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, 136 insertions, 0 deletions

diff --git a/arch/csky/mm/cachev1.c b/arch/csky/mm/cachev1.c
new file mode 100644
index 000000000..5a5a9804a
--- /dev/null
+++ b/arch/csky/mm/cachev1.c
@@ -0,0 +1,136 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
+
+#include <linux/spinlock.h>
+#include <asm/cache.h>
+#include <abi/reg_ops.h>
+
+/* for L1-cache */
+#define INS_CACHE		(1 << 0)
+#define DATA_CACHE		(1 << 1)
+#define CACHE_INV		(1 << 4)
+#define CACHE_CLR		(1 << 5)
+#define CACHE_OMS		(1 << 6)
+#define CACHE_ITS		(1 << 7)
+#define CACHE_LICF		(1 << 31)
+
+/* for L2-cache */
+#define CR22_LEVEL_SHIFT	(1)
+#define CR22_SET_SHIFT		(7)
+#define CR22_WAY_SHIFT		(30)
+#define CR22_WAY_SHIFT_L2	(29)
+
+static DEFINE_SPINLOCK(cache_lock);
+
+static inline void cache_op_line(unsigned long i, unsigned int val)
+{
+	mtcr("cr22", i);
+	mtcr("cr17", val);
+}
+
+#define CCR2_L2E (1 << 3)
+static void cache_op_all(unsigned int value, unsigned int l2)
+{
+	mtcr("cr17", value | CACHE_CLR);
+	mb();
+
+	if (l2 && (mfcr_ccr2() & CCR2_L2E)) {
+		mtcr("cr24", value | CACHE_CLR);
+		mb();
+	}
+}
+
+static void cache_op_range(
+	unsigned int start,
+	unsigned int end,
+	unsigned int value,
+	unsigned int l2)
+{
+	unsigned long i, flags;
+	unsigned int val = value | CACHE_CLR | CACHE_OMS;
+	bool l2_sync;
+
+	if (unlikely((end - start) >= PAGE_SIZE) ||
+	    unlikely(start < PAGE_OFFSET) ||
+	    unlikely(start >= PAGE_OFFSET + LOWMEM_LIMIT)) {
+		cache_op_all(value, l2);
+		return;
+	}
+
+	if ((mfcr_ccr2() & CCR2_L2E) && l2)
+		l2_sync = 1;
+	else
+		l2_sync = 0;
+
+	spin_lock_irqsave(&cache_lock, flags);
+
+	i = start & ~(L1_CACHE_BYTES - 1);
+	for (; i < end; i += L1_CACHE_BYTES) {
+		cache_op_line(i, val);
+		if (l2_sync) {
+			mb();
+			mtcr("cr24", val);
+		}
+	}
+	spin_unlock_irqrestore(&cache_lock, flags);
+
+	mb();
+}
+
+void dcache_wb_line(unsigned long start)
+{
+	asm volatile("idly4\n":::"memory");
+	cache_op_line(start, DATA_CACHE|CACHE_CLR);
+	mb();
+}
+
+void icache_inv_range(unsigned long start, unsigned long end)
+{
+	cache_op_range(start, end, INS_CACHE|CACHE_INV, 0);
+}
+
+void icache_inv_all(void)
+{
+	cache_op_all(INS_CACHE|CACHE_INV, 0);
+}
+
+void local_icache_inv_all(void *priv)
+{
+	cache_op_all(INS_CACHE|CACHE_INV, 0);
+}
+
+void dcache_wb_range(unsigned long start, unsigned long end)
+{
+	cache_op_range(start, end, DATA_CACHE|CACHE_CLR, 0);
+}
+
+void dcache_wbinv_all(void)
+{
+	cache_op_all(DATA_CACHE|CACHE_CLR|CACHE_INV, 0);
+}
+
+void cache_wbinv_range(unsigned long start, unsigned long end)
+{
+	cache_op_range(start, end, INS_CACHE|DATA_CACHE|CACHE_CLR|CACHE_INV, 0);
+}
+EXPORT_SYMBOL(cache_wbinv_range);
+
+void cache_wbinv_all(void)
+{
+	cache_op_all(INS_CACHE|DATA_CACHE|CACHE_CLR|CACHE_INV, 0);
+}
+
+void dma_wbinv_range(unsigned long start, unsigned long end)
+{
+	cache_op_range(start, end, DATA_CACHE|CACHE_CLR|CACHE_INV, 1);
+}
+
+void dma_inv_range(unsigned long start, unsigned long end)
+{
+	cache_op_range(start, end, DATA_CACHE|CACHE_CLR|CACHE_INV, 1);
+}
+
+void dma_wb_range(unsigned long start, unsigned long end)
+{
+	cache_op_range(start, end, DATA_CACHE|CACHE_CLR|CACHE_INV, 1);
+}