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/net/netdevsim/psp.c | 289 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 289 insertions(+) create mode 100644 drivers/net/netdevsim/psp.c (limited to 'drivers/net/netdevsim/psp.c') diff --git a/drivers/net/netdevsim/psp.c b/drivers/net/netdevsim/psp.c new file mode 100644 index 000000000..6b3532b5e --- /dev/null +++ b/drivers/net/netdevsim/psp.c @@ -0,0 +1,289 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include +#include +#include + +#include "netdevsim.h" + +void nsim_psp_handle_ext(struct sk_buff *skb, struct skb_ext *psp_ext) +{ + if (psp_ext) + __skb_ext_set(skb, SKB_EXT_PSP, psp_ext); +} + +enum skb_drop_reason +nsim_do_psp(struct sk_buff *skb, struct netdevsim *ns, + struct netdevsim *peer_ns, struct skb_ext **psp_ext) +{ + enum skb_drop_reason rc = 0; + struct psp_dev *peer_psd; + struct psp_assoc *pas; + struct net *net; + int psp_len; + void **ptr; + + rcu_read_lock(); + pas = psp_skb_get_assoc_rcu(skb); + if (!pas) { + rc = SKB_NOT_DROPPED_YET; + goto out_unlock; + } + + if (!skb_transport_header_was_set(skb)) { + rc = SKB_DROP_REASON_PSP_OUTPUT; + goto out_unlock; + } + + ptr = psp_assoc_drv_data(pas); + if (*ptr != ns) { + rc = SKB_DROP_REASON_PSP_OUTPUT; + goto out_unlock; + } + + net = sock_net(skb->sk); + if (!psp_dev_encapsulate(net, skb, pas->tx.spi, pas->version, 0)) { + rc = SKB_DROP_REASON_PSP_OUTPUT; + goto out_unlock; + } + + psp_len = skb->len - skb_inner_transport_offset(skb); + atomic64_inc(&ns->psp.tx_packets); + atomic64_add(psp_len, &ns->psp.tx_bytes); + + /* Now pretend we just received this frame */ + peer_psd = rcu_dereference(peer_ns->psp.dev); + if (peer_psd && peer_psd->config.versions & (1 << pas->version)) { + bool strip_icv = false; + u8 generation; + + /* We cheat a bit and put the generation in the key. + * In real life if generation was too old, then decryption would + * fail. Here, we just make it so a bad key causes a bad + * generation too, and psp_sk_rx_policy_check() will fail. + */ + generation = pas->tx.key[0]; + + skb_ext_reset(skb); + skb->mac_len = ETH_HLEN; + if (psp_dev_rcv(skb, peer_psd->id, generation, strip_icv)) { + rc = SKB_DROP_REASON_PSP_OUTPUT; + goto out_unlock; + } + + *psp_ext = skb->extensions; + refcount_inc(&(*psp_ext)->refcnt); + skb->decrypted = 1; + + atomic64_inc(&peer_ns->psp.rx_packets); + atomic64_add(psp_len, &peer_ns->psp.rx_bytes); + } else { + struct ipv6hdr *ip6h __maybe_unused; + struct iphdr *iph; + struct udphdr *uh; + __wsum csum; + int udplen; + + /* Do not decapsulate. Receive the skb with the udp and psp + * headers still there as if this is a normal udp packet. + * psp_dev_encapsulate() sets udp checksum to 0, so we need to + * provide a valid checksum here, so the skb isn't dropped. + */ + uh = udp_hdr(skb); + udplen = udp_get_len(skb, uh, skb_transport_offset(skb)); + csum = skb_checksum(skb, skb_transport_offset(skb), + udplen, 0); + + switch (skb->protocol) { + case htons(ETH_P_IP): + iph = ip_hdr(skb); + uh->check = udp_v4_check(udplen, iph->saddr, + iph->daddr, csum); + break; +#if IS_ENABLED(CONFIG_IPV6) + case htons(ETH_P_IPV6): + ip6h = ipv6_hdr(skb); + uh->check = udp_v6_check(udplen, &ip6h->saddr, + &ip6h->daddr, csum); + break; +#endif + } + + uh->check = uh->check ?: CSUM_MANGLED_0; + skb->ip_summed = CHECKSUM_NONE; + } + +out_unlock: + rcu_read_unlock(); + return rc; +} + +static int +nsim_psp_set_config(struct psp_dev *psd, struct psp_dev_config *conf, + struct netlink_ext_ack *extack) +{ + return 0; +} + +static int +nsim_rx_spi_alloc(struct psp_dev *psd, u32 version, + struct psp_key_parsed *assoc, + struct netlink_ext_ack *extack) +{ + struct netdevsim *ns = psd->drv_priv; + int i; + + /* Check if incrementing the spi would change the phase bit */ + if ((ns->psp.spi & PSP_SPI_KEY_ID) == PSP_SPI_KEY_ID) { + NL_SET_ERR_MSG(extack, "SPI space exhausted"); + return -ENOSPC; + } + + assoc->spi = cpu_to_be32(++ns->psp.spi); + assoc->key[0] = psd->generation; + for (i = 1; i < PSP_MAX_KEY; i++) + assoc->key[i] = ns->psp.spi + i; + + return 0; +} + +static int nsim_assoc_add(struct psp_dev *psd, struct psp_assoc *pas, + struct netlink_ext_ack *extack) +{ + struct netdevsim *ns = psd->drv_priv; + void **ptr = psp_assoc_drv_data(pas); + + /* Copy drv_priv from psd to assoc */ + *ptr = psd->drv_priv; + ns->psp.assoc_cnt++; + + return 0; +} + +static int nsim_key_rotate(struct psp_dev *psd, struct netlink_ext_ack *extack) +{ + struct netdevsim *ns = psd->drv_priv; + + /* Flip key phase and reset SPI to 0 within that space + * (will be pre-incremented, as 0 is an invalid SPI). + */ + if (ns->psp.spi & PSP_SPI_KEY_PHASE) + ns->psp.spi = 0; + else + ns->psp.spi = PSP_SPI_KEY_PHASE; + + return 0; +} + +static void nsim_assoc_del(struct psp_dev *psd, struct psp_assoc *pas) +{ + struct netdevsim *ns = psd->drv_priv; + void **ptr = psp_assoc_drv_data(pas); + + *ptr = NULL; + ns->psp.assoc_cnt--; +} + +static void nsim_get_stats(struct psp_dev *psd, struct psp_dev_stats *stats) +{ + struct netdevsim *ns = psd->drv_priv; + + /* WARNING: do *not* blindly zero stats in real drivers! + * All required stats must be reported by the device! + */ + memset(stats, 0, sizeof(struct psp_dev_stats)); + + stats->rx_bytes = atomic64_read(&ns->psp.rx_bytes); + stats->rx_packets = atomic64_read(&ns->psp.rx_packets); + stats->tx_bytes = atomic64_read(&ns->psp.tx_bytes); + stats->tx_packets = atomic64_read(&ns->psp.tx_packets); +} + +static struct psp_dev_ops nsim_psp_ops = { + .set_config = nsim_psp_set_config, + .rx_spi_alloc = nsim_rx_spi_alloc, + .tx_key_add = nsim_assoc_add, + .tx_key_del = nsim_assoc_del, + .key_rotate = nsim_key_rotate, + .get_stats = nsim_get_stats, +}; + +static struct psp_dev_caps nsim_psp_caps = { + .versions = 1 << PSP_VERSION_HDR0_AES_GCM_128 | + 1 << PSP_VERSION_HDR0_AES_GMAC_128 | + 1 << PSP_VERSION_HDR0_AES_GCM_256 | + 1 << PSP_VERSION_HDR0_AES_GMAC_256, + .assoc_drv_spc = sizeof(void *), +}; + +static void __nsim_psp_uninit(struct netdevsim *ns, bool teardown) +{ + struct psp_dev *psd; + + psd = rcu_dereference_protected(ns->psp.dev, + teardown || + lockdep_is_held(&ns->psp.rereg_lock)); + if (psd) { + rcu_assign_pointer(ns->psp.dev, NULL); + synchronize_rcu(); + psp_dev_unregister(psd); + } + WARN_ON(ns->psp.assoc_cnt); +} + +void nsim_psp_uninit(struct netdevsim *ns) +{ + debugfs_remove(ns->psp.rereg); + mutex_destroy(&ns->psp.rereg_lock); + __nsim_psp_uninit(ns, true); +} + +static ssize_t +nsim_psp_rereg_write(struct file *file, const char __user *data, size_t count, + loff_t *ppos) +{ + struct netdevsim *ns = file->private_data; + struct psp_dev *psd; + ssize_t ret; + + mutex_lock(&ns->psp.rereg_lock); + __nsim_psp_uninit(ns, false); + + psd = psp_dev_create(ns->netdev, &nsim_psp_ops, &nsim_psp_caps, ns); + if (IS_ERR(psd)) { + ret = PTR_ERR(psd); + goto out; + } + + rcu_assign_pointer(ns->psp.dev, psd); + ret = count; +out: + mutex_unlock(&ns->psp.rereg_lock); + return ret; +} + +static const struct file_operations nsim_psp_rereg_fops = { + .open = simple_open, + .write = nsim_psp_rereg_write, + .llseek = generic_file_llseek, + .owner = THIS_MODULE, +}; + +int nsim_psp_init(struct netdevsim *ns) +{ + struct dentry *ddir = ns->nsim_dev_port->ddir; + struct psp_dev *psd; + + psd = psp_dev_create(ns->netdev, &nsim_psp_ops, &nsim_psp_caps, ns); + if (IS_ERR(psd)) + return PTR_ERR(psd); + + rcu_assign_pointer(ns->psp.dev, psd); + + mutex_init(&ns->psp.rereg_lock); + ns->psp.rereg = debugfs_create_file("psp_rereg", 0200, ddir, ns, + &nsim_psp_rereg_fops); + return 0; +} -- cgit v1.3.1