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, 306 insertions, 0 deletions

diff --git a/net/bluetooth/selftest.c b/net/bluetooth/selftest.c
new file mode 100644
index 000000000..ae5b44bb9
--- /dev/null
+++ b/net/bluetooth/selftest.c
@@ -0,0 +1,306 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+   BlueZ - Bluetooth protocol stack for Linux
+
+   Copyright (C) 2014 Intel Corporation
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+   OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.
+   IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) AND AUTHOR(S) BE LIABLE FOR ANY
+   CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES
+   WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+   ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+   ALL LIABILITY, INCLUDING LIABILITY FOR INFRINGEMENT OF ANY PATENTS,
+   COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS, RELATING TO USE OF THIS
+   SOFTWARE IS DISCLAIMED.
+*/
+
+#include <linux/debugfs.h>
+
+#include <net/bluetooth/bluetooth.h>
+#include <net/bluetooth/hci_core.h>
+
+#include "ecdh_helper.h"
+#include "smp.h"
+#include "selftest.h"
+
+#if IS_ENABLED(CONFIG_BT_SELFTEST_ECDH)
+
+static const u8 priv_a_1[32] __initconst = {
+	0xbd, 0x1a, 0x3c, 0xcd, 0xa6, 0xb8, 0x99, 0x58,
+	0x99, 0xb7, 0x40, 0xeb, 0x7b, 0x60, 0xff, 0x4a,
+	0x50, 0x3f, 0x10, 0xd2, 0xe3, 0xb3, 0xc9, 0x74,
+	0x38, 0x5f, 0xc5, 0xa3, 0xd4, 0xf6, 0x49, 0x3f,
+};
+static const u8 priv_b_1[32] __initconst = {
+	0xfd, 0xc5, 0x7f, 0xf4, 0x49, 0xdd, 0x4f, 0x6b,
+	0xfb, 0x7c, 0x9d, 0xf1, 0xc2, 0x9a, 0xcb, 0x59,
+	0x2a, 0xe7, 0xd4, 0xee, 0xfb, 0xfc, 0x0a, 0x90,
+	0x9a, 0xbb, 0xf6, 0x32, 0x3d, 0x8b, 0x18, 0x55,
+};
+static const u8 pub_a_1[64] __initconst = {
+	0xe6, 0x9d, 0x35, 0x0e, 0x48, 0x01, 0x03, 0xcc,
+	0xdb, 0xfd, 0xf4, 0xac, 0x11, 0x91, 0xf4, 0xef,
+	0xb9, 0xa5, 0xf9, 0xe9, 0xa7, 0x83, 0x2c, 0x5e,
+	0x2c, 0xbe, 0x97, 0xf2, 0xd2, 0x03, 0xb0, 0x20,
+
+	0x8b, 0xd2, 0x89, 0x15, 0xd0, 0x8e, 0x1c, 0x74,
+	0x24, 0x30, 0xed, 0x8f, 0xc2, 0x45, 0x63, 0x76,
+	0x5c, 0x15, 0x52, 0x5a, 0xbf, 0x9a, 0x32, 0x63,
+	0x6d, 0xeb, 0x2a, 0x65, 0x49, 0x9c, 0x80, 0xdc,
+};
+static const u8 pub_b_1[64] __initconst = {
+	0x90, 0xa1, 0xaa, 0x2f, 0xb2, 0x77, 0x90, 0x55,
+	0x9f, 0xa6, 0x15, 0x86, 0xfd, 0x8a, 0xb5, 0x47,
+	0x00, 0x4c, 0x9e, 0xf1, 0x84, 0x22, 0x59, 0x09,
+	0x96, 0x1d, 0xaf, 0x1f, 0xf0, 0xf0, 0xa1, 0x1e,
+
+	0x4a, 0x21, 0xb1, 0x15, 0xf9, 0xaf, 0x89, 0x5f,
+	0x76, 0x36, 0x8e, 0xe2, 0x30, 0x11, 0x2d, 0x47,
+	0x60, 0x51, 0xb8, 0x9a, 0x3a, 0x70, 0x56, 0x73,
+	0x37, 0xad, 0x9d, 0x42, 0x3e, 0xf3, 0x55, 0x4c,
+};
+static const u8 dhkey_1[32] __initconst = {
+	0x98, 0xa6, 0xbf, 0x73, 0xf3, 0x34, 0x8d, 0x86,
+	0xf1, 0x66, 0xf8, 0xb4, 0x13, 0x6b, 0x79, 0x99,
+	0x9b, 0x7d, 0x39, 0x0a, 0xa6, 0x10, 0x10, 0x34,
+	0x05, 0xad, 0xc8, 0x57, 0xa3, 0x34, 0x02, 0xec,
+};
+
+static const u8 priv_a_2[32] __initconst = {
+	0x63, 0x76, 0x45, 0xd0, 0xf7, 0x73, 0xac, 0xb7,
+	0xff, 0xdd, 0x03, 0x72, 0xb9, 0x72, 0x85, 0xb4,
+	0x41, 0xb6, 0x5d, 0x0c, 0x5d, 0x54, 0x84, 0x60,
+	0x1a, 0xa3, 0x9a, 0x3c, 0x69, 0x16, 0xa5, 0x06,
+};
+static const u8 priv_b_2[32] __initconst = {
+	0xba, 0x30, 0x55, 0x50, 0x19, 0xa2, 0xca, 0xa3,
+	0xa5, 0x29, 0x08, 0xc6, 0xb5, 0x03, 0x88, 0x7e,
+	0x03, 0x2b, 0x50, 0x73, 0xd4, 0x2e, 0x50, 0x97,
+	0x64, 0xcd, 0x72, 0x0d, 0x67, 0xa0, 0x9a, 0x52,
+};
+static const u8 pub_a_2[64] __initconst = {
+	0xdd, 0x78, 0x5c, 0x74, 0x03, 0x9b, 0x7e, 0x98,
+	0xcb, 0x94, 0x87, 0x4a, 0xad, 0xfa, 0xf8, 0xd5,
+	0x43, 0x3e, 0x5c, 0xaf, 0xea, 0xb5, 0x4c, 0xf4,
+	0x9e, 0x80, 0x79, 0x57, 0x7b, 0xa4, 0x31, 0x2c,
+
+	0x4f, 0x5d, 0x71, 0x43, 0x77, 0x43, 0xf8, 0xea,
+	0xd4, 0x3e, 0xbd, 0x17, 0x91, 0x10, 0x21, 0xd0,
+	0x1f, 0x87, 0x43, 0x8e, 0x40, 0xe2, 0x52, 0xcd,
+	0xbe, 0xdf, 0x98, 0x38, 0x18, 0x12, 0x95, 0x91,
+};
+static const u8 pub_b_2[64] __initconst = {
+	0xcc, 0x00, 0x65, 0xe1, 0xf5, 0x6c, 0x0d, 0xcf,
+	0xec, 0x96, 0x47, 0x20, 0x66, 0xc9, 0xdb, 0x84,
+	0x81, 0x75, 0xa8, 0x4d, 0xc0, 0xdf, 0xc7, 0x9d,
+	0x1b, 0x3f, 0x3d, 0xf2, 0x3f, 0xe4, 0x65, 0xf4,
+
+	0x79, 0xb2, 0xec, 0xd8, 0xca, 0x55, 0xa1, 0xa8,
+	0x43, 0x4d, 0x6b, 0xca, 0x10, 0xb0, 0xc2, 0x01,
+	0xc2, 0x33, 0x4e, 0x16, 0x24, 0xc4, 0xef, 0xee,
+	0x99, 0xd8, 0xbb, 0xbc, 0x48, 0xd0, 0x01, 0x02,
+};
+static const u8 dhkey_2[32] __initconst = {
+	0x69, 0xeb, 0x21, 0x32, 0xf2, 0xc6, 0x05, 0x41,
+	0x60, 0x19, 0xcd, 0x5e, 0x94, 0xe1, 0xe6, 0x5f,
+	0x33, 0x07, 0xe3, 0x38, 0x4b, 0x68, 0xe5, 0x62,
+	0x3f, 0x88, 0x6d, 0x2f, 0x3a, 0x84, 0x85, 0xab,
+};
+
+static const u8 priv_a_3[32] __initconst = {
+	0xbd, 0x1a, 0x3c, 0xcd, 0xa6, 0xb8, 0x99, 0x58,
+	0x99, 0xb7, 0x40, 0xeb, 0x7b, 0x60, 0xff, 0x4a,
+	0x50, 0x3f, 0x10, 0xd2, 0xe3, 0xb3, 0xc9, 0x74,
+	0x38, 0x5f, 0xc5, 0xa3, 0xd4, 0xf6, 0x49, 0x3f,
+};
+static const u8 pub_a_3[64] __initconst = {
+	0xe6, 0x9d, 0x35, 0x0e, 0x48, 0x01, 0x03, 0xcc,
+	0xdb, 0xfd, 0xf4, 0xac, 0x11, 0x91, 0xf4, 0xef,
+	0xb9, 0xa5, 0xf9, 0xe9, 0xa7, 0x83, 0x2c, 0x5e,
+	0x2c, 0xbe, 0x97, 0xf2, 0xd2, 0x03, 0xb0, 0x20,
+
+	0x8b, 0xd2, 0x89, 0x15, 0xd0, 0x8e, 0x1c, 0x74,
+	0x24, 0x30, 0xed, 0x8f, 0xc2, 0x45, 0x63, 0x76,
+	0x5c, 0x15, 0x52, 0x5a, 0xbf, 0x9a, 0x32, 0x63,
+	0x6d, 0xeb, 0x2a, 0x65, 0x49, 0x9c, 0x80, 0xdc,
+};
+static const u8 dhkey_3[32] __initconst = {
+	0x2d, 0xab, 0x00, 0x48, 0xcb, 0xb3, 0x7b, 0xda,
+	0x55, 0x7b, 0x8b, 0x72, 0xa8, 0x57, 0x87, 0xc3,
+	0x87, 0x27, 0x99, 0x32, 0xfc, 0x79, 0x5f, 0xae,
+	0x7c, 0x1c, 0xf9, 0x49, 0xe6, 0xd7, 0xaa, 0x70,
+};
+
+static int __init test_ecdh_sample(struct crypto_kpp *tfm, const u8 priv_a[32],
+				   const u8 priv_b[32], const u8 pub_a[64],
+				   const u8 pub_b[64], const u8 dhkey[32])
+{
+	u8 *tmp, *dhkey_a, *dhkey_b;
+	int ret;
+
+	tmp = kmalloc(64, GFP_KERNEL);
+	if (!tmp)
+		return -EINVAL;
+
+	dhkey_a = &tmp[0];
+	dhkey_b = &tmp[32];
+
+	ret = set_ecdh_privkey(tfm, priv_a);
+	if (ret)
+		goto out;
+
+	ret = compute_ecdh_secret(tfm, pub_b, dhkey_a);
+	if (ret)
+		goto out;
+
+	if (memcmp(dhkey_a, dhkey, 32)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	ret = set_ecdh_privkey(tfm, priv_b);
+	if (ret)
+		goto out;
+
+	ret = compute_ecdh_secret(tfm, pub_a, dhkey_b);
+	if (ret)
+		goto out;
+
+	if (memcmp(dhkey_b, dhkey, 32))
+		ret = -EINVAL;
+	/* fall through*/
+out:
+	kfree(tmp);
+	return ret;
+}
+
+static char test_ecdh_buffer[32];
+
+static ssize_t test_ecdh_read(struct file *file, char __user *user_buf,
+			      size_t count, loff_t *ppos)
+{
+	return simple_read_from_buffer(user_buf, count, ppos, test_ecdh_buffer,
+				       strlen(test_ecdh_buffer));
+}
+
+static const struct file_operations test_ecdh_fops = {
+	.open		= simple_open,
+	.read		= test_ecdh_read,
+	.llseek		= default_llseek,
+};
+
+static int __init test_ecdh(void)
+{
+	struct crypto_kpp *tfm;
+	ktime_t calltime, delta, rettime;
+	unsigned long long duration = 0;
+	int err;
+
+	calltime = ktime_get();
+
+	tfm = crypto_alloc_kpp("ecdh-nist-p256", 0, 0);
+	if (IS_ERR(tfm)) {
+		BT_ERR("Unable to create ECDH crypto context");
+		err = PTR_ERR(tfm);
+		goto done;
+	}
+
+	err = test_ecdh_sample(tfm, priv_a_1, priv_b_1, pub_a_1, pub_b_1,
+			       dhkey_1);
+	if (err) {
+		BT_ERR("ECDH sample 1 failed");
+		goto done;
+	}
+
+	err = test_ecdh_sample(tfm, priv_a_2, priv_b_2, pub_a_2, pub_b_2,
+			       dhkey_2);
+	if (err) {
+		BT_ERR("ECDH sample 2 failed");
+		goto done;
+	}
+
+	err = test_ecdh_sample(tfm, priv_a_3, priv_a_3, pub_a_3, pub_a_3,
+			       dhkey_3);
+	if (err) {
+		BT_ERR("ECDH sample 3 failed");
+		goto done;
+	}
+
+	crypto_free_kpp(tfm);
+
+	rettime = ktime_get();
+	delta = ktime_sub(rettime, calltime);
+	duration = (unsigned long long) ktime_to_ns(delta) >> 10;
+
+	BT_INFO("ECDH test passed in %llu usecs", duration);
+
+done:
+	if (!err)
+		snprintf(test_ecdh_buffer, sizeof(test_ecdh_buffer),
+			 "PASS (%llu usecs)\n", duration);
+	else
+		snprintf(test_ecdh_buffer, sizeof(test_ecdh_buffer), "FAIL\n");
+
+	debugfs_create_file("selftest_ecdh", 0444, bt_debugfs, NULL,
+			    &test_ecdh_fops);
+
+	return err;
+}
+
+#else
+
+static inline int test_ecdh(void)
+{
+	return 0;
+}
+
+#endif
+
+static int __init run_selftest(void)
+{
+	int err;
+
+	BT_INFO("Starting self testing");
+
+	err = test_ecdh();
+	if (err)
+		goto done;
+
+	err = bt_selftest_smp();
+
+done:
+	BT_INFO("Finished self testing");
+
+	return err;
+}
+
+#if IS_MODULE(CONFIG_BT)
+
+/* This is run when CONFIG_BT_SELFTEST=y and CONFIG_BT=m and is just a
+ * wrapper to allow running this at module init.
+ *
+ * If CONFIG_BT_SELFTEST=n, then this code is not compiled at all.
+ */
+int __init bt_selftest(void)
+{
+	return run_selftest();
+}
+
+#else
+
+/* This is run when CONFIG_BT_SELFTEST=y and CONFIG_BT=y and is run
+ * via late_initcall() as last item in the initialization sequence.
+ *
+ * If CONFIG_BT_SELFTEST=n, then this code is not compiled at all.
+ */
+static int __init bt_selftest_init(void)
+{
+	return run_selftest();
+}
+late_initcall(bt_selftest_init);
+
+#endif