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 --- net/atm/proc.c | 333 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 333 insertions(+) create mode 100644 net/atm/proc.c (limited to 'net/atm/proc.c') diff --git a/net/atm/proc.c b/net/atm/proc.c new file mode 100644 index 000000000..8f20b49b9 --- /dev/null +++ b/net/atm/proc.c @@ -0,0 +1,333 @@ +// SPDX-License-Identifier: GPL-2.0 +/* net/atm/proc.c - ATM /proc interface + * + * Written 1995-2000 by Werner Almesberger, EPFL LRC/ICA + * + * seq_file api usage by romieu@fr.zoreil.com + * + * Evaluating the efficiency of the whole thing if left as an exercise to + * the reader. + */ + +#include /* for EXPORT_SYMBOL */ +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include /* for __init */ +#include +#include +#include +#include /* for HZ */ +#include +#include "resources.h" +#include "common.h" /* atm_proc_init prototype */ + +static ssize_t proc_dev_atm_read(struct file *file, char __user *buf, + size_t count, loff_t *pos); + +static const struct proc_ops atm_dev_proc_ops = { + .proc_read = proc_dev_atm_read, + .proc_lseek = noop_llseek, +}; + +static void add_stats(struct seq_file *seq, const char *aal, + const struct k_atm_aal_stats *stats) +{ + seq_printf(seq, "%s ( %d %d %d %d %d )", aal, + atomic_read(&stats->tx), atomic_read(&stats->tx_err), + atomic_read(&stats->rx), atomic_read(&stats->rx_err), + atomic_read(&stats->rx_drop)); +} + +static void atm_dev_info(struct seq_file *seq, const struct atm_dev *dev) +{ + int i; + + seq_printf(seq, "%3d %-8s", dev->number, dev->type); + for (i = 0; i < ESI_LEN; i++) + seq_printf(seq, "%02x", dev->esi[i]); + seq_puts(seq, " "); + add_stats(seq, "0", &dev->stats.aal0); + seq_puts(seq, " "); + add_stats(seq, "5", &dev->stats.aal5); + seq_printf(seq, "\t[%d]", refcount_read(&dev->refcnt)); + seq_putc(seq, '\n'); +} + +struct vcc_state { + int bucket; + struct sock *sk; +}; + +static inline int compare_family(struct sock *sk, int family) +{ + return !family || (sk->sk_family == family); +} + +static int __vcc_walk(struct sock **sock, int family, int *bucket, loff_t l) +{ + struct sock *sk = *sock; + + if (sk == SEQ_START_TOKEN) { + for (*bucket = 0; *bucket < VCC_HTABLE_SIZE; ++*bucket) { + struct hlist_head *head = &vcc_hash[*bucket]; + + sk = hlist_empty(head) ? NULL : __sk_head(head); + if (sk) + break; + } + l--; + } +try_again: + for (; sk; sk = sk_next(sk)) { + l -= compare_family(sk, family); + if (l < 0) + goto out; + } + if (!sk && ++*bucket < VCC_HTABLE_SIZE) { + sk = sk_head(&vcc_hash[*bucket]); + goto try_again; + } + sk = SEQ_START_TOKEN; +out: + *sock = sk; + return (l < 0); +} + +static inline void *vcc_walk(struct seq_file *seq, loff_t l) +{ + struct vcc_state *state = seq->private; + int family = (uintptr_t)(pde_data(file_inode(seq->file))); + + return __vcc_walk(&state->sk, family, &state->bucket, l) ? + state : NULL; +} + +static void *vcc_seq_start(struct seq_file *seq, loff_t *pos) + __acquires(vcc_sklist_lock) +{ + struct vcc_state *state = seq->private; + loff_t left = *pos; + + read_lock(&vcc_sklist_lock); + state->sk = SEQ_START_TOKEN; + return left ? vcc_walk(seq, left) : SEQ_START_TOKEN; +} + +static void vcc_seq_stop(struct seq_file *seq, void *v) + __releases(vcc_sklist_lock) +{ + read_unlock(&vcc_sklist_lock); +} + +static void *vcc_seq_next(struct seq_file *seq, void *v, loff_t *pos) +{ + v = vcc_walk(seq, 1); + (*pos)++; + return v; +} + +static void pvc_info(struct seq_file *seq, struct atm_vcc *vcc) +{ + static const char *const class_name[] = { + "off", "UBR", "CBR", "VBR", "ABR"}; + static const char *const aal_name[] = { + "---", "1", "2", "3/4", /* 0- 3 */ + "???", "5", "???", "???", /* 4- 7 */ + "???", "???", "???", "???", /* 8-11 */ + "???", "0", "???", "???"}; /* 12-15 */ + + seq_printf(seq, "%3d %3d %5d %-3s %7d %-5s %7d %-6s", + vcc->dev->number, vcc->vpi, vcc->vci, + vcc->qos.aal >= ARRAY_SIZE(aal_name) ? "err" : + aal_name[vcc->qos.aal], vcc->qos.rxtp.min_pcr, + class_name[vcc->qos.rxtp.traffic_class], + vcc->qos.txtp.min_pcr, + class_name[vcc->qos.txtp.traffic_class]); + seq_putc(seq, '\n'); +} + +static void vcc_info(struct seq_file *seq, struct atm_vcc *vcc) +{ + struct sock *sk = sk_atm(vcc); + + seq_printf(seq, "%pK ", vcc); + if (!vcc->dev) + seq_printf(seq, "Unassigned "); + else + seq_printf(seq, "%3d %3d %5d ", vcc->dev->number, vcc->vpi, + vcc->vci); + switch (sk->sk_family) { + case AF_ATMPVC: + seq_printf(seq, "PVC"); + break; + default: + seq_printf(seq, "%3d", sk->sk_family); + } + seq_printf(seq, " %04lx %5d %7d/%7d %7d/%7d [%d]\n", + vcc->flags, sk->sk_err, + sk_wmem_alloc_get(sk), sk->sk_sndbuf, + sk_rmem_alloc_get(sk), sk->sk_rcvbuf, + refcount_read(&sk->sk_refcnt)); +} + +static int atm_dev_seq_show(struct seq_file *seq, void *v) +{ + static char atm_dev_banner[] = + "Itf Type ESI/\"MAC\"addr " + "AAL(TX,err,RX,err,drop) ... [refcnt]\n"; + + if (v == &atm_devs) + seq_puts(seq, atm_dev_banner); + else { + struct atm_dev *dev = list_entry(v, struct atm_dev, dev_list); + + atm_dev_info(seq, dev); + } + return 0; +} + +static const struct seq_operations atm_dev_seq_ops = { + .start = atm_dev_seq_start, + .next = atm_dev_seq_next, + .stop = atm_dev_seq_stop, + .show = atm_dev_seq_show, +}; + +static int pvc_seq_show(struct seq_file *seq, void *v) +{ + static char atm_pvc_banner[] = + "Itf VPI VCI AAL RX(PCR,Class) TX(PCR,Class)\n"; + + if (v == SEQ_START_TOKEN) + seq_puts(seq, atm_pvc_banner); + else { + struct vcc_state *state = seq->private; + struct atm_vcc *vcc = atm_sk(state->sk); + + pvc_info(seq, vcc); + } + return 0; +} + +static const struct seq_operations pvc_seq_ops = { + .start = vcc_seq_start, + .next = vcc_seq_next, + .stop = vcc_seq_stop, + .show = pvc_seq_show, +}; + +static int vcc_seq_show(struct seq_file *seq, void *v) +{ + if (v == SEQ_START_TOKEN) { + seq_printf(seq, sizeof(void *) == 4 ? "%-8s%s" : "%-16s%s", + "Address ", "Itf VPI VCI Fam Flags Reply " + "Send buffer Recv buffer [refcnt]\n"); + } else { + struct vcc_state *state = seq->private; + struct atm_vcc *vcc = atm_sk(state->sk); + + vcc_info(seq, vcc); + } + return 0; +} + +static const struct seq_operations vcc_seq_ops = { + .start = vcc_seq_start, + .next = vcc_seq_next, + .stop = vcc_seq_stop, + .show = vcc_seq_show, +}; + +static ssize_t proc_dev_atm_read(struct file *file, char __user *buf, + size_t count, loff_t *pos) +{ + struct atm_dev *dev; + unsigned long page; + int length; + + if (count == 0) + return 0; + page = get_zeroed_page(GFP_KERNEL); + if (!page) + return -ENOMEM; + dev = pde_data(file_inode(file)); + if (!dev->ops->proc_read) + length = -EINVAL; + else { + length = dev->ops->proc_read(dev, pos, (char *)page); + if (length > count) + length = -EINVAL; + } + if (length >= 0) { + if (copy_to_user(buf, (char *)page, length)) + length = -EFAULT; + (*pos)++; + } + free_page(page); + return length; +} + +struct proc_dir_entry *atm_proc_root; +EXPORT_SYMBOL(atm_proc_root); + + +int atm_proc_dev_register(struct atm_dev *dev) +{ + int error; + + /* No proc info */ + if (!dev->ops->proc_read) + return 0; + + error = -ENOMEM; + dev->proc_name = kasprintf(GFP_KERNEL, "%s:%d", dev->type, dev->number); + if (!dev->proc_name) + goto err_out; + + dev->proc_entry = proc_create_data(dev->proc_name, 0, atm_proc_root, + &atm_dev_proc_ops, dev); + if (!dev->proc_entry) + goto err_free_name; + return 0; + +err_free_name: + kfree(dev->proc_name); +err_out: + return error; +} + +void atm_proc_dev_deregister(struct atm_dev *dev) +{ + if (!dev->ops->proc_read) + return; + + remove_proc_entry(dev->proc_name, atm_proc_root); + kfree(dev->proc_name); +} + +int __init atm_proc_init(void) +{ + atm_proc_root = proc_net_mkdir(&init_net, "atm", init_net.proc_net); + if (!atm_proc_root) + return -ENOMEM; + proc_create_seq("devices", 0444, atm_proc_root, &atm_dev_seq_ops); + proc_create_seq_private("pvc", 0444, atm_proc_root, &pvc_seq_ops, + sizeof(struct vcc_state), (void *)(uintptr_t)PF_ATMPVC); + proc_create_seq_private("vc", 0444, atm_proc_root, &vcc_seq_ops, + sizeof(struct vcc_state), NULL); + return 0; +} + +void atm_proc_exit(void) +{ + remove_proc_subtree("atm", init_net.proc_net); +} -- cgit v1.3.1