1 // SPDX-License-Identifier: GPL-2.0 2 /* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */ 3 4 #include "bpf_iter.h" 5 #include <bpf/bpf_helpers.h> 6 #include <bpf/bpf_tracing.h> 7 #include "bpf_misc.h" 8 9 char _license[] SEC("license") = "GPL"; 10 11 struct { 12 __uint(type, BPF_MAP_TYPE_CGRP_STORAGE); 13 __uint(map_flags, BPF_F_NO_PREALLOC); 14 __type(key, int); 15 __type(value, long); 16 } map_a SEC(".maps"); 17 18 __s32 target_pid; 19 __u64 cgroup_id; 20 int target_hid; 21 bool is_cgroup1; 22 23 struct cgroup *bpf_task_get_cgroup1(struct task_struct *task, int hierarchy_id) __ksym; 24 void bpf_cgroup_release(struct cgroup *cgrp) __ksym; 25 void bpf_rcu_read_lock(void) __ksym; 26 void bpf_rcu_read_unlock(void) __ksym; 27 28 SEC("?iter.s/cgroup") 29 int cgroup_iter(struct bpf_iter__cgroup *ctx) 30 { 31 struct cgroup *cgrp = ctx->cgroup; 32 long *ptr; 33 34 if (cgrp == NULL) 35 return 0; 36 37 ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0, 38 BPF_LOCAL_STORAGE_GET_F_CREATE); 39 if (ptr) 40 cgroup_id = cgrp->kn->id; 41 return 0; 42 } 43 44 static void __no_rcu_lock(struct cgroup *cgrp) 45 { 46 long *ptr; 47 48 /* Note that trace rcu is held in sleepable prog, so we can use 49 * bpf_cgrp_storage_get() in sleepable prog. 50 */ 51 ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0, 52 BPF_LOCAL_STORAGE_GET_F_CREATE); 53 if (ptr) 54 cgroup_id = cgrp->kn->id; 55 } 56 57 SEC("?fentry.s/" SYS_PREFIX "sys_getpgid") 58 int cgrp1_no_rcu_lock(void *ctx) 59 { 60 struct task_struct *task; 61 struct cgroup *cgrp; 62 63 task = bpf_get_current_task_btf(); 64 if (task->pid != target_pid) 65 return 0; 66 67 /* bpf_task_get_cgroup1 can work in sleepable prog */ 68 cgrp = bpf_task_get_cgroup1(task, target_hid); 69 if (!cgrp) 70 return 0; 71 72 __no_rcu_lock(cgrp); 73 bpf_cgroup_release(cgrp); 74 return 0; 75 } 76 77 SEC("?fentry.s/" SYS_PREFIX "sys_getpgid") 78 int no_rcu_lock(void *ctx) 79 { 80 struct task_struct *task; 81 82 task = bpf_get_current_task_btf(); 83 if (task->pid != target_pid) 84 return 0; 85 86 /* task->cgroups is untrusted in sleepable prog outside of RCU CS */ 87 __no_rcu_lock(task->cgroups->dfl_cgrp); 88 return 0; 89 } 90 91 SEC("?fentry.s/" SYS_PREFIX "sys_getpgid") 92 int yes_rcu_lock(void *ctx) 93 { 94 struct task_struct *task; 95 struct cgroup *cgrp; 96 long *ptr; 97 98 task = bpf_get_current_task_btf(); 99 if (task->pid != target_pid) 100 return 0; 101 102 if (is_cgroup1) { 103 bpf_rcu_read_lock(); 104 cgrp = bpf_task_get_cgroup1(task, target_hid); 105 if (!cgrp) { 106 bpf_rcu_read_unlock(); 107 return 0; 108 } 109 110 ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0, BPF_LOCAL_STORAGE_GET_F_CREATE); 111 if (ptr) 112 cgroup_id = cgrp->kn->id; 113 bpf_cgroup_release(cgrp); 114 bpf_rcu_read_unlock(); 115 return 0; 116 } 117 118 bpf_rcu_read_lock(); 119 cgrp = task->cgroups->dfl_cgrp; 120 /* cgrp is trusted under RCU CS */ 121 ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0, BPF_LOCAL_STORAGE_GET_F_CREATE); 122 if (ptr) 123 cgroup_id = cgrp->kn->id; 124 bpf_rcu_read_unlock(); 125 return 0; 126 } 127