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, 202 insertions, 0 deletions

diff --git a/arch/nios2/lib/memcpy.c b/arch/nios2/lib/memcpy.c
new file mode 100644
index 000000000..1715f5d28
--- /dev/null
+++ b/arch/nios2/lib/memcpy.c
@@ -0,0 +1,202 @@
+/* Extracted from GLIBC memcpy.c and memcopy.h, which is:
+   Copyright (C) 1991, 1992, 1993, 1997, 2004 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Torbjorn Granlund (tege@sics.se).
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <linux/types.h>
+
+/* Type to use for aligned memory operations.
+   This should normally be the biggest type supported by a single load
+   and store.  */
+#define	op_t	unsigned long int
+#define OPSIZ	(sizeof(op_t))
+
+/* Optimal type for storing bytes in registers.  */
+#define	reg_char	char
+
+#define MERGE(w0, sh_1, w1, sh_2) (((w0) >> (sh_1)) | ((w1) << (sh_2)))
+
+/* Copy exactly NBYTES bytes from SRC_BP to DST_BP,
+   without any assumptions about alignment of the pointers.  */
+#define BYTE_COPY_FWD(dst_bp, src_bp, nbytes)				\
+do {									\
+	size_t __nbytes = (nbytes);					\
+	while (__nbytes > 0) {						\
+		unsigned char __x = ((unsigned char *) src_bp)[0];	\
+		src_bp += 1;						\
+		__nbytes -= 1;						\
+		((unsigned char *) dst_bp)[0] = __x;			\
+		dst_bp += 1;						\
+	}								\
+} while (0)
+
+/* Copy *up to* NBYTES bytes from SRC_BP to DST_BP, with
+   the assumption that DST_BP is aligned on an OPSIZ multiple.  If
+   not all bytes could be easily copied, store remaining number of bytes
+   in NBYTES_LEFT, otherwise store 0.  */
+/* extern void _wordcopy_fwd_aligned __P ((long int, long int, size_t)); */
+/* extern void _wordcopy_fwd_dest_aligned __P ((long int, long int, size_t)); */
+#define WORD_COPY_FWD(dst_bp, src_bp, nbytes_left, nbytes)		\
+do {									\
+	if (src_bp % OPSIZ == 0)					\
+		_wordcopy_fwd_aligned(dst_bp, src_bp, (nbytes) / OPSIZ);\
+	else								\
+		_wordcopy_fwd_dest_aligned(dst_bp, src_bp, (nbytes) / OPSIZ);\
+	src_bp += (nbytes) & -OPSIZ;					\
+	dst_bp += (nbytes) & -OPSIZ;					\
+	(nbytes_left) = (nbytes) % OPSIZ;				\
+} while (0)
+
+
+/* Threshold value for when to enter the unrolled loops.  */
+#define	OP_T_THRES	16
+
+/* _wordcopy_fwd_aligned -- Copy block beginning at SRCP to
+   block beginning at DSTP with LEN `op_t' words (not LEN bytes!).
+   Both SRCP and DSTP should be aligned for memory operations on `op_t's.  */
+/* stream-lined (read x8 + write x8) */
+static void _wordcopy_fwd_aligned(long int dstp, long int srcp, size_t len)
+{
+	while (len > 7) {
+		register op_t a0, a1, a2, a3, a4, a5, a6, a7;
+
+		a0 = ((op_t *) srcp)[0];
+		a1 = ((op_t *) srcp)[1];
+		a2 = ((op_t *) srcp)[2];
+		a3 = ((op_t *) srcp)[3];
+		a4 = ((op_t *) srcp)[4];
+		a5 = ((op_t *) srcp)[5];
+		a6 = ((op_t *) srcp)[6];
+		a7 = ((op_t *) srcp)[7];
+		((op_t *) dstp)[0] = a0;
+		((op_t *) dstp)[1] = a1;
+		((op_t *) dstp)[2] = a2;
+		((op_t *) dstp)[3] = a3;
+		((op_t *) dstp)[4] = a4;
+		((op_t *) dstp)[5] = a5;
+		((op_t *) dstp)[6] = a6;
+		((op_t *) dstp)[7] = a7;
+
+		srcp += 8 * OPSIZ;
+		dstp += 8 * OPSIZ;
+		len -= 8;
+	}
+	while (len > 0) {
+		*(op_t *)dstp = *(op_t *)srcp;
+
+		srcp += OPSIZ;
+		dstp += OPSIZ;
+		len -= 1;
+	}
+}
+
+/* _wordcopy_fwd_dest_aligned -- Copy block beginning at SRCP to
+   block beginning at DSTP with LEN `op_t' words (not LEN bytes!).
+   DSTP should be aligned for memory operations on `op_t's, but SRCP must
+   *not* be aligned.  */
+/* stream-lined (read x4 + write x4) */
+static void _wordcopy_fwd_dest_aligned(long int dstp, long int srcp,
+					size_t len)
+{
+	op_t ap;
+	int sh_1, sh_2;
+
+	/* Calculate how to shift a word read at the memory operation
+	aligned srcp to make it aligned for copy. */
+
+	sh_1 = 8 * (srcp % OPSIZ);
+	sh_2 = 8 * OPSIZ - sh_1;
+
+	/* Make SRCP aligned by rounding it down to the beginning of the `op_t'
+	it points in the middle of. */
+	srcp &= -OPSIZ;
+	ap = ((op_t *) srcp)[0];
+	srcp += OPSIZ;
+
+	while (len > 3) {
+		op_t a0, a1, a2, a3;
+
+		a0 = ((op_t *) srcp)[0];
+		a1 = ((op_t *) srcp)[1];
+		a2 = ((op_t *) srcp)[2];
+		a3 = ((op_t *) srcp)[3];
+		((op_t *) dstp)[0] = MERGE(ap, sh_1, a0, sh_2);
+		((op_t *) dstp)[1] = MERGE(a0, sh_1, a1, sh_2);
+		((op_t *) dstp)[2] = MERGE(a1, sh_1, a2, sh_2);
+		((op_t *) dstp)[3] = MERGE(a2, sh_1, a3, sh_2);
+
+		ap = a3;
+		srcp += 4 * OPSIZ;
+		dstp += 4 * OPSIZ;
+		len -= 4;
+	}
+	while (len > 0) {
+		register op_t a0;
+
+		a0 = ((op_t *) srcp)[0];
+		((op_t *) dstp)[0] = MERGE(ap, sh_1, a0, sh_2);
+
+		ap = a0;
+		srcp += OPSIZ;
+		dstp += OPSIZ;
+		len -= 1;
+	}
+}
+
+void *memcpy(void *dstpp, const void *srcpp, size_t len)
+{
+	unsigned long int dstp = (long int) dstpp;
+	unsigned long int srcp = (long int) srcpp;
+
+	/* Copy from the beginning to the end.  */
+
+	/* If there not too few bytes to copy, use word copy.  */
+	if (len >= OP_T_THRES) {
+		/* Copy just a few bytes to make DSTP aligned.  */
+		len -= (-dstp) % OPSIZ;
+		BYTE_COPY_FWD(dstp, srcp, (-dstp) % OPSIZ);
+
+		/* Copy whole pages from SRCP to DSTP by virtual address
+		   manipulation, as much as possible.  */
+
+		/* PAGE_COPY_FWD_MAYBE (dstp, srcp, len, len); */
+
+		/* Copy from SRCP to DSTP taking advantage of the known
+		   alignment of DSTP. Number of bytes remaining is put in the
+		   third argument, i.e. in LEN.  This number may vary from
+		   machine to machine. */
+
+		WORD_COPY_FWD(dstp, srcp, len, len);
+
+		/* Fall out and copy the tail. */
+	}
+
+	/* There are just a few bytes to copy.  Use byte memory operations. */
+	BYTE_COPY_FWD(dstp, srcp, len);
+
+	return dstpp;
+}
+
+void *memcpyb(void *dstpp, const void *srcpp, unsigned len)
+{
+	unsigned long int dstp = (long int) dstpp;
+	unsigned long int srcp = (long int) srcpp;
+
+	BYTE_COPY_FWD(dstp, srcp, len);
+
+	return dstpp;
+}