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, 197 insertions, 0 deletions

diff --git a/arch/sparc/lib/memset.S b/arch/sparc/lib/memset.S
new file mode 100644
index 000000000..a33419dbb
--- /dev/null
+++ b/arch/sparc/lib/memset.S
@@ -0,0 +1,197 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* linux/arch/sparc/lib/memset.S: Sparc optimized memset, bzero and clear_user code
+ * Copyright (C) 1991,1996 Free Software Foundation
+ * Copyright (C) 1996,1997 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
+ * Copyright (C) 1996 David S. Miller (davem@caip.rutgers.edu)
+ *
+ * Calls to memset returns initial %o0. Calls to bzero returns 0, if ok, and
+ * number of bytes not yet set if exception occurs and we were called as
+ * clear_user.
+ */
+
+#include <linux/export.h>
+#include <asm/ptrace.h>
+
+/* Work around cpp -rob */
+#define ALLOC #alloc
+#define EXECINSTR #execinstr
+#define EX(x,y,a,b) 				\
+98: 	x,y;					\
+	.section .fixup,ALLOC,EXECINSTR;	\
+	.align	4;				\
+99:	retl;					\
+	 a, b, %o0;				\
+	.section __ex_table,ALLOC;		\
+	.align	4;				\
+	.word	98b, 99b;			\
+	.text;					\
+	.align	4
+
+#define STORE(source, base, offset, n)		\
+98: 	std source, [base + offset + n];	\
+	.section .fixup,ALLOC,EXECINSTR;	\
+	.align	4;				\
+99:	ba 30f;					\
+	 sub %o3, n - offset, %o3;		\
+	.section __ex_table,ALLOC;		\
+	.align	4;				\
+	.word	98b, 99b;			\
+	.text;					\
+	.align	4;
+
+#define STORE_LAST(source, base, offset, n)	\
+	EX(std source, [base - offset - n],	\
+	   add %o1, offset + n);
+
+/* Please don't change these macros, unless you change the logic
+ * in the .fixup section below as well.
+ * Store 64 bytes at (BASE + OFFSET) using value SOURCE. */
+#define ZERO_BIG_BLOCK(base, offset, source)	\
+	STORE(source, base, offset, 0x00);	\
+	STORE(source, base, offset, 0x08);	\
+	STORE(source, base, offset, 0x10);	\
+	STORE(source, base, offset, 0x18);	\
+	STORE(source, base, offset, 0x20);	\
+	STORE(source, base, offset, 0x28);	\
+	STORE(source, base, offset, 0x30);	\
+	STORE(source, base, offset, 0x38);
+
+#define ZERO_LAST_BLOCKS(base, offset, source)	\
+	STORE_LAST(source, base, offset, 0x38);	\
+	STORE_LAST(source, base, offset, 0x30); \
+	STORE_LAST(source, base, offset, 0x28);	\
+	STORE_LAST(source, base, offset, 0x20);	\
+	STORE_LAST(source, base, offset, 0x18);	\
+	STORE_LAST(source, base, offset, 0x10);	\
+	STORE_LAST(source, base, offset, 0x08);	\
+	STORE_LAST(source, base, offset, 0x00);
+
+	.text
+	.align 4
+
+        .globl  __bzero_begin
+__bzero_begin:
+
+	.globl	__bzero
+	.type	__bzero,#function
+	.globl	memset
+	EXPORT_SYMBOL(__bzero)
+	EXPORT_SYMBOL(memset)
+memset:
+	mov	%o0, %g1
+	mov	1, %g4
+	and	%o1, 0xff, %g3
+	sll	%g3, 8, %g2
+	or	%g3, %g2, %g3
+	sll	%g3, 16, %g2
+	or	%g3, %g2, %g3
+	b	1f
+	 mov	%o2, %o1
+3:
+	cmp	%o2, 3
+	be	2f
+	 EX(stb	%g3, [%o0], sub %o1, 0)
+
+	cmp	%o2, 2
+	be	2f
+	 EX(stb	%g3, [%o0 + 0x01], sub %o1, 1)
+
+	EX(stb	%g3, [%o0 + 0x02], sub %o1, 2)
+2:
+	sub	%o2, 4, %o2
+	add	%o1, %o2, %o1
+	b	4f
+	 sub	%o0, %o2, %o0
+
+__bzero:
+	clr	%g4
+	mov	%g0, %g3
+1:
+	cmp	%o1, 7
+	bleu	7f
+	 andcc	%o0, 3, %o2
+
+	bne	3b
+4:
+	 andcc	%o0, 4, %g0
+
+	be	2f
+	 mov	%g3, %g2
+
+	EX(st	%g3, [%o0], sub %o1, 0)
+	sub	%o1, 4, %o1
+	add	%o0, 4, %o0
+2:
+	andcc	%o1, 0xffffff80, %o3	! Now everything is 8 aligned and o1 is len to run
+	be	9f
+	 andcc	%o1, 0x78, %o2
+10:
+	ZERO_BIG_BLOCK(%o0, 0x00, %g2)
+	subcc	%o3, 128, %o3
+	ZERO_BIG_BLOCK(%o0, 0x40, %g2)
+	bne	10b
+	 add	%o0, 128, %o0
+
+	orcc	%o2, %g0, %g0
+9:
+	be	13f
+	 andcc	%o1, 7, %o1
+
+	srl	%o2, 1, %o3
+	set	13f, %o4
+	sub	%o4, %o3, %o4
+	jmp	%o4
+	 add	%o0, %o2, %o0
+
+	ZERO_LAST_BLOCKS(%o0, 0x48, %g2)
+	ZERO_LAST_BLOCKS(%o0, 0x08, %g2)
+13:
+	be	8f
+	 andcc	%o1, 4, %g0
+
+	be	1f
+	 andcc	%o1, 2, %g0
+
+	EX(st	%g3, [%o0], and %o1, 7)
+	add	%o0, 4, %o0
+1:
+	be	1f
+	 andcc	%o1, 1, %g0
+
+	EX(sth	%g3, [%o0], and %o1, 3)
+	add	%o0, 2, %o0
+1:
+	bne,a	8f
+	 EX(stb	%g3, [%o0], and %o1, 1)
+8:
+	b	0f
+	 nop
+7:
+	be	13b
+	 orcc	%o1, 0, %g0
+
+	be	0f
+8:
+	 add	%o0, 1, %o0
+	subcc	%o1, 1, %o1
+	bne	8b
+	 EX(stb	%g3, [%o0 - 1], add %o1, 1)
+0:
+	andcc	%g4, 1, %g0
+	be	5f
+	 nop
+	retl
+	 mov	%g1, %o0
+5:
+	retl
+	 clr	%o0
+
+	.section .fixup,#alloc,#execinstr
+	.align	4
+30:
+	and	%o1, 0x7f, %o1
+	retl
+	 add	%o3, %o1, %o0
+
+	.globl __bzero_end
+__bzero_end: