's L2 controller and the L2 cache controller of Broadcom's BMIPS
+ * cores both use c0_config2's bit 12 as "L2 Bypass" bit, that is the
+ * cache being disabled.  However there is no guarantee for this to be
+ * true on all platforms.  In an act of stupidity the spec defined bits
+ * 12..15 as implementation defined so below function will eventually have
+ * to be replaced by a platform specific probe.
+ */
+static inline int mips_sc_is_activated(struct cpuinfo_mips *c)
+{
+	unsigned int config2 = read_c0_config2();
+	unsigned int tmp;
+
+	/* Check the bypass bit (L2B) */
+	switch (current_cpu_type()) {
+	case CPU_34K:
+	case CPU_74K:
+	case CPU_1004K:
+	case CPU_1074K:
+	case CPU_INTERAPTIV:
+	case CPU_PROAPTIV:
+	case CPU_P5600:
+	case CPU_BMIPS5000:
+	case CPU_QEMU_GENERIC:
+	case CPU_P6600:
+		if (config2 & (1 << 12))
+			return 0;
+	}
+
+	tmp = (config2 >> 4) & 0x0f;
+	if (0 < tmp && tmp <= 7)
+		c->scache.linesz = 2 << tmp;
+	else
+		return 0;
+	return 1;
+}
+
+static int mips_sc_probe_cm3(void)
+{
+	struct cpuinfo_mips *c = &current_cpu_data;
+	unsigned long cfg = read_gcr_l2_config();
+	unsigned long sets, line_sz, assoc;
+
+	if (cfg & CM_GCR_L2_CONFIG_BYPASS)
+		return 0;
+
+	sets = cfg & CM_GCR_L2_CONFIG_SET_SIZE;
+	sets >>= __ffs(CM_GCR_L2_CONFIG_SET_SIZE);
+	if (sets)
+		c->scache.sets = 64 << sets;
+
+	line_sz = cfg & CM_GCR_L2_CONFIG_LINE_SIZE;
+	line_sz >>= __ffs(CM_GCR_L2_CONFIG_LINE_SIZE);
+	if (line_sz)
+		c->scache.linesz = 2 << line_sz;
+
+	assoc = cfg & CM_GCR_L2_CONFIG_ASSOC;
+	assoc >>= __ffs(CM_GCR_L2_CONFIG_ASSOC);
+	c->scache.ways = assoc + 1;
+	c->scache.waysize = c->scache.sets * c->scache.linesz;
+	c->scache.waybit = __ffs(c->scache.waysize);
+
+	if (c->scache.linesz) {
+		c->scache.flags &= ~MIPS_CACHE_NOT_PRESENT;
+		c->options |= MIPS_CPU_INCLUSIVE_CACHES;
+		return 1;
+	}
+
+	return 0;
+}
+
+static inline int mips_sc_probe(void)
+{
+	struct cpuinfo_mips *c = &current_cpu_data;
+	unsigned int config1, config2;
+	unsigned int tmp;
+
+	/* Mark as not present until probe completed */
+	c->scache.flags |= MIPS_CACHE_NOT_PRESENT;
+
+	if (mips_cm_revision() >= CM_REV_CM3)
+		return mips_sc_probe_cm3();
+
+	/* Ignore anything but MIPSxx processors */
+	if (!(c->isa_level & (MIPS_CPU_ISA_M32R1 | MIPS_CPU_ISA_M64R1 |
+			      MIPS_CPU_ISA_M32R2 | MIPS_CPU_ISA_M64R2 |
+			      MIPS_CPU_ISA_M32R5 | MIPS_CPU_ISA_M64R5 |
+			      MIPS_CPU_ISA_M32R6 | MIPS_CPU_ISA_M64R6)))
+		return 0;
+
+	/* Does this MIPS32/MIPS64 CPU have a config2 register? */
+	config1 = read_c0_config1();
+	if (!(config1 & MIPS_CONF_M))
+		return 0;
+
+	config2 = read_c0_config2();
+
+	if (!mips_sc_is_activated(c))
+		return 0;
+
+	tmp = (config2 >> 8) & 0x0f;
+	if (tmp <= 7)
+		c->scache.sets = 64 << tmp;
+	else
+		return 0;
+
+	tmp = (config2 >> 0) & 0x0f;
+	if (tmp <= 7)
+		c->scache.ways = tmp + 1;
+	else
+		return 0;
+
+	if (current_cpu_type() == CPU_XBURST) {
+		switch (mips_machtype) {
+		/*
+		 * According to config2 it would be 5-ways, but that is
+		 * contradicted by all documentation.
+		 */
+		case MACH_INGENIC_JZ4770:
+		case MACH_INGENIC_JZ4775:
+			c->scache.ways = 4;
+			break;
+
+		/*
+		 * According to config2 it would be 5-ways and 512-sets,
+		 * but that is contradicted by all documentation.
+		 */
+		case MACH_INGENIC_X1000:
+		case MACH_INGENIC_X1000E:
+			c->scache.sets = 256;
+			c->scache.ways = 4;
+			break;
+		}
+	}
+
+	c->scache.waysize = c->scache.sets * c->scache.linesz;
+	c->scache.waybit = __ffs(c->scache.waysize);
+
+	c->scache.flags &= ~MIPS_CACHE_NOT_PRESENT;
+
+	return 1;
+}
+
+int mips_sc_init(void)
+{
+	int found = mips_sc_probe();
+	if (found) {
+		mips_sc_enable();
+		mips_sc_prefetch_enable();
+		bcops = &mips_sc_ops;
+	}
+	return found;
+}