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![Chuang Wang](/assets/img/avatar_default.png)
In the scenario where livepatch and kretfunc coexist, the pageattr of
im->image is rox after arch_prepare_bpf_trampoline in
bpf_trampoline_update, and then modify_fentry or register_fentry returns
-EAGAIN from bpf_tramp_ftrace_ops_func, the BPF_TRAMP_F_ORIG_STACK flag
will be configured, and arch_prepare_bpf_trampoline will be re-executed.
At this time, because the pageattr of im->image is rox,
arch_prepare_bpf_trampoline will read and write im->image, which causes
a fault. as follows:
insmod livepatch-sample.ko # samples/livepatch/livepatch-sample.c
bpftrace -e 'kretfunc:cmdline_proc_show {}'
BUG: unable to handle page fault for address: ffffffffa0206000
PGD 322d067 P4D 322d067 PUD 322e063 PMD 1297e067 PTE d428061
Oops: 0003 [#1] PREEMPT SMP PTI
CPU: 2 PID: 270 Comm: bpftrace Tainted: G E K 6.1.0 #5
RIP: 0010:arch_prepare_bpf_trampoline+0xed/0x8c0
RSP: 0018:ffffc90001083ad8 EFLAGS: 00010202
RAX: ffffffffa0206000 RBX: 0000000000000020 RCX: 0000000000000000
RDX: ffffffffa0206001 RSI: ffffffffa0206000 RDI: 0000000000000030
RBP: ffffc90001083b70 R08: 0000000000000066 R09: ffff88800f51b400
R10: 000000002e72c6e5 R11: 00000000d0a15080 R12: ffff8880110a68c8
R13: 0000000000000000 R14: ffff88800f51b400 R15: ffffffff814fec10
FS: 00007f87bc0dc780(0000) GS:ffff88803e600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffa0206000 CR3: 0000000010b70000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
bpf_trampoline_update+0x25a/0x6b0
__bpf_trampoline_link_prog+0x101/0x240
bpf_trampoline_link_prog+0x2d/0x50
bpf_tracing_prog_attach+0x24c/0x530
bpf_raw_tp_link_attach+0x73/0x1d0
__sys_bpf+0x100e/0x2570
__x64_sys_bpf+0x1c/0x30
do_syscall_64+0x5b/0x80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
With this patch, when modify_fentry or register_fentry returns -EAGAIN
from bpf_tramp_ftrace_ops_func, the pageattr of im->image will be reset
to nx+rw.
Cc: stable@vger.kernel.org
Fixes: 00963a2e75
("bpf: Support bpf_trampoline on functions with IPMODIFY (e.g. livepatch)")
Signed-off-by: Chuang Wang <nashuiliang@gmail.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20221224133146.780578-1-nashuiliang@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
1074 lines
27 KiB
C
1074 lines
27 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/* Copyright (c) 2019 Facebook */
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#include <linux/hash.h>
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#include <linux/bpf.h>
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#include <linux/filter.h>
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#include <linux/ftrace.h>
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#include <linux/rbtree_latch.h>
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#include <linux/perf_event.h>
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#include <linux/btf.h>
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#include <linux/rcupdate_trace.h>
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#include <linux/rcupdate_wait.h>
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#include <linux/module.h>
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#include <linux/static_call.h>
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#include <linux/bpf_verifier.h>
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#include <linux/bpf_lsm.h>
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#include <linux/delay.h>
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/* dummy _ops. The verifier will operate on target program's ops. */
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const struct bpf_verifier_ops bpf_extension_verifier_ops = {
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};
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const struct bpf_prog_ops bpf_extension_prog_ops = {
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};
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/* btf_vmlinux has ~22k attachable functions. 1k htab is enough. */
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#define TRAMPOLINE_HASH_BITS 10
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#define TRAMPOLINE_TABLE_SIZE (1 << TRAMPOLINE_HASH_BITS)
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static struct hlist_head trampoline_table[TRAMPOLINE_TABLE_SIZE];
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/* serializes access to trampoline_table */
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static DEFINE_MUTEX(trampoline_mutex);
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
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static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex);
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static int bpf_tramp_ftrace_ops_func(struct ftrace_ops *ops, enum ftrace_ops_cmd cmd)
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{
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struct bpf_trampoline *tr = ops->private;
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int ret = 0;
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if (cmd == FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_SELF) {
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/* This is called inside register_ftrace_direct_multi(), so
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* tr->mutex is already locked.
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*/
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lockdep_assert_held_once(&tr->mutex);
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/* Instead of updating the trampoline here, we propagate
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* -EAGAIN to register_ftrace_direct_multi(). Then we can
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* retry register_ftrace_direct_multi() after updating the
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* trampoline.
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*/
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if ((tr->flags & BPF_TRAMP_F_CALL_ORIG) &&
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!(tr->flags & BPF_TRAMP_F_ORIG_STACK)) {
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if (WARN_ON_ONCE(tr->flags & BPF_TRAMP_F_SHARE_IPMODIFY))
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return -EBUSY;
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tr->flags |= BPF_TRAMP_F_SHARE_IPMODIFY;
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return -EAGAIN;
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}
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return 0;
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}
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/* The normal locking order is
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* tr->mutex => direct_mutex (ftrace.c) => ftrace_lock (ftrace.c)
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*
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* The following two commands are called from
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*
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* prepare_direct_functions_for_ipmodify
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* cleanup_direct_functions_after_ipmodify
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*
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* In both cases, direct_mutex is already locked. Use
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* mutex_trylock(&tr->mutex) to avoid deadlock in race condition
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* (something else is making changes to this same trampoline).
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*/
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if (!mutex_trylock(&tr->mutex)) {
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/* sleep 1 ms to make sure whatever holding tr->mutex makes
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* some progress.
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*/
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msleep(1);
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return -EAGAIN;
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}
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switch (cmd) {
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case FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_PEER:
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tr->flags |= BPF_TRAMP_F_SHARE_IPMODIFY;
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if ((tr->flags & BPF_TRAMP_F_CALL_ORIG) &&
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!(tr->flags & BPF_TRAMP_F_ORIG_STACK))
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ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */);
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break;
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case FTRACE_OPS_CMD_DISABLE_SHARE_IPMODIFY_PEER:
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tr->flags &= ~BPF_TRAMP_F_SHARE_IPMODIFY;
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if (tr->flags & BPF_TRAMP_F_ORIG_STACK)
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ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */);
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break;
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default:
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ret = -EINVAL;
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break;
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}
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mutex_unlock(&tr->mutex);
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return ret;
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}
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#endif
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bool bpf_prog_has_trampoline(const struct bpf_prog *prog)
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{
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enum bpf_attach_type eatype = prog->expected_attach_type;
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enum bpf_prog_type ptype = prog->type;
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return (ptype == BPF_PROG_TYPE_TRACING &&
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(eatype == BPF_TRACE_FENTRY || eatype == BPF_TRACE_FEXIT ||
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eatype == BPF_MODIFY_RETURN)) ||
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(ptype == BPF_PROG_TYPE_LSM && eatype == BPF_LSM_MAC);
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}
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void bpf_image_ksym_add(void *data, struct bpf_ksym *ksym)
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{
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ksym->start = (unsigned long) data;
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ksym->end = ksym->start + PAGE_SIZE;
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bpf_ksym_add(ksym);
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perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
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PAGE_SIZE, false, ksym->name);
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}
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void bpf_image_ksym_del(struct bpf_ksym *ksym)
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{
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bpf_ksym_del(ksym);
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perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
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PAGE_SIZE, true, ksym->name);
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}
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static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
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{
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struct bpf_trampoline *tr;
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struct hlist_head *head;
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int i;
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mutex_lock(&trampoline_mutex);
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head = &trampoline_table[hash_64(key, TRAMPOLINE_HASH_BITS)];
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hlist_for_each_entry(tr, head, hlist) {
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if (tr->key == key) {
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refcount_inc(&tr->refcnt);
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goto out;
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}
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}
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tr = kzalloc(sizeof(*tr), GFP_KERNEL);
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if (!tr)
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goto out;
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
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tr->fops = kzalloc(sizeof(struct ftrace_ops), GFP_KERNEL);
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if (!tr->fops) {
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kfree(tr);
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tr = NULL;
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goto out;
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}
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tr->fops->private = tr;
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tr->fops->ops_func = bpf_tramp_ftrace_ops_func;
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#endif
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tr->key = key;
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INIT_HLIST_NODE(&tr->hlist);
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hlist_add_head(&tr->hlist, head);
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refcount_set(&tr->refcnt, 1);
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mutex_init(&tr->mutex);
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for (i = 0; i < BPF_TRAMP_MAX; i++)
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INIT_HLIST_HEAD(&tr->progs_hlist[i]);
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out:
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mutex_unlock(&trampoline_mutex);
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return tr;
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}
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static int bpf_trampoline_module_get(struct bpf_trampoline *tr)
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{
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struct module *mod;
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int err = 0;
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preempt_disable();
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mod = __module_text_address((unsigned long) tr->func.addr);
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if (mod && !try_module_get(mod))
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err = -ENOENT;
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preempt_enable();
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tr->mod = mod;
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return err;
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}
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static void bpf_trampoline_module_put(struct bpf_trampoline *tr)
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{
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module_put(tr->mod);
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tr->mod = NULL;
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}
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static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
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{
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void *ip = tr->func.addr;
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int ret;
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if (tr->func.ftrace_managed)
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ret = unregister_ftrace_direct_multi(tr->fops, (long)old_addr);
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else
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ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL);
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if (!ret)
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bpf_trampoline_module_put(tr);
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return ret;
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}
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static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_addr,
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bool lock_direct_mutex)
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{
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void *ip = tr->func.addr;
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int ret;
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if (tr->func.ftrace_managed) {
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if (lock_direct_mutex)
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ret = modify_ftrace_direct_multi(tr->fops, (long)new_addr);
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else
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ret = modify_ftrace_direct_multi_nolock(tr->fops, (long)new_addr);
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} else {
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ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, new_addr);
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}
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return ret;
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}
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/* first time registering */
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static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
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{
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void *ip = tr->func.addr;
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unsigned long faddr;
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int ret;
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faddr = ftrace_location((unsigned long)ip);
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if (faddr) {
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if (!tr->fops)
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return -ENOTSUPP;
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tr->func.ftrace_managed = true;
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}
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if (bpf_trampoline_module_get(tr))
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return -ENOENT;
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if (tr->func.ftrace_managed) {
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ftrace_set_filter_ip(tr->fops, (unsigned long)ip, 0, 1);
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ret = register_ftrace_direct_multi(tr->fops, (long)new_addr);
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} else {
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ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
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}
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if (ret)
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bpf_trampoline_module_put(tr);
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return ret;
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}
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static struct bpf_tramp_links *
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bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total, bool *ip_arg)
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{
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struct bpf_tramp_link *link;
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struct bpf_tramp_links *tlinks;
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struct bpf_tramp_link **links;
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int kind;
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*total = 0;
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tlinks = kcalloc(BPF_TRAMP_MAX, sizeof(*tlinks), GFP_KERNEL);
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if (!tlinks)
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return ERR_PTR(-ENOMEM);
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for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {
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tlinks[kind].nr_links = tr->progs_cnt[kind];
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*total += tr->progs_cnt[kind];
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links = tlinks[kind].links;
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hlist_for_each_entry(link, &tr->progs_hlist[kind], tramp_hlist) {
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*ip_arg |= link->link.prog->call_get_func_ip;
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*links++ = link;
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}
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}
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return tlinks;
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}
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static void __bpf_tramp_image_put_deferred(struct work_struct *work)
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{
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struct bpf_tramp_image *im;
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im = container_of(work, struct bpf_tramp_image, work);
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bpf_image_ksym_del(&im->ksym);
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bpf_jit_free_exec(im->image);
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bpf_jit_uncharge_modmem(PAGE_SIZE);
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percpu_ref_exit(&im->pcref);
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kfree_rcu(im, rcu);
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}
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/* callback, fexit step 3 or fentry step 2 */
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static void __bpf_tramp_image_put_rcu(struct rcu_head *rcu)
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{
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struct bpf_tramp_image *im;
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im = container_of(rcu, struct bpf_tramp_image, rcu);
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INIT_WORK(&im->work, __bpf_tramp_image_put_deferred);
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schedule_work(&im->work);
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}
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/* callback, fexit step 2. Called after percpu_ref_kill confirms. */
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static void __bpf_tramp_image_release(struct percpu_ref *pcref)
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{
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struct bpf_tramp_image *im;
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im = container_of(pcref, struct bpf_tramp_image, pcref);
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call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu);
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}
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/* callback, fexit or fentry step 1 */
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static void __bpf_tramp_image_put_rcu_tasks(struct rcu_head *rcu)
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{
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struct bpf_tramp_image *im;
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im = container_of(rcu, struct bpf_tramp_image, rcu);
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if (im->ip_after_call)
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/* the case of fmod_ret/fexit trampoline and CONFIG_PREEMPTION=y */
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percpu_ref_kill(&im->pcref);
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else
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/* the case of fentry trampoline */
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call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu);
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}
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static void bpf_tramp_image_put(struct bpf_tramp_image *im)
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{
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/* The trampoline image that calls original function is using:
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* rcu_read_lock_trace to protect sleepable bpf progs
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* rcu_read_lock to protect normal bpf progs
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* percpu_ref to protect trampoline itself
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* rcu tasks to protect trampoline asm not covered by percpu_ref
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* (which are few asm insns before __bpf_tramp_enter and
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* after __bpf_tramp_exit)
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*
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* The trampoline is unreachable before bpf_tramp_image_put().
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*
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* First, patch the trampoline to avoid calling into fexit progs.
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* The progs will be freed even if the original function is still
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* executing or sleeping.
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* In case of CONFIG_PREEMPT=y use call_rcu_tasks() to wait on
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* first few asm instructions to execute and call into
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* __bpf_tramp_enter->percpu_ref_get.
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* Then use percpu_ref_kill to wait for the trampoline and the original
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* function to finish.
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* Then use call_rcu_tasks() to make sure few asm insns in
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* the trampoline epilogue are done as well.
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*
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* In !PREEMPT case the task that got interrupted in the first asm
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* insns won't go through an RCU quiescent state which the
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* percpu_ref_kill will be waiting for. Hence the first
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* call_rcu_tasks() is not necessary.
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*/
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if (im->ip_after_call) {
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int err = bpf_arch_text_poke(im->ip_after_call, BPF_MOD_JUMP,
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NULL, im->ip_epilogue);
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WARN_ON(err);
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if (IS_ENABLED(CONFIG_PREEMPTION))
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call_rcu_tasks(&im->rcu, __bpf_tramp_image_put_rcu_tasks);
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else
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percpu_ref_kill(&im->pcref);
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return;
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}
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|
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/* The trampoline without fexit and fmod_ret progs doesn't call original
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* function and doesn't use percpu_ref.
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* Use call_rcu_tasks_trace() to wait for sleepable progs to finish.
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* Then use call_rcu_tasks() to wait for the rest of trampoline asm
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* and normal progs.
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*/
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call_rcu_tasks_trace(&im->rcu, __bpf_tramp_image_put_rcu_tasks);
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}
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static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, u32 idx)
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{
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struct bpf_tramp_image *im;
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struct bpf_ksym *ksym;
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void *image;
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int err = -ENOMEM;
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im = kzalloc(sizeof(*im), GFP_KERNEL);
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if (!im)
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goto out;
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err = bpf_jit_charge_modmem(PAGE_SIZE);
|
|
if (err)
|
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goto out_free_im;
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err = -ENOMEM;
|
|
im->image = image = bpf_jit_alloc_exec(PAGE_SIZE);
|
|
if (!image)
|
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goto out_uncharge;
|
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set_vm_flush_reset_perms(image);
|
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|
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err = percpu_ref_init(&im->pcref, __bpf_tramp_image_release, 0, GFP_KERNEL);
|
|
if (err)
|
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goto out_free_image;
|
|
|
|
ksym = &im->ksym;
|
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INIT_LIST_HEAD_RCU(&ksym->lnode);
|
|
snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu_%u", key, idx);
|
|
bpf_image_ksym_add(image, ksym);
|
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return im;
|
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|
|
out_free_image:
|
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bpf_jit_free_exec(im->image);
|
|
out_uncharge:
|
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bpf_jit_uncharge_modmem(PAGE_SIZE);
|
|
out_free_im:
|
|
kfree(im);
|
|
out:
|
|
return ERR_PTR(err);
|
|
}
|
|
|
|
static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex)
|
|
{
|
|
struct bpf_tramp_image *im;
|
|
struct bpf_tramp_links *tlinks;
|
|
u32 orig_flags = tr->flags;
|
|
bool ip_arg = false;
|
|
int err, total;
|
|
|
|
tlinks = bpf_trampoline_get_progs(tr, &total, &ip_arg);
|
|
if (IS_ERR(tlinks))
|
|
return PTR_ERR(tlinks);
|
|
|
|
if (total == 0) {
|
|
err = unregister_fentry(tr, tr->cur_image->image);
|
|
bpf_tramp_image_put(tr->cur_image);
|
|
tr->cur_image = NULL;
|
|
tr->selector = 0;
|
|
goto out;
|
|
}
|
|
|
|
im = bpf_tramp_image_alloc(tr->key, tr->selector);
|
|
if (IS_ERR(im)) {
|
|
err = PTR_ERR(im);
|
|
goto out;
|
|
}
|
|
|
|
/* clear all bits except SHARE_IPMODIFY */
|
|
tr->flags &= BPF_TRAMP_F_SHARE_IPMODIFY;
|
|
|
|
if (tlinks[BPF_TRAMP_FEXIT].nr_links ||
|
|
tlinks[BPF_TRAMP_MODIFY_RETURN].nr_links) {
|
|
/* NOTE: BPF_TRAMP_F_RESTORE_REGS and BPF_TRAMP_F_SKIP_FRAME
|
|
* should not be set together.
|
|
*/
|
|
tr->flags |= BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
|
|
} else {
|
|
tr->flags |= BPF_TRAMP_F_RESTORE_REGS;
|
|
}
|
|
|
|
if (ip_arg)
|
|
tr->flags |= BPF_TRAMP_F_IP_ARG;
|
|
|
|
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
|
|
again:
|
|
if ((tr->flags & BPF_TRAMP_F_SHARE_IPMODIFY) &&
|
|
(tr->flags & BPF_TRAMP_F_CALL_ORIG))
|
|
tr->flags |= BPF_TRAMP_F_ORIG_STACK;
|
|
#endif
|
|
|
|
err = arch_prepare_bpf_trampoline(im, im->image, im->image + PAGE_SIZE,
|
|
&tr->func.model, tr->flags, tlinks,
|
|
tr->func.addr);
|
|
if (err < 0)
|
|
goto out;
|
|
|
|
set_memory_rox((long)im->image, 1);
|
|
|
|
WARN_ON(tr->cur_image && tr->selector == 0);
|
|
WARN_ON(!tr->cur_image && tr->selector);
|
|
if (tr->cur_image)
|
|
/* progs already running at this address */
|
|
err = modify_fentry(tr, tr->cur_image->image, im->image, lock_direct_mutex);
|
|
else
|
|
/* first time registering */
|
|
err = register_fentry(tr, im->image);
|
|
|
|
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
|
|
if (err == -EAGAIN) {
|
|
/* -EAGAIN from bpf_tramp_ftrace_ops_func. Now
|
|
* BPF_TRAMP_F_SHARE_IPMODIFY is set, we can generate the
|
|
* trampoline again, and retry register.
|
|
*/
|
|
/* reset fops->func and fops->trampoline for re-register */
|
|
tr->fops->func = NULL;
|
|
tr->fops->trampoline = 0;
|
|
|
|
/* reset im->image memory attr for arch_prepare_bpf_trampoline */
|
|
set_memory_nx((long)im->image, 1);
|
|
set_memory_rw((long)im->image, 1);
|
|
goto again;
|
|
}
|
|
#endif
|
|
if (err)
|
|
goto out;
|
|
|
|
if (tr->cur_image)
|
|
bpf_tramp_image_put(tr->cur_image);
|
|
tr->cur_image = im;
|
|
tr->selector++;
|
|
out:
|
|
/* If any error happens, restore previous flags */
|
|
if (err)
|
|
tr->flags = orig_flags;
|
|
kfree(tlinks);
|
|
return err;
|
|
}
|
|
|
|
static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(struct bpf_prog *prog)
|
|
{
|
|
switch (prog->expected_attach_type) {
|
|
case BPF_TRACE_FENTRY:
|
|
return BPF_TRAMP_FENTRY;
|
|
case BPF_MODIFY_RETURN:
|
|
return BPF_TRAMP_MODIFY_RETURN;
|
|
case BPF_TRACE_FEXIT:
|
|
return BPF_TRAMP_FEXIT;
|
|
case BPF_LSM_MAC:
|
|
if (!prog->aux->attach_func_proto->type)
|
|
/* The function returns void, we cannot modify its
|
|
* return value.
|
|
*/
|
|
return BPF_TRAMP_FEXIT;
|
|
else
|
|
return BPF_TRAMP_MODIFY_RETURN;
|
|
default:
|
|
return BPF_TRAMP_REPLACE;
|
|
}
|
|
}
|
|
|
|
static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
|
|
{
|
|
enum bpf_tramp_prog_type kind;
|
|
struct bpf_tramp_link *link_exiting;
|
|
int err = 0;
|
|
int cnt = 0, i;
|
|
|
|
kind = bpf_attach_type_to_tramp(link->link.prog);
|
|
if (tr->extension_prog)
|
|
/* cannot attach fentry/fexit if extension prog is attached.
|
|
* cannot overwrite extension prog either.
|
|
*/
|
|
return -EBUSY;
|
|
|
|
for (i = 0; i < BPF_TRAMP_MAX; i++)
|
|
cnt += tr->progs_cnt[i];
|
|
|
|
if (kind == BPF_TRAMP_REPLACE) {
|
|
/* Cannot attach extension if fentry/fexit are in use. */
|
|
if (cnt)
|
|
return -EBUSY;
|
|
tr->extension_prog = link->link.prog;
|
|
return bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP, NULL,
|
|
link->link.prog->bpf_func);
|
|
}
|
|
if (cnt >= BPF_MAX_TRAMP_LINKS)
|
|
return -E2BIG;
|
|
if (!hlist_unhashed(&link->tramp_hlist))
|
|
/* prog already linked */
|
|
return -EBUSY;
|
|
hlist_for_each_entry(link_exiting, &tr->progs_hlist[kind], tramp_hlist) {
|
|
if (link_exiting->link.prog != link->link.prog)
|
|
continue;
|
|
/* prog already linked */
|
|
return -EBUSY;
|
|
}
|
|
|
|
hlist_add_head(&link->tramp_hlist, &tr->progs_hlist[kind]);
|
|
tr->progs_cnt[kind]++;
|
|
err = bpf_trampoline_update(tr, true /* lock_direct_mutex */);
|
|
if (err) {
|
|
hlist_del_init(&link->tramp_hlist);
|
|
tr->progs_cnt[kind]--;
|
|
}
|
|
return err;
|
|
}
|
|
|
|
int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
|
|
{
|
|
int err;
|
|
|
|
mutex_lock(&tr->mutex);
|
|
err = __bpf_trampoline_link_prog(link, tr);
|
|
mutex_unlock(&tr->mutex);
|
|
return err;
|
|
}
|
|
|
|
static int __bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
|
|
{
|
|
enum bpf_tramp_prog_type kind;
|
|
int err;
|
|
|
|
kind = bpf_attach_type_to_tramp(link->link.prog);
|
|
if (kind == BPF_TRAMP_REPLACE) {
|
|
WARN_ON_ONCE(!tr->extension_prog);
|
|
err = bpf_arch_text_poke(tr->func.addr, BPF_MOD_JUMP,
|
|
tr->extension_prog->bpf_func, NULL);
|
|
tr->extension_prog = NULL;
|
|
return err;
|
|
}
|
|
hlist_del_init(&link->tramp_hlist);
|
|
tr->progs_cnt[kind]--;
|
|
return bpf_trampoline_update(tr, true /* lock_direct_mutex */);
|
|
}
|
|
|
|
/* bpf_trampoline_unlink_prog() should never fail. */
|
|
int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr)
|
|
{
|
|
int err;
|
|
|
|
mutex_lock(&tr->mutex);
|
|
err = __bpf_trampoline_unlink_prog(link, tr);
|
|
mutex_unlock(&tr->mutex);
|
|
return err;
|
|
}
|
|
|
|
#if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_BPF_LSM)
|
|
static void bpf_shim_tramp_link_release(struct bpf_link *link)
|
|
{
|
|
struct bpf_shim_tramp_link *shim_link =
|
|
container_of(link, struct bpf_shim_tramp_link, link.link);
|
|
|
|
/* paired with 'shim_link->trampoline = tr' in bpf_trampoline_link_cgroup_shim */
|
|
if (!shim_link->trampoline)
|
|
return;
|
|
|
|
WARN_ON_ONCE(bpf_trampoline_unlink_prog(&shim_link->link, shim_link->trampoline));
|
|
bpf_trampoline_put(shim_link->trampoline);
|
|
}
|
|
|
|
static void bpf_shim_tramp_link_dealloc(struct bpf_link *link)
|
|
{
|
|
struct bpf_shim_tramp_link *shim_link =
|
|
container_of(link, struct bpf_shim_tramp_link, link.link);
|
|
|
|
kfree(shim_link);
|
|
}
|
|
|
|
static const struct bpf_link_ops bpf_shim_tramp_link_lops = {
|
|
.release = bpf_shim_tramp_link_release,
|
|
.dealloc = bpf_shim_tramp_link_dealloc,
|
|
};
|
|
|
|
static struct bpf_shim_tramp_link *cgroup_shim_alloc(const struct bpf_prog *prog,
|
|
bpf_func_t bpf_func,
|
|
int cgroup_atype)
|
|
{
|
|
struct bpf_shim_tramp_link *shim_link = NULL;
|
|
struct bpf_prog *p;
|
|
|
|
shim_link = kzalloc(sizeof(*shim_link), GFP_USER);
|
|
if (!shim_link)
|
|
return NULL;
|
|
|
|
p = bpf_prog_alloc(1, 0);
|
|
if (!p) {
|
|
kfree(shim_link);
|
|
return NULL;
|
|
}
|
|
|
|
p->jited = false;
|
|
p->bpf_func = bpf_func;
|
|
|
|
p->aux->cgroup_atype = cgroup_atype;
|
|
p->aux->attach_func_proto = prog->aux->attach_func_proto;
|
|
p->aux->attach_btf_id = prog->aux->attach_btf_id;
|
|
p->aux->attach_btf = prog->aux->attach_btf;
|
|
btf_get(p->aux->attach_btf);
|
|
p->type = BPF_PROG_TYPE_LSM;
|
|
p->expected_attach_type = BPF_LSM_MAC;
|
|
bpf_prog_inc(p);
|
|
bpf_link_init(&shim_link->link.link, BPF_LINK_TYPE_UNSPEC,
|
|
&bpf_shim_tramp_link_lops, p);
|
|
bpf_cgroup_atype_get(p->aux->attach_btf_id, cgroup_atype);
|
|
|
|
return shim_link;
|
|
}
|
|
|
|
static struct bpf_shim_tramp_link *cgroup_shim_find(struct bpf_trampoline *tr,
|
|
bpf_func_t bpf_func)
|
|
{
|
|
struct bpf_tramp_link *link;
|
|
int kind;
|
|
|
|
for (kind = 0; kind < BPF_TRAMP_MAX; kind++) {
|
|
hlist_for_each_entry(link, &tr->progs_hlist[kind], tramp_hlist) {
|
|
struct bpf_prog *p = link->link.prog;
|
|
|
|
if (p->bpf_func == bpf_func)
|
|
return container_of(link, struct bpf_shim_tramp_link, link);
|
|
}
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
|
|
int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog,
|
|
int cgroup_atype)
|
|
{
|
|
struct bpf_shim_tramp_link *shim_link = NULL;
|
|
struct bpf_attach_target_info tgt_info = {};
|
|
struct bpf_trampoline *tr;
|
|
bpf_func_t bpf_func;
|
|
u64 key;
|
|
int err;
|
|
|
|
err = bpf_check_attach_target(NULL, prog, NULL,
|
|
prog->aux->attach_btf_id,
|
|
&tgt_info);
|
|
if (err)
|
|
return err;
|
|
|
|
key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf,
|
|
prog->aux->attach_btf_id);
|
|
|
|
bpf_lsm_find_cgroup_shim(prog, &bpf_func);
|
|
tr = bpf_trampoline_get(key, &tgt_info);
|
|
if (!tr)
|
|
return -ENOMEM;
|
|
|
|
mutex_lock(&tr->mutex);
|
|
|
|
shim_link = cgroup_shim_find(tr, bpf_func);
|
|
if (shim_link) {
|
|
/* Reusing existing shim attached by the other program. */
|
|
bpf_link_inc(&shim_link->link.link);
|
|
|
|
mutex_unlock(&tr->mutex);
|
|
bpf_trampoline_put(tr); /* bpf_trampoline_get above */
|
|
return 0;
|
|
}
|
|
|
|
/* Allocate and install new shim. */
|
|
|
|
shim_link = cgroup_shim_alloc(prog, bpf_func, cgroup_atype);
|
|
if (!shim_link) {
|
|
err = -ENOMEM;
|
|
goto err;
|
|
}
|
|
|
|
err = __bpf_trampoline_link_prog(&shim_link->link, tr);
|
|
if (err)
|
|
goto err;
|
|
|
|
shim_link->trampoline = tr;
|
|
/* note, we're still holding tr refcnt from above */
|
|
|
|
mutex_unlock(&tr->mutex);
|
|
|
|
return 0;
|
|
err:
|
|
mutex_unlock(&tr->mutex);
|
|
|
|
if (shim_link)
|
|
bpf_link_put(&shim_link->link.link);
|
|
|
|
/* have to release tr while _not_ holding its mutex */
|
|
bpf_trampoline_put(tr); /* bpf_trampoline_get above */
|
|
|
|
return err;
|
|
}
|
|
|
|
void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog)
|
|
{
|
|
struct bpf_shim_tramp_link *shim_link = NULL;
|
|
struct bpf_trampoline *tr;
|
|
bpf_func_t bpf_func;
|
|
u64 key;
|
|
|
|
key = bpf_trampoline_compute_key(NULL, prog->aux->attach_btf,
|
|
prog->aux->attach_btf_id);
|
|
|
|
bpf_lsm_find_cgroup_shim(prog, &bpf_func);
|
|
tr = bpf_trampoline_lookup(key);
|
|
if (WARN_ON_ONCE(!tr))
|
|
return;
|
|
|
|
mutex_lock(&tr->mutex);
|
|
shim_link = cgroup_shim_find(tr, bpf_func);
|
|
mutex_unlock(&tr->mutex);
|
|
|
|
if (shim_link)
|
|
bpf_link_put(&shim_link->link.link);
|
|
|
|
bpf_trampoline_put(tr); /* bpf_trampoline_lookup above */
|
|
}
|
|
#endif
|
|
|
|
struct bpf_trampoline *bpf_trampoline_get(u64 key,
|
|
struct bpf_attach_target_info *tgt_info)
|
|
{
|
|
struct bpf_trampoline *tr;
|
|
|
|
tr = bpf_trampoline_lookup(key);
|
|
if (!tr)
|
|
return NULL;
|
|
|
|
mutex_lock(&tr->mutex);
|
|
if (tr->func.addr)
|
|
goto out;
|
|
|
|
memcpy(&tr->func.model, &tgt_info->fmodel, sizeof(tgt_info->fmodel));
|
|
tr->func.addr = (void *)tgt_info->tgt_addr;
|
|
out:
|
|
mutex_unlock(&tr->mutex);
|
|
return tr;
|
|
}
|
|
|
|
void bpf_trampoline_put(struct bpf_trampoline *tr)
|
|
{
|
|
int i;
|
|
|
|
if (!tr)
|
|
return;
|
|
mutex_lock(&trampoline_mutex);
|
|
if (!refcount_dec_and_test(&tr->refcnt))
|
|
goto out;
|
|
WARN_ON_ONCE(mutex_is_locked(&tr->mutex));
|
|
|
|
for (i = 0; i < BPF_TRAMP_MAX; i++)
|
|
if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[i])))
|
|
goto out;
|
|
|
|
/* This code will be executed even when the last bpf_tramp_image
|
|
* is alive. All progs are detached from the trampoline and the
|
|
* trampoline image is patched with jmp into epilogue to skip
|
|
* fexit progs. The fentry-only trampoline will be freed via
|
|
* multiple rcu callbacks.
|
|
*/
|
|
hlist_del(&tr->hlist);
|
|
if (tr->fops) {
|
|
ftrace_free_filter(tr->fops);
|
|
kfree(tr->fops);
|
|
}
|
|
kfree(tr);
|
|
out:
|
|
mutex_unlock(&trampoline_mutex);
|
|
}
|
|
|
|
#define NO_START_TIME 1
|
|
static __always_inline u64 notrace bpf_prog_start_time(void)
|
|
{
|
|
u64 start = NO_START_TIME;
|
|
|
|
if (static_branch_unlikely(&bpf_stats_enabled_key)) {
|
|
start = sched_clock();
|
|
if (unlikely(!start))
|
|
start = NO_START_TIME;
|
|
}
|
|
return start;
|
|
}
|
|
|
|
/* The logic is similar to bpf_prog_run(), but with an explicit
|
|
* rcu_read_lock() and migrate_disable() which are required
|
|
* for the trampoline. The macro is split into
|
|
* call __bpf_prog_enter
|
|
* call prog->bpf_func
|
|
* call __bpf_prog_exit
|
|
*
|
|
* __bpf_prog_enter returns:
|
|
* 0 - skip execution of the bpf prog
|
|
* 1 - execute bpf prog
|
|
* [2..MAX_U64] - execute bpf prog and record execution time.
|
|
* This is start time.
|
|
*/
|
|
static u64 notrace __bpf_prog_enter_recur(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx)
|
|
__acquires(RCU)
|
|
{
|
|
rcu_read_lock();
|
|
migrate_disable();
|
|
|
|
run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
|
|
|
|
if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
|
|
bpf_prog_inc_misses_counter(prog);
|
|
return 0;
|
|
}
|
|
return bpf_prog_start_time();
|
|
}
|
|
|
|
static void notrace update_prog_stats(struct bpf_prog *prog,
|
|
u64 start)
|
|
{
|
|
struct bpf_prog_stats *stats;
|
|
|
|
if (static_branch_unlikely(&bpf_stats_enabled_key) &&
|
|
/* static_key could be enabled in __bpf_prog_enter*
|
|
* and disabled in __bpf_prog_exit*.
|
|
* And vice versa.
|
|
* Hence check that 'start' is valid.
|
|
*/
|
|
start > NO_START_TIME) {
|
|
unsigned long flags;
|
|
|
|
stats = this_cpu_ptr(prog->stats);
|
|
flags = u64_stats_update_begin_irqsave(&stats->syncp);
|
|
u64_stats_inc(&stats->cnt);
|
|
u64_stats_add(&stats->nsecs, sched_clock() - start);
|
|
u64_stats_update_end_irqrestore(&stats->syncp, flags);
|
|
}
|
|
}
|
|
|
|
static void notrace __bpf_prog_exit_recur(struct bpf_prog *prog, u64 start,
|
|
struct bpf_tramp_run_ctx *run_ctx)
|
|
__releases(RCU)
|
|
{
|
|
bpf_reset_run_ctx(run_ctx->saved_run_ctx);
|
|
|
|
update_prog_stats(prog, start);
|
|
this_cpu_dec(*(prog->active));
|
|
migrate_enable();
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
static u64 notrace __bpf_prog_enter_lsm_cgroup(struct bpf_prog *prog,
|
|
struct bpf_tramp_run_ctx *run_ctx)
|
|
__acquires(RCU)
|
|
{
|
|
/* Runtime stats are exported via actual BPF_LSM_CGROUP
|
|
* programs, not the shims.
|
|
*/
|
|
rcu_read_lock();
|
|
migrate_disable();
|
|
|
|
run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
|
|
|
|
return NO_START_TIME;
|
|
}
|
|
|
|
static void notrace __bpf_prog_exit_lsm_cgroup(struct bpf_prog *prog, u64 start,
|
|
struct bpf_tramp_run_ctx *run_ctx)
|
|
__releases(RCU)
|
|
{
|
|
bpf_reset_run_ctx(run_ctx->saved_run_ctx);
|
|
|
|
migrate_enable();
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
u64 notrace __bpf_prog_enter_sleepable_recur(struct bpf_prog *prog,
|
|
struct bpf_tramp_run_ctx *run_ctx)
|
|
{
|
|
rcu_read_lock_trace();
|
|
migrate_disable();
|
|
might_fault();
|
|
|
|
if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
|
|
bpf_prog_inc_misses_counter(prog);
|
|
return 0;
|
|
}
|
|
|
|
run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
|
|
|
|
return bpf_prog_start_time();
|
|
}
|
|
|
|
void notrace __bpf_prog_exit_sleepable_recur(struct bpf_prog *prog, u64 start,
|
|
struct bpf_tramp_run_ctx *run_ctx)
|
|
{
|
|
bpf_reset_run_ctx(run_ctx->saved_run_ctx);
|
|
|
|
update_prog_stats(prog, start);
|
|
this_cpu_dec(*(prog->active));
|
|
migrate_enable();
|
|
rcu_read_unlock_trace();
|
|
}
|
|
|
|
static u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog,
|
|
struct bpf_tramp_run_ctx *run_ctx)
|
|
{
|
|
rcu_read_lock_trace();
|
|
migrate_disable();
|
|
might_fault();
|
|
|
|
run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
|
|
|
|
return bpf_prog_start_time();
|
|
}
|
|
|
|
static void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start,
|
|
struct bpf_tramp_run_ctx *run_ctx)
|
|
{
|
|
bpf_reset_run_ctx(run_ctx->saved_run_ctx);
|
|
|
|
update_prog_stats(prog, start);
|
|
migrate_enable();
|
|
rcu_read_unlock_trace();
|
|
}
|
|
|
|
static u64 notrace __bpf_prog_enter(struct bpf_prog *prog,
|
|
struct bpf_tramp_run_ctx *run_ctx)
|
|
__acquires(RCU)
|
|
{
|
|
rcu_read_lock();
|
|
migrate_disable();
|
|
|
|
run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
|
|
|
|
return bpf_prog_start_time();
|
|
}
|
|
|
|
static void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start,
|
|
struct bpf_tramp_run_ctx *run_ctx)
|
|
__releases(RCU)
|
|
{
|
|
bpf_reset_run_ctx(run_ctx->saved_run_ctx);
|
|
|
|
update_prog_stats(prog, start);
|
|
migrate_enable();
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
void notrace __bpf_tramp_enter(struct bpf_tramp_image *tr)
|
|
{
|
|
percpu_ref_get(&tr->pcref);
|
|
}
|
|
|
|
void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr)
|
|
{
|
|
percpu_ref_put(&tr->pcref);
|
|
}
|
|
|
|
bpf_trampoline_enter_t bpf_trampoline_enter(const struct bpf_prog *prog)
|
|
{
|
|
bool sleepable = prog->aux->sleepable;
|
|
|
|
if (bpf_prog_check_recur(prog))
|
|
return sleepable ? __bpf_prog_enter_sleepable_recur :
|
|
__bpf_prog_enter_recur;
|
|
|
|
if (resolve_prog_type(prog) == BPF_PROG_TYPE_LSM &&
|
|
prog->expected_attach_type == BPF_LSM_CGROUP)
|
|
return __bpf_prog_enter_lsm_cgroup;
|
|
|
|
return sleepable ? __bpf_prog_enter_sleepable : __bpf_prog_enter;
|
|
}
|
|
|
|
bpf_trampoline_exit_t bpf_trampoline_exit(const struct bpf_prog *prog)
|
|
{
|
|
bool sleepable = prog->aux->sleepable;
|
|
|
|
if (bpf_prog_check_recur(prog))
|
|
return sleepable ? __bpf_prog_exit_sleepable_recur :
|
|
__bpf_prog_exit_recur;
|
|
|
|
if (resolve_prog_type(prog) == BPF_PROG_TYPE_LSM &&
|
|
prog->expected_attach_type == BPF_LSM_CGROUP)
|
|
return __bpf_prog_exit_lsm_cgroup;
|
|
|
|
return sleepable ? __bpf_prog_exit_sleepable : __bpf_prog_exit;
|
|
}
|
|
|
|
int __weak
|
|
arch_prepare_bpf_trampoline(struct bpf_tramp_image *tr, void *image, void *image_end,
|
|
const struct btf_func_model *m, u32 flags,
|
|
struct bpf_tramp_links *tlinks,
|
|
void *orig_call)
|
|
{
|
|
return -ENOTSUPP;
|
|
}
|
|
|
|
static int __init init_trampolines(void)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < TRAMPOLINE_TABLE_SIZE; i++)
|
|
INIT_HLIST_HEAD(&trampoline_table[i]);
|
|
return 0;
|
|
}
|
|
late_initcall(init_trampolines);
|