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, 291 insertions, 0 deletions

diff --git a/lib/crypto/gf128mul.c b/lib/crypto/gf128mul.c
new file mode 100644
index 000000000..7ebf07ce1
--- /dev/null
+++ b/lib/crypto/gf128mul.c
@@ -0,0 +1,291 @@
+/* gf128mul.c - GF(2^128) multiplication functions
+ *
+ * Copyright (c) 2003, Dr Brian Gladman, Worcester, UK.
+ * Copyright (c) 2006, Rik Snel <rsnel@cube.dyndns.org>
+ *
+ * Based on Dr Brian Gladman's (GPL'd) work published at
+ * http://gladman.plushost.co.uk/oldsite/cryptography_technology/index.php
+ * See the original copyright notice below.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ */
+
+/*
+ ---------------------------------------------------------------------------
+ Copyright (c) 2003, Dr Brian Gladman, Worcester, UK.   All rights reserved.
+
+ LICENSE TERMS
+
+ The free distribution and use of this software in both source and binary
+ form is allowed (with or without changes) provided that:
+
+   1. distributions of this source code include the above copyright
+      notice, this list of conditions and the following disclaimer;
+
+   2. distributions in binary form include the above copyright
+      notice, this list of conditions and the following disclaimer
+      in the documentation and/or other associated materials;
+
+   3. the copyright holder's name is not used to endorse products
+      built using this software without specific written permission.
+
+ ALTERNATIVELY, provided that this notice is retained in full, this product
+ may be distributed under the terms of the GNU General Public License (GPL),
+ in which case the provisions of the GPL apply INSTEAD OF those given above.
+
+ DISCLAIMER
+
+ This software is provided 'as is' with no explicit or implied warranties
+ in respect of its properties, including, but not limited to, correctness
+ and/or fitness for purpose.
+ ---------------------------------------------------------------------------
+ Issue 31/01/2006
+
+ This file provides fast multiplication in GF(2^128) as required by several
+ cryptographic authentication modes
+*/
+
+#include <crypto/gf128mul.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+#define gf128mul_dat(q) { \
+	q(0x00), q(0x01), q(0x02), q(0x03), q(0x04), q(0x05), q(0x06), q(0x07),\
+	q(0x08), q(0x09), q(0x0a), q(0x0b), q(0x0c), q(0x0d), q(0x0e), q(0x0f),\
+	q(0x10), q(0x11), q(0x12), q(0x13), q(0x14), q(0x15), q(0x16), q(0x17),\
+	q(0x18), q(0x19), q(0x1a), q(0x1b), q(0x1c), q(0x1d), q(0x1e), q(0x1f),\
+	q(0x20), q(0x21), q(0x22), q(0x23), q(0x24), q(0x25), q(0x26), q(0x27),\
+	q(0x28), q(0x29), q(0x2a), q(0x2b), q(0x2c), q(0x2d), q(0x2e), q(0x2f),\
+	q(0x30), q(0x31), q(0x32), q(0x33), q(0x34), q(0x35), q(0x36), q(0x37),\
+	q(0x38), q(0x39), q(0x3a), q(0x3b), q(0x3c), q(0x3d), q(0x3e), q(0x3f),\
+	q(0x40), q(0x41), q(0x42), q(0x43), q(0x44), q(0x45), q(0x46), q(0x47),\
+	q(0x48), q(0x49), q(0x4a), q(0x4b), q(0x4c), q(0x4d), q(0x4e), q(0x4f),\
+	q(0x50), q(0x51), q(0x52), q(0x53), q(0x54), q(0x55), q(0x56), q(0x57),\
+	q(0x58), q(0x59), q(0x5a), q(0x5b), q(0x5c), q(0x5d), q(0x5e), q(0x5f),\
+	q(0x60), q(0x61), q(0x62), q(0x63), q(0x64), q(0x65), q(0x66), q(0x67),\
+	q(0x68), q(0x69), q(0x6a), q(0x6b), q(0x6c), q(0x6d), q(0x6e), q(0x6f),\
+	q(0x70), q(0x71), q(0x72), q(0x73), q(0x74), q(0x75), q(0x76), q(0x77),\
+	q(0x78), q(0x79), q(0x7a), q(0x7b), q(0x7c), q(0x7d), q(0x7e), q(0x7f),\
+	q(0x80), q(0x81), q(0x82), q(0x83), q(0x84), q(0x85), q(0x86), q(0x87),\
+	q(0x88), q(0x89), q(0x8a), q(0x8b), q(0x8c), q(0x8d), q(0x8e), q(0x8f),\
+	q(0x90), q(0x91), q(0x92), q(0x93), q(0x94), q(0x95), q(0x96), q(0x97),\
+	q(0x98), q(0x99), q(0x9a), q(0x9b), q(0x9c), q(0x9d), q(0x9e), q(0x9f),\
+	q(0xa0), q(0xa1), q(0xa2), q(0xa3), q(0xa4), q(0xa5), q(0xa6), q(0xa7),\
+	q(0xa8), q(0xa9), q(0xaa), q(0xab), q(0xac), q(0xad), q(0xae), q(0xaf),\
+	q(0xb0), q(0xb1), q(0xb2), q(0xb3), q(0xb4), q(0xb5), q(0xb6), q(0xb7),\
+	q(0xb8), q(0xb9), q(0xba), q(0xbb), q(0xbc), q(0xbd), q(0xbe), q(0xbf),\
+	q(0xc0), q(0xc1), q(0xc2), q(0xc3), q(0xc4), q(0xc5), q(0xc6), q(0xc7),\
+	q(0xc8), q(0xc9), q(0xca), q(0xcb), q(0xcc), q(0xcd), q(0xce), q(0xcf),\
+	q(0xd0), q(0xd1), q(0xd2), q(0xd3), q(0xd4), q(0xd5), q(0xd6), q(0xd7),\
+	q(0xd8), q(0xd9), q(0xda), q(0xdb), q(0xdc), q(0xdd), q(0xde), q(0xdf),\
+	q(0xe0), q(0xe1), q(0xe2), q(0xe3), q(0xe4), q(0xe5), q(0xe6), q(0xe7),\
+	q(0xe8), q(0xe9), q(0xea), q(0xeb), q(0xec), q(0xed), q(0xee), q(0xef),\
+	q(0xf0), q(0xf1), q(0xf2), q(0xf3), q(0xf4), q(0xf5), q(0xf6), q(0xf7),\
+	q(0xf8), q(0xf9), q(0xfa), q(0xfb), q(0xfc), q(0xfd), q(0xfe), q(0xff) \
+}
+
+/*
+ * Given a value i in 0..255 as the byte overflow when a field element
+ * in GF(2^128) is multiplied by x^8, the following macro returns the
+ * 16-bit value that must be XOR-ed into the low-degree end of the
+ * product to reduce it modulo the polynomial x^128 + x^7 + x^2 + x + 1.
+ *
+ * There are two versions of the macro, and hence two tables: one for
+ * the "be" convention where the highest-order bit is the coefficient of
+ * the highest-degree polynomial term, and one for the "le" convention
+ * where the highest-order bit is the coefficient of the lowest-degree
+ * polynomial term.  In both cases the values are stored in CPU byte
+ * endianness such that the coefficients are ordered consistently across
+ * bytes, i.e. in the "be" table bits 15..0 of the stored value
+ * correspond to the coefficients of x^15..x^0, and in the "le" table
+ * bits 15..0 correspond to the coefficients of x^0..x^15.
+ *
+ * Therefore, provided that the appropriate byte endianness conversions
+ * are done by the multiplication functions (and these must be in place
+ * anyway to support both little endian and big endian CPUs), the "be"
+ * table can be used for multiplications of both "bbe" and "ble"
+ * elements, and the "le" table can be used for multiplications of both
+ * "lle" and "lbe" elements.
+ */
+
+#define xda_be(i) ( \
+	(i & 0x80 ? 0x4380 : 0) ^ (i & 0x40 ? 0x21c0 : 0) ^ \
+	(i & 0x20 ? 0x10e0 : 0) ^ (i & 0x10 ? 0x0870 : 0) ^ \
+	(i & 0x08 ? 0x0438 : 0) ^ (i & 0x04 ? 0x021c : 0) ^ \
+	(i & 0x02 ? 0x010e : 0) ^ (i & 0x01 ? 0x0087 : 0) \
+)
+
+#define xda_le(i) ( \
+	(i & 0x80 ? 0xe100 : 0) ^ (i & 0x40 ? 0x7080 : 0) ^ \
+	(i & 0x20 ? 0x3840 : 0) ^ (i & 0x10 ? 0x1c20 : 0) ^ \
+	(i & 0x08 ? 0x0e10 : 0) ^ (i & 0x04 ? 0x0708 : 0) ^ \
+	(i & 0x02 ? 0x0384 : 0) ^ (i & 0x01 ? 0x01c2 : 0) \
+)
+
+static const u16 gf128mul_table_be[256] = gf128mul_dat(xda_be);
+
+/* A table-less implementation of multiplying by x^8 */
+static void gf128mul_x8_lle_ti(be128 *x)
+{
+	u64 a = be64_to_cpu(x->a);
+	u64 b = be64_to_cpu(x->b);
+	u64 _tt = xda_le(b & 0xff); /* avoid table lookup */
+
+	x->b = cpu_to_be64((b >> 8) | (a << 56));
+	x->a = cpu_to_be64((a >> 8) ^ (_tt << 48));
+}
+
+static void gf128mul_x8_bbe(be128 *x)
+{
+	u64 a = be64_to_cpu(x->a);
+	u64 b = be64_to_cpu(x->b);
+	u64 _tt = gf128mul_table_be[a >> 56];
+
+	x->a = cpu_to_be64((a << 8) | (b >> 56));
+	x->b = cpu_to_be64((b << 8) ^ _tt);
+}
+
+void gf128mul_x8_ble(le128 *r, const le128 *x)
+{
+	u64 a = le64_to_cpu(x->a);
+	u64 b = le64_to_cpu(x->b);
+	u64 _tt = gf128mul_table_be[a >> 56];
+
+	r->a = cpu_to_le64((a << 8) | (b >> 56));
+	r->b = cpu_to_le64((b << 8) ^ _tt);
+}
+EXPORT_SYMBOL(gf128mul_x8_ble);
+
+void gf128mul_lle(be128 *r, const be128 *b)
+{
+	/*
+	 * The p array should be aligned to twice the size of its element type,
+	 * so that every even/odd pair is guaranteed to share a cacheline
+	 * (assuming a cacheline size of 32 bytes or more, which is by far the
+	 * most common). This ensures that each be128_xor() call in the loop
+	 * takes the same amount of time regardless of the value of 'ch', which
+	 * is derived from function parameter 'b', which is commonly used as a
+	 * key, e.g., for GHASH. The odd array elements are all set to zero,
+	 * making each be128_xor() a NOP if its associated bit in 'ch' is not
+	 * set, and this is equivalent to calling be128_xor() conditionally.
+	 * This approach aims to avoid leaking information about such keys
+	 * through execution time variances.
+	 *
+	 * Unfortunately, __aligned(16) or higher does not work on x86 for
+	 * variables on the stack so we need to perform the alignment by hand.
+	 */
+	be128 array[16 + 3] = {};
+	be128 *p = PTR_ALIGN(&array[0], 2 * sizeof(be128));
+	int i;
+
+	p[0] = *r;
+	for (i = 0; i < 7; ++i)
+		gf128mul_x_lle(&p[2 * i + 2], &p[2 * i]);
+
+	memset(r, 0, sizeof(*r));
+	for (i = 0;;) {
+		u8 ch = ((u8 *)b)[15 - i];
+
+		be128_xor(r, r, &p[ 0 + !(ch & 0x80)]);
+		be128_xor(r, r, &p[ 2 + !(ch & 0x40)]);
+		be128_xor(r, r, &p[ 4 + !(ch & 0x20)]);
+		be128_xor(r, r, &p[ 6 + !(ch & 0x10)]);
+		be128_xor(r, r, &p[ 8 + !(ch & 0x08)]);
+		be128_xor(r, r, &p[10 + !(ch & 0x04)]);
+		be128_xor(r, r, &p[12 + !(ch & 0x02)]);
+		be128_xor(r, r, &p[14 + !(ch & 0x01)]);
+
+		if (++i >= 16)
+			break;
+
+		gf128mul_x8_lle_ti(r); /* use the time invariant version */
+	}
+}
+EXPORT_SYMBOL(gf128mul_lle);
+
+/*      This version uses 64k bytes of table space.
+    A 16 byte buffer has to be multiplied by a 16 byte key
+    value in GF(2^128).  If we consider a GF(2^128) value in
+    the buffer's lowest byte, we can construct a table of
+    the 256 16 byte values that result from the 256 values
+    of this byte.  This requires 4096 bytes. But we also
+    need tables for each of the 16 higher bytes in the
+    buffer as well, which makes 64 kbytes in total.
+*/
+/* additional explanation
+ * t[0][BYTE] contains g*BYTE
+ * t[1][BYTE] contains g*x^8*BYTE
+ *  ..
+ * t[15][BYTE] contains g*x^120*BYTE */
+struct gf128mul_64k *gf128mul_init_64k_bbe(const be128 *g)
+{
+	struct gf128mul_64k *t;
+	int i, j, k;
+
+	t = kzalloc_obj(*t);
+	if (!t)
+		goto out;
+
+	for (i = 0; i < 16; i++) {
+		t->t[i] = kzalloc_obj(*t->t[i]);
+		if (!t->t[i]) {
+			gf128mul_free_64k(t);
+			t = NULL;
+			goto out;
+		}
+	}
+
+	t->t[0]->t[1] = *g;
+	for (j = 1; j <= 64; j <<= 1)
+		gf128mul_x_bbe(&t->t[0]->t[j + j], &t->t[0]->t[j]);
+
+	for (i = 0;;) {
+		for (j = 2; j < 256; j += j)
+			for (k = 1; k < j; ++k)
+				be128_xor(&t->t[i]->t[j + k],
+					  &t->t[i]->t[j], &t->t[i]->t[k]);
+
+		if (++i >= 16)
+			break;
+
+		for (j = 128; j > 0; j >>= 1) {
+			t->t[i]->t[j] = t->t[i - 1]->t[j];
+			gf128mul_x8_bbe(&t->t[i]->t[j]);
+		}
+	}
+
+out:
+	return t;
+}
+EXPORT_SYMBOL(gf128mul_init_64k_bbe);
+
+void gf128mul_free_64k(struct gf128mul_64k *t)
+{
+	int i;
+
+	for (i = 0; i < 16; i++)
+		kfree_sensitive(t->t[i]);
+	kfree_sensitive(t);
+}
+EXPORT_SYMBOL(gf128mul_free_64k);
+
+void gf128mul_64k_bbe(be128 *a, const struct gf128mul_64k *t)
+{
+	u8 *ap = (u8 *)a;
+	be128 r[1];
+	int i;
+
+	*r = t->t[0]->t[ap[15]];
+	for (i = 1; i < 16; ++i)
+		be128_xor(r, r, &t->t[i]->t[ap[15 - i]]);
+	*a = *r;
+}
+EXPORT_SYMBOL(gf128mul_64k_bbe);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Functions for multiplying elements of GF(2^128)");