From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions 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) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- drivers/rpmsg/rpmsg_ns.c | 124 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 124 insertions(+) create mode 100644 drivers/rpmsg/rpmsg_ns.c (limited to 'drivers/rpmsg/rpmsg_ns.c') diff --git a/drivers/rpmsg/rpmsg_ns.c b/drivers/rpmsg/rpmsg_ns.c new file mode 100644 index 000000000..bde8c8d43 --- /dev/null +++ b/drivers/rpmsg/rpmsg_ns.c @@ -0,0 +1,124 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) STMicroelectronics 2020 - All Rights Reserved + */ +#include +#include +#include +#include +#include +#include + +#include "rpmsg_internal.h" + +/** + * rpmsg_ns_register_device() - register name service device based on rpdev + * @rpdev: prepared rpdev to be used for creating endpoints + * + * This function wraps rpmsg_register_device() preparing the rpdev for use as + * basis for the rpmsg name service device. + */ +int rpmsg_ns_register_device(struct rpmsg_device *rpdev) +{ + rpdev->src = RPMSG_NS_ADDR; + rpdev->dst = RPMSG_NS_ADDR; + + return rpmsg_register_device_override(rpdev, "rpmsg_ns"); +} +EXPORT_SYMBOL(rpmsg_ns_register_device); + +/* invoked when a name service announcement arrives */ +static int rpmsg_ns_cb(struct rpmsg_device *rpdev, void *data, int len, + void *priv, u32 src) +{ + struct rpmsg_ns_msg *msg = data; + struct rpmsg_device *newch; + struct rpmsg_channel_info chinfo; + struct device *dev = rpdev->dev.parent; + int ret; + +#if defined(CONFIG_DYNAMIC_DEBUG) + dynamic_hex_dump("NS announcement: ", DUMP_PREFIX_NONE, 16, 1, + data, len, true); +#endif + + if (len != sizeof(*msg)) { + dev_err(dev, "malformed ns msg (%d)\n", len); + return -EINVAL; + } + + /* don't trust the remote processor for null terminating the name */ + msg->name[RPMSG_NAME_SIZE - 1] = '\0'; + + strscpy_pad(chinfo.name, msg->name, sizeof(chinfo.name)); + chinfo.src = RPMSG_ADDR_ANY; + chinfo.dst = rpmsg32_to_cpu(rpdev, msg->addr); + + dev_info(dev, "%sing channel %s addr 0x%x\n", + rpmsg32_to_cpu(rpdev, msg->flags) & RPMSG_NS_DESTROY ? + "destroy" : "creat", msg->name, chinfo.dst); + + if (rpmsg32_to_cpu(rpdev, msg->flags) & RPMSG_NS_DESTROY) { + ret = rpmsg_release_channel(rpdev, &chinfo); + if (ret) + dev_err(dev, "rpmsg_destroy_channel failed: %d\n", ret); + } else { + newch = rpmsg_create_channel(rpdev, &chinfo); + if (!newch) + dev_err(dev, "rpmsg_create_channel failed\n"); + } + + return 0; +} + +static int rpmsg_ns_probe(struct rpmsg_device *rpdev) +{ + struct rpmsg_endpoint *ns_ept; + struct rpmsg_channel_info ns_chinfo = { + .src = RPMSG_NS_ADDR, + .dst = RPMSG_NS_ADDR, + .name = "name_service", + }; + + /* + * Create the NS announcement service endpoint associated to the RPMsg + * device. The endpoint will be automatically destroyed when the RPMsg + * device will be deleted. + */ + ns_ept = rpmsg_create_ept(rpdev, rpmsg_ns_cb, NULL, ns_chinfo); + if (!ns_ept) { + dev_err(&rpdev->dev, "failed to create the ns ept\n"); + return -ENOMEM; + } + rpdev->ept = ns_ept; + + return 0; +} + +static struct rpmsg_driver rpmsg_ns_driver = { + .drv.name = KBUILD_MODNAME, + .probe = rpmsg_ns_probe, +}; + +static int rpmsg_ns_init(void) +{ + int ret; + + ret = register_rpmsg_driver(&rpmsg_ns_driver); + if (ret < 0) + pr_err("%s: Failed to register rpmsg driver\n", __func__); + + return ret; +} +postcore_initcall(rpmsg_ns_init); + +static void rpmsg_ns_exit(void) +{ + unregister_rpmsg_driver(&rpmsg_ns_driver); +} +module_exit(rpmsg_ns_exit); + +MODULE_DESCRIPTION("Name service announcement rpmsg driver"); +MODULE_AUTHOR("Arnaud Pouliquen "); +MODULE_ALIAS("rpmsg:" KBUILD_MODNAME); +MODULE_LICENSE("GPL v2"); -- cgit v1.3.1