1 // SPDX-License-Identifier: GPL-2.0 2 /* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */ 3 #include <vmlinux.h> 4 #include <bpf/bpf_helpers.h> 5 #include <bpf/bpf_tracing.h> 6 #include "bpf_misc.h" 7 8 char _license[] SEC("license") = "GPL"; 9 10 struct { 11 __uint(type, BPF_MAP_TYPE_CGRP_STORAGE); 12 __uint(map_flags, BPF_F_NO_PREALLOC); 13 __type(key, int); 14 __type(value, long); 15 } map_a SEC(".maps"); 16 17 __s32 target_pid; 18 __u64 cgroup_id; 19 int target_hid; 20 bool is_cgroup1; 21 22 struct cgroup *bpf_task_get_cgroup1(struct task_struct *task, int hierarchy_id) __ksym; 23 void bpf_cgroup_release(struct cgroup *cgrp) __ksym; 24 void bpf_rcu_read_lock(void) __ksym; 25 void bpf_rcu_read_unlock(void) __ksym; 26 27 SEC("?iter.s/cgroup") 28 int cgroup_iter(struct bpf_iter__cgroup *ctx) 29 { 30 struct cgroup *cgrp = ctx->cgroup; 31 long *ptr; 32 33 if (cgrp == NULL) 34 return 0; 35 36 ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0, 37 BPF_LOCAL_STORAGE_GET_F_CREATE); 38 if (ptr) 39 cgroup_id = cgrp->kn->id; 40 return 0; 41 } 42 43 static void __no_rcu_lock(struct cgroup *cgrp) 44 { 45 long *ptr; 46 47 /* Note that trace rcu is held in sleepable prog, so we can use 48 * bpf_cgrp_storage_get() in sleepable prog. 49 */ 50 ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0, 51 BPF_LOCAL_STORAGE_GET_F_CREATE); 52 if (ptr) 53 cgroup_id = cgrp->kn->id; 54 } 55 56 SEC("?fentry.s/" SYS_PREFIX "sys_getpgid") 57 int cgrp1_no_rcu_lock(void *ctx) 58 { 59 struct task_struct *task; 60 struct cgroup *cgrp; 61 62 task = bpf_get_current_task_btf(); 63 if (task->pid != target_pid) 64 return 0; 65 66 /* bpf_task_get_cgroup1 can work in sleepable prog */ 67 cgrp = bpf_task_get_cgroup1(task, target_hid); 68 if (!cgrp) 69 return 0; 70 71 __no_rcu_lock(cgrp); 72 bpf_cgroup_release(cgrp); 73 return 0; 74 } 75 76 SEC("?fentry.s/" SYS_PREFIX "sys_getpgid") 77 int no_rcu_lock(void *ctx) 78 { 79 struct task_struct *task; 80 81 task = bpf_get_current_task_btf(); 82 if (task->pid != target_pid) 83 return 0; 84 85 /* task->cgroups is untrusted in sleepable prog outside of RCU CS */ 86 __no_rcu_lock(task->cgroups->dfl_cgrp); 87 return 0; 88 } 89 90 SEC("?fentry.s/" SYS_PREFIX "sys_getpgid") 91 int yes_rcu_lock(void *ctx) 92 { 93 struct task_struct *task; 94 struct cgroup *cgrp; 95 long *ptr; 96 97 task = bpf_get_current_task_btf(); 98 if (task->pid != target_pid) 99 return 0; 100 101 if (is_cgroup1) { 102 bpf_rcu_read_lock(); 103 cgrp = bpf_task_get_cgroup1(task, target_hid); 104 if (!cgrp) { 105 bpf_rcu_read_unlock(); 106 return 0; 107 } 108 109 ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0, BPF_LOCAL_STORAGE_GET_F_CREATE); 110 if (ptr) 111 cgroup_id = cgrp->kn->id; 112 bpf_cgroup_release(cgrp); 113 bpf_rcu_read_unlock(); 114 return 0; 115 } 116 117 bpf_rcu_read_lock(); 118 cgrp = task->cgroups->dfl_cgrp; 119 /* cgrp is trusted under RCU CS */ 120 ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0, BPF_LOCAL_STORAGE_GET_F_CREATE); 121 if (ptr) 122 cgroup_id = cgrp->kn->id; 123 bpf_rcu_read_unlock(); 124 return 0; 125 } 126