kernel/bpf/task_iter.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Copyright (c) 2020 Facebook */
   3
   4 #include <linux/init.h>
   5 #include <linux/namei.h>
   6 #include <linux/pid_namespace.h>
   7 #include <linux/fs.h>
   8 #include <linux/fdtable.h>
   9 #include <linux/filter.h>
  10
  11 struct bpf_iter_seq_task_common {
  12         struct pid_namespace *ns;
  13 };
  14
  15 struct bpf_iter_seq_task_info {
  16         /* The first field must be struct bpf_iter_seq_task_common.
  17          * this is assumed by {init, fini}_seq_pidns() callback functions.
  18          */
  19         struct bpf_iter_seq_task_common common;
  20         u32 tid;
  21 };
  22
  23 static struct task_struct *task_seq_get_next(struct pid_namespace *ns,
  24                                              u32 *tid)
  25 {
  26         struct task_struct *task = NULL;
  27         struct pid *pid;
  28
  29         rcu_read_lock();
  30 retry:
  31         pid = idr_get_next(&ns->idr, tid);
  32         if (pid) {
  33                 task = get_pid_task(pid, PIDTYPE_PID);
  34                 if (!task) {
  35                         ++*tid;
  36                         goto retry;
  37                 }
  38         }
  39         rcu_read_unlock();
  40
  41         return task;
  42 }
  43
  44 static void *task_seq_start(struct seq_file *seq, loff_t *pos)
  45 {
  46         struct bpf_iter_seq_task_info *info = seq->private;
  47         struct task_struct *task;
  48
  49         task = task_seq_get_next(info->common.ns, &info->tid);
  50         if (!task)
  51                 return NULL;
  52
  53         ++*pos;
  54         return task;
  55 }
  56
  57 static void *task_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  58 {
  59         struct bpf_iter_seq_task_info *info = seq->private;
  60         struct task_struct *task;
  61
  62         ++*pos;
  63         ++info->tid;
  64         put_task_struct((struct task_struct *)v);
  65         task = task_seq_get_next(info->common.ns, &info->tid);
  66         if (!task)
  67                 return NULL;
  68
  69         return task;
  70 }
  71
  72 struct bpf_iter__task {
  73         __bpf_md_ptr(struct bpf_iter_meta *, meta);
  74         __bpf_md_ptr(struct task_struct *, task);
  75 };
  76
  77 DEFINE_BPF_ITER_FUNC(task, struct bpf_iter_meta *meta, struct task_struct *task)
  78
  79 static int __task_seq_show(struct seq_file *seq, struct task_struct *task,
  80                            bool in_stop)
  81 {
  82         struct bpf_iter_meta meta;
  83         struct bpf_iter__task ctx;
  84         struct bpf_prog *prog;
  85
  86         meta.seq = seq;
  87         prog = bpf_iter_get_info(&meta, in_stop);
  88         if (!prog)
  89                 return 0;
  90
  91         meta.seq = seq;
  92         ctx.meta = &meta;
  93         ctx.task = task;
  94         return bpf_iter_run_prog(prog, &ctx);
  95 }
  96
  97 static int task_seq_show(struct seq_file *seq, void *v)
  98 {
  99         return __task_seq_show(seq, v, false);
 100 }
 101
 102 static void task_seq_stop(struct seq_file *seq, void *v)
 103 {
 104         if (!v)
 105                 (void)__task_seq_show(seq, v, true);
 106         else
 107                 put_task_struct((struct task_struct *)v);
 108 }
 109
 110 static const struct seq_operations task_seq_ops = {
 111         .start  = task_seq_start,
 112         .next   = task_seq_next,
 113         .stop   = task_seq_stop,
 114         .show   = task_seq_show,
 115 };
 116
 117 struct bpf_iter_seq_task_file_info {
 118         /* The first field must be struct bpf_iter_seq_task_common.
 119          * this is assumed by {init, fini}_seq_pidns() callback functions.
 120          */
 121         struct bpf_iter_seq_task_common common;
 122         struct task_struct *task;
 123         struct files_struct *files;
 124         u32 tid;
 125         u32 fd;
 126 };
 127
 128 static struct file *
 129 task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info,
 130                        struct task_struct **task, struct files_struct **fstruct)
 131 {
 132         struct pid_namespace *ns = info->common.ns;
 133         u32 curr_tid = info->tid, max_fds;
 134         struct files_struct *curr_files;
 135         struct task_struct *curr_task;
 136         int curr_fd = info->fd;
 137
 138         /* If this function returns a non-NULL file object,
 139          * it held a reference to the task/files_struct/file.
 140          * Otherwise, it does not hold any reference.
 141          */
 142 again:
 143         if (*task) {
 144                 curr_task = *task;
 145                 curr_files = *fstruct;
 146                 curr_fd = info->fd;
 147         } else {
 148                 curr_task = task_seq_get_next(ns, &curr_tid);
 149                 if (!curr_task)
 150                         return NULL;
 151
 152                 curr_files = get_files_struct(curr_task);
 153                 if (!curr_files) {
 154                         put_task_struct(curr_task);
 155                         curr_tid = ++(info->tid);
 156                         info->fd = 0;
 157                         goto again;
 158                 }
 159
 160                 /* set *fstruct, *task and info->tid */
 161                 *fstruct = curr_files;
 162                 *task = curr_task;
 163                 if (curr_tid == info->tid) {
 164                         curr_fd = info->fd;
 165                 } else {
 166                         info->tid = curr_tid;
 167                         curr_fd = 0;
 168                 }
 169         }
 170
 171         rcu_read_lock();
 172         max_fds = files_fdtable(curr_files)->max_fds;
 173         for (; curr_fd < max_fds; curr_fd++) {
 174                 struct file *f;
 175
 176                 f = fcheck_files(curr_files, curr_fd);
 177                 if (!f)
 178                         continue;
 179
 180                 /* set info->fd */
 181                 info->fd = curr_fd;
 182                 get_file(f);
 183                 rcu_read_unlock();
 184                 return f;
 185         }
 186
 187         /* the current task is done, go to the next task */
 188         rcu_read_unlock();
 189         put_files_struct(curr_files);
 190         put_task_struct(curr_task);
 191         *task = NULL;
 192         *fstruct = NULL;
 193         info->fd = 0;
 194         curr_tid = ++(info->tid);
 195         goto again;
 196 }
 197
 198 static void *task_file_seq_start(struct seq_file *seq, loff_t *pos)
 199 {
 200         struct bpf_iter_seq_task_file_info *info = seq->private;
 201         struct files_struct *files = NULL;
 202         struct task_struct *task = NULL;
 203         struct file *file;
 204
 205         file = task_file_seq_get_next(info, &task, &files);
 206         if (!file) {
 207                 info->files = NULL;
 208                 info->task = NULL;
 209                 return NULL;
 210         }
 211
 212         ++*pos;
 213         info->task = task;
 214         info->files = files;
 215
 216         return file;
 217 }
 218
 219 static void *task_file_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 220 {
 221         struct bpf_iter_seq_task_file_info *info = seq->private;
 222         struct files_struct *files = info->files;
 223         struct task_struct *task = info->task;
 224         struct file *file;
 225
 226         ++*pos;
 227         ++info->fd;
 228         fput((struct file *)v);
 229         file = task_file_seq_get_next(info, &task, &files);
 230         if (!file) {
 231                 info->files = NULL;
 232                 info->task = NULL;
 233                 return NULL;
 234         }
 235
 236         info->task = task;
 237         info->files = files;
 238
 239         return file;
 240 }
 241
 242 struct bpf_iter__task_file {
 243         __bpf_md_ptr(struct bpf_iter_meta *, meta);
 244         __bpf_md_ptr(struct task_struct *, task);
 245         u32 fd __aligned(8);
 246         __bpf_md_ptr(struct file *, file);
 247 };
 248
 249 DEFINE_BPF_ITER_FUNC(task_file, struct bpf_iter_meta *meta,
 250                      struct task_struct *task, u32 fd,
 251                      struct file *file)
 252
 253 static int __task_file_seq_show(struct seq_file *seq, struct file *file,
 254                                 bool in_stop)
 255 {
 256         struct bpf_iter_seq_task_file_info *info = seq->private;
 257         struct bpf_iter__task_file ctx;
 258         struct bpf_iter_meta meta;
 259         struct bpf_prog *prog;
 260
 261         meta.seq = seq;
 262         prog = bpf_iter_get_info(&meta, in_stop);
 263         if (!prog)
 264                 return 0;
 265
 266         ctx.meta = &meta;
 267         ctx.task = info->task;
 268         ctx.fd = info->fd;
 269         ctx.file = file;
 270         return bpf_iter_run_prog(prog, &ctx);
 271 }
 272
 273 static int task_file_seq_show(struct seq_file *seq, void *v)
 274 {
 275         return __task_file_seq_show(seq, v, false);
 276 }
 277
 278 static void task_file_seq_stop(struct seq_file *seq, void *v)
 279 {
 280         struct bpf_iter_seq_task_file_info *info = seq->private;
 281
 282         if (!v) {
 283                 (void)__task_file_seq_show(seq, v, true);
 284         } else {
 285                 fput((struct file *)v);
 286                 put_files_struct(info->files);
 287                 put_task_struct(info->task);
 288                 info->files = NULL;
 289                 info->task = NULL;
 290         }
 291 }
 292
 293 static int init_seq_pidns(void *priv_data)
 294 {
 295         struct bpf_iter_seq_task_common *common = priv_data;
 296
 297         common->ns = get_pid_ns(task_active_pid_ns(current));
 298         return 0;
 299 }
 300
 301 static void fini_seq_pidns(void *priv_data)
 302 {
 303         struct bpf_iter_seq_task_common *common = priv_data;
 304
 305         put_pid_ns(common->ns);
 306 }
 307
 308 static const struct seq_operations task_file_seq_ops = {
 309         .start  = task_file_seq_start,
 310         .next   = task_file_seq_next,
 311         .stop   = task_file_seq_stop,
 312         .show   = task_file_seq_show,
 313 };
 314
 315 static const struct bpf_iter_reg task_reg_info = {
 316         .target                 = "task",
 317         .seq_ops                = &task_seq_ops,
 318         .init_seq_private       = init_seq_pidns,
 319         .fini_seq_private       = fini_seq_pidns,
 320         .seq_priv_size          = sizeof(struct bpf_iter_seq_task_info),
 321         .ctx_arg_info_size      = 1,
 322         .ctx_arg_info           = {
 323                 { offsetof(struct bpf_iter__task, task),
 324                   PTR_TO_BTF_ID_OR_NULL },
 325         },
 326 };
 327
 328 static const struct bpf_iter_reg task_file_reg_info = {
 329         .target                 = "task_file",
 330         .seq_ops                = &task_file_seq_ops,
 331         .init_seq_private       = init_seq_pidns,
 332         .fini_seq_private       = fini_seq_pidns,
 333         .seq_priv_size          = sizeof(struct bpf_iter_seq_task_file_info),
 334         .ctx_arg_info_size      = 2,
 335         .ctx_arg_info           = {
 336                 { offsetof(struct bpf_iter__task_file, task),
 337                   PTR_TO_BTF_ID_OR_NULL },
 338                 { offsetof(struct bpf_iter__task_file, file),
 339                   PTR_TO_BTF_ID_OR_NULL },
 340         },
 341 };
 342
 343 static int __init task_iter_init(void)
 344 {
 345         int ret;
 346
 347         ret = bpf_iter_reg_target(&task_reg_info);
 348         if (ret)
 349                 return ret;
 350
 351         return bpf_iter_reg_target(&task_file_reg_info);
 352 }
 353 late_initcall(task_iter_init);