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, 41 insertions, 0 deletions

diff --git a/drivers/net/phy/phylib.h b/drivers/net/phy/phylib.h
new file mode 100644
index 000000000..c6e26ac6b
--- /dev/null
+++ b/drivers/net/phy/phylib.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * phylib header
+ */
+
+#ifndef __PHYLIB_H
+#define __PHYLIB_H
+
+struct device_node;
+struct phy_device;
+struct mii_bus;
+
+struct device_node *phy_package_get_node(struct phy_device *phydev);
+void *phy_package_get_priv(struct phy_device *phydev);
+void phy_package_lock(struct phy_device *phydev);
+void phy_package_unlock(struct phy_device *phydev);
+int __phy_package_read(struct phy_device *phydev, unsigned int addr_offset,
+		       u32 regnum);
+int __phy_package_write(struct phy_device *phydev, unsigned int addr_offset,
+			u32 regnum, u16 val);
+int __phy_package_read_mmd(struct phy_device *phydev,
+			   unsigned int addr_offset, int devad,
+			   u32 regnum);
+int __phy_package_write_mmd(struct phy_device *phydev,
+			    unsigned int addr_offset, int devad,
+			    u32 regnum, u16 val);
+bool phy_package_init_once(struct phy_device *phydev);
+bool phy_package_probe_once(struct phy_device *phydev);
+int phy_package_join(struct phy_device *phydev, int base_addr, size_t priv_size);
+int of_phy_package_join(struct phy_device *phydev, size_t priv_size);
+void phy_package_leave(struct phy_device *phydev);
+int devm_phy_package_join(struct device *dev, struct phy_device *phydev,
+			  int base_addr, size_t priv_size);
+int devm_of_phy_package_join(struct device *dev, struct phy_device *phydev,
+			     size_t priv_size);
+int mmd_phy_read(struct mii_bus *bus, int phy_addr, bool is_c45,
+		 int devad, u32 regnum);
+int mmd_phy_write(struct mii_bus *bus, int phy_addr, bool is_c45,
+		  int devad, u32 regnum, u16 val);
+
+#endif /* __PHYLIB_H */