1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/sched/signal.h> 3 #include <linux/errno.h> 4 #include <linux/dcache.h> 5 #include <linux/path.h> 6 #include <linux/fdtable.h> 7 #include <linux/namei.h> 8 #include <linux/pid.h> 9 #include <linux/ptrace.h> 10 #include <linux/bitmap.h> 11 #include <linux/security.h> 12 #include <linux/file.h> 13 #include <linux/seq_file.h> 14 #include <linux/fs.h> 15 #include <linux/filelock.h> 16 17 #include <linux/proc_fs.h> 18 19 #include "../mount.h" 20 #include "internal.h" 21 #include "fd.h" 22 23 static int seq_show(struct seq_file *m, void *v) 24 { 25 struct files_struct *files = NULL; 26 int f_flags = 0, ret = -ENOENT; 27 struct file *file = NULL; 28 struct task_struct *task; 29 30 task = get_proc_task(m->private); 31 if (!task) 32 return -ENOENT; 33 34 task_lock(task); 35 files = task->files; 36 if (files) { 37 unsigned int fd = proc_fd(m->private); 38 39 spin_lock(&files->file_lock); 40 file = files_lookup_fd_locked(files, fd); 41 if (file) { 42 f_flags = file->f_flags; 43 if (close_on_exec(fd, files)) 44 f_flags |= O_CLOEXEC; 45 46 get_file(file); 47 ret = 0; 48 } 49 spin_unlock(&files->file_lock); 50 } 51 task_unlock(task); 52 put_task_struct(task); 53 54 if (ret) 55 return ret; 56 57 seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\nino:\t%lu\n", 58 (long long)file->f_pos, f_flags, 59 real_mount(file->f_path.mnt)->mnt_id, 60 file_inode(file)->i_ino); 61 62 /* show_fd_locks() never deferences files so a stale value is safe */ 63 show_fd_locks(m, file, files); 64 if (seq_has_overflowed(m)) 65 goto out; 66 67 if (file->f_op->show_fdinfo) 68 file->f_op->show_fdinfo(m, file); 69 70 out: 71 fput(file); 72 return 0; 73 } 74 75 static int seq_fdinfo_open(struct inode *inode, struct file *file) 76 { 77 return single_open(file, seq_show, inode); 78 } 79 80 /** 81 * Shared /proc/pid/fdinfo and /proc/pid/fdinfo/fd permission helper to ensure 82 * that the current task has PTRACE_MODE_READ in addition to the normal 83 * POSIX-like checks. 84 */ 85 static int proc_fdinfo_permission(struct mnt_idmap *idmap, struct inode *inode, 86 int mask) 87 { 88 bool allowed = false; 89 struct task_struct *task = get_proc_task(inode); 90 91 if (!task) 92 return -ESRCH; 93 94 allowed = ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS); 95 put_task_struct(task); 96 97 if (!allowed) 98 return -EACCES; 99 100 return generic_permission(idmap, inode, mask); 101 } 102 103 static const struct inode_operations proc_fdinfo_file_inode_operations = { 104 .permission = proc_fdinfo_permission, 105 .setattr = proc_setattr, 106 }; 107 108 static const struct file_operations proc_fdinfo_file_operations = { 109 .open = seq_fdinfo_open, 110 .read = seq_read, 111 .llseek = seq_lseek, 112 .release = single_release, 113 }; 114 115 static bool tid_fd_mode(struct task_struct *task, unsigned fd, fmode_t *mode) 116 { 117 struct file *file; 118 119 rcu_read_lock(); 120 file = task_lookup_fdget_rcu(task, fd); 121 rcu_read_unlock(); 122 if (file) { 123 *mode = file->f_mode; 124 fput(file); 125 } 126 return !!file; 127 } 128 129 static void tid_fd_update_inode(struct task_struct *task, struct inode *inode, 130 fmode_t f_mode) 131 { 132 task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid); 133 134 if (S_ISLNK(inode->i_mode)) { 135 unsigned i_mode = S_IFLNK; 136 if (f_mode & FMODE_READ) 137 i_mode |= S_IRUSR | S_IXUSR; 138 if (f_mode & FMODE_WRITE) 139 i_mode |= S_IWUSR | S_IXUSR; 140 inode->i_mode = i_mode; 141 } 142 security_task_to_inode(task, inode); 143 } 144 145 static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags) 146 { 147 struct task_struct *task; 148 struct inode *inode; 149 unsigned int fd; 150 151 if (flags & LOOKUP_RCU) 152 return -ECHILD; 153 154 inode = d_inode(dentry); 155 task = get_proc_task(inode); 156 fd = proc_fd(inode); 157 158 if (task) { 159 fmode_t f_mode; 160 if (tid_fd_mode(task, fd, &f_mode)) { 161 tid_fd_update_inode(task, inode, f_mode); 162 put_task_struct(task); 163 return 1; 164 } 165 put_task_struct(task); 166 } 167 return 0; 168 } 169 170 static const struct dentry_operations tid_fd_dentry_operations = { 171 .d_revalidate = tid_fd_revalidate, 172 .d_delete = pid_delete_dentry, 173 }; 174 175 static int proc_fd_link(struct dentry *dentry, struct path *path) 176 { 177 struct task_struct *task; 178 int ret = -ENOENT; 179 180 task = get_proc_task(d_inode(dentry)); 181 if (task) { 182 unsigned int fd = proc_fd(d_inode(dentry)); 183 struct file *fd_file; 184 185 fd_file = fget_task(task, fd); 186 if (fd_file) { 187 *path = fd_file->f_path; 188 path_get(&fd_file->f_path); 189 ret = 0; 190 fput(fd_file); 191 } 192 put_task_struct(task); 193 } 194 195 return ret; 196 } 197 198 struct fd_data { 199 fmode_t mode; 200 unsigned fd; 201 }; 202 203 static struct dentry *proc_fd_instantiate(struct dentry *dentry, 204 struct task_struct *task, const void *ptr) 205 { 206 const struct fd_data *data = ptr; 207 struct proc_inode *ei; 208 struct inode *inode; 209 210 inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK); 211 if (!inode) 212 return ERR_PTR(-ENOENT); 213 214 ei = PROC_I(inode); 215 ei->fd = data->fd; 216 217 inode->i_op = &proc_pid_link_inode_operations; 218 inode->i_size = 64; 219 220 ei->op.proc_get_link = proc_fd_link; 221 tid_fd_update_inode(task, inode, data->mode); 222 223 d_set_d_op(dentry, &tid_fd_dentry_operations); 224 return d_splice_alias(inode, dentry); 225 } 226 227 static struct dentry *proc_lookupfd_common(struct inode *dir, 228 struct dentry *dentry, 229 instantiate_t instantiate) 230 { 231 struct task_struct *task = get_proc_task(dir); 232 struct fd_data data = {.fd = name_to_int(&dentry->d_name)}; 233 struct dentry *result = ERR_PTR(-ENOENT); 234 235 if (!task) 236 goto out_no_task; 237 if (data.fd == ~0U) 238 goto out; 239 if (!tid_fd_mode(task, data.fd, &data.mode)) 240 goto out; 241 242 result = instantiate(dentry, task, &data); 243 out: 244 put_task_struct(task); 245 out_no_task: 246 return result; 247 } 248 249 static int proc_readfd_common(struct file *file, struct dir_context *ctx, 250 instantiate_t instantiate) 251 { 252 struct task_struct *p = get_proc_task(file_inode(file)); 253 unsigned int fd; 254 255 if (!p) 256 return -ENOENT; 257 258 if (!dir_emit_dots(file, ctx)) 259 goto out; 260 261 rcu_read_lock(); 262 for (fd = ctx->pos - 2;; fd++) { 263 struct file *f; 264 struct fd_data data; 265 char name[10 + 1]; 266 unsigned int len; 267 268 f = task_lookup_next_fdget_rcu(p, &fd); 269 ctx->pos = fd + 2LL; 270 if (!f) 271 break; 272 data.mode = f->f_mode; 273 rcu_read_unlock(); 274 fput(f); 275 data.fd = fd; 276 277 len = snprintf(name, sizeof(name), "%u", fd); 278 if (!proc_fill_cache(file, ctx, 279 name, len, instantiate, p, 280 &data)) 281 goto out; 282 cond_resched(); 283 rcu_read_lock(); 284 } 285 rcu_read_unlock(); 286 out: 287 put_task_struct(p); 288 return 0; 289 } 290 291 static int proc_readfd_count(struct inode *inode, loff_t *count) 292 { 293 struct task_struct *p = get_proc_task(inode); 294 struct fdtable *fdt; 295 296 if (!p) 297 return -ENOENT; 298 299 task_lock(p); 300 if (p->files) { 301 rcu_read_lock(); 302 303 fdt = files_fdtable(p->files); 304 *count = bitmap_weight(fdt->open_fds, fdt->max_fds); 305 306 rcu_read_unlock(); 307 } 308 task_unlock(p); 309 310 put_task_struct(p); 311 312 return 0; 313 } 314 315 static int proc_readfd(struct file *file, struct dir_context *ctx) 316 { 317 return proc_readfd_common(file, ctx, proc_fd_instantiate); 318 } 319 320 const struct file_operations proc_fd_operations = { 321 .read = generic_read_dir, 322 .iterate_shared = proc_readfd, 323 .llseek = generic_file_llseek, 324 }; 325 326 static struct dentry *proc_lookupfd(struct inode *dir, struct dentry *dentry, 327 unsigned int flags) 328 { 329 return proc_lookupfd_common(dir, dentry, proc_fd_instantiate); 330 } 331 332 /* 333 * /proc/pid/fd needs a special permission handler so that a process can still 334 * access /proc/self/fd after it has executed a setuid(). 335 */ 336 int proc_fd_permission(struct mnt_idmap *idmap, 337 struct inode *inode, int mask) 338 { 339 struct task_struct *p; 340 int rv; 341 342 rv = generic_permission(&nop_mnt_idmap, inode, mask); 343 if (rv == 0) 344 return rv; 345 346 rcu_read_lock(); 347 p = pid_task(proc_pid(inode), PIDTYPE_PID); 348 if (p && same_thread_group(p, current)) 349 rv = 0; 350 rcu_read_unlock(); 351 352 return rv; 353 } 354 355 static int proc_fd_getattr(struct mnt_idmap *idmap, 356 const struct path *path, struct kstat *stat, 357 u32 request_mask, unsigned int query_flags) 358 { 359 struct inode *inode = d_inode(path->dentry); 360 int rv = 0; 361 362 generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat); 363 364 /* If it's a directory, put the number of open fds there */ 365 if (S_ISDIR(inode->i_mode)) { 366 rv = proc_readfd_count(inode, &stat->size); 367 if (rv < 0) 368 return rv; 369 } 370 371 return rv; 372 } 373 374 const struct inode_operations proc_fd_inode_operations = { 375 .lookup = proc_lookupfd, 376 .permission = proc_fd_permission, 377 .getattr = proc_fd_getattr, 378 .setattr = proc_setattr, 379 }; 380 381 static struct dentry *proc_fdinfo_instantiate(struct dentry *dentry, 382 struct task_struct *task, const void *ptr) 383 { 384 const struct fd_data *data = ptr; 385 struct proc_inode *ei; 386 struct inode *inode; 387 388 inode = proc_pid_make_inode(dentry->d_sb, task, S_IFREG | S_IRUGO); 389 if (!inode) 390 return ERR_PTR(-ENOENT); 391 392 ei = PROC_I(inode); 393 ei->fd = data->fd; 394 395 inode->i_op = &proc_fdinfo_file_inode_operations; 396 397 inode->i_fop = &proc_fdinfo_file_operations; 398 tid_fd_update_inode(task, inode, 0); 399 400 d_set_d_op(dentry, &tid_fd_dentry_operations); 401 return d_splice_alias(inode, dentry); 402 } 403 404 static struct dentry * 405 proc_lookupfdinfo(struct inode *dir, struct dentry *dentry, unsigned int flags) 406 { 407 return proc_lookupfd_common(dir, dentry, proc_fdinfo_instantiate); 408 } 409 410 static int proc_readfdinfo(struct file *file, struct dir_context *ctx) 411 { 412 return proc_readfd_common(file, ctx, 413 proc_fdinfo_instantiate); 414 } 415 416 const struct inode_operations proc_fdinfo_inode_operations = { 417 .lookup = proc_lookupfdinfo, 418 .permission = proc_fdinfo_permission, 419 .setattr = proc_setattr, 420 }; 421 422 const struct file_operations proc_fdinfo_operations = { 423 .read = generic_read_dir, 424 .iterate_shared = proc_readfdinfo, 425 .llseek = generic_file_llseek, 426 }; 427