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 struct fdtable *fdt = files_fdtable(files); 43 44 f_flags = file->f_flags; 45 if (close_on_exec(fd, fdt)) 46 f_flags |= O_CLOEXEC; 47 48 get_file(file); 49 ret = 0; 50 } 51 spin_unlock(&files->file_lock); 52 } 53 task_unlock(task); 54 put_task_struct(task); 55 56 if (ret) 57 return ret; 58 59 seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\nino:\t%lu\n", 60 (long long)file->f_pos, f_flags, 61 real_mount(file->f_path.mnt)->mnt_id, 62 file_inode(file)->i_ino); 63 64 /* show_fd_locks() never deferences files so a stale value is safe */ 65 show_fd_locks(m, file, files); 66 if (seq_has_overflowed(m)) 67 goto out; 68 69 if (file->f_op->show_fdinfo) 70 file->f_op->show_fdinfo(m, file); 71 72 out: 73 fput(file); 74 return 0; 75 } 76 77 static int seq_fdinfo_open(struct inode *inode, struct file *file) 78 { 79 return single_open(file, seq_show, inode); 80 } 81 82 /** 83 * Shared /proc/pid/fdinfo and /proc/pid/fdinfo/fd permission helper to ensure 84 * that the current task has PTRACE_MODE_READ in addition to the normal 85 * POSIX-like checks. 86 */ 87 static int proc_fdinfo_permission(struct mnt_idmap *idmap, struct inode *inode, 88 int mask) 89 { 90 bool allowed = false; 91 struct task_struct *task = get_proc_task(inode); 92 93 if (!task) 94 return -ESRCH; 95 96 allowed = ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS); 97 put_task_struct(task); 98 99 if (!allowed) 100 return -EACCES; 101 102 return generic_permission(idmap, inode, mask); 103 } 104 105 static const struct inode_operations proc_fdinfo_file_inode_operations = { 106 .permission = proc_fdinfo_permission, 107 .setattr = proc_setattr, 108 }; 109 110 static const struct file_operations proc_fdinfo_file_operations = { 111 .open = seq_fdinfo_open, 112 .read = seq_read, 113 .llseek = seq_lseek, 114 .release = single_release, 115 }; 116 117 static bool tid_fd_mode(struct task_struct *task, unsigned fd, fmode_t *mode) 118 { 119 struct file *file; 120 121 rcu_read_lock(); 122 file = task_lookup_fd_rcu(task, fd); 123 if (file) 124 *mode = file->f_mode; 125 rcu_read_unlock(); 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_fd_rcu(p, &fd); 269 ctx->pos = fd + 2LL; 270 if (!f) 271 break; 272 data.mode = f->f_mode; 273 rcu_read_unlock(); 274 data.fd = fd; 275 276 len = snprintf(name, sizeof(name), "%u", fd); 277 if (!proc_fill_cache(file, ctx, 278 name, len, instantiate, p, 279 &data)) 280 goto out; 281 cond_resched(); 282 rcu_read_lock(); 283 } 284 rcu_read_unlock(); 285 out: 286 put_task_struct(p); 287 return 0; 288 } 289 290 static int proc_readfd_count(struct inode *inode, loff_t *count) 291 { 292 struct task_struct *p = get_proc_task(inode); 293 struct fdtable *fdt; 294 295 if (!p) 296 return -ENOENT; 297 298 task_lock(p); 299 if (p->files) { 300 rcu_read_lock(); 301 302 fdt = files_fdtable(p->files); 303 *count = bitmap_weight(fdt->open_fds, fdt->max_fds); 304 305 rcu_read_unlock(); 306 } 307 task_unlock(p); 308 309 put_task_struct(p); 310 311 return 0; 312 } 313 314 static int proc_readfd(struct file *file, struct dir_context *ctx) 315 { 316 return proc_readfd_common(file, ctx, proc_fd_instantiate); 317 } 318 319 const struct file_operations proc_fd_operations = { 320 .read = generic_read_dir, 321 .iterate_shared = proc_readfd, 322 .llseek = generic_file_llseek, 323 }; 324 325 static struct dentry *proc_lookupfd(struct inode *dir, struct dentry *dentry, 326 unsigned int flags) 327 { 328 return proc_lookupfd_common(dir, dentry, proc_fd_instantiate); 329 } 330 331 /* 332 * /proc/pid/fd needs a special permission handler so that a process can still 333 * access /proc/self/fd after it has executed a setuid(). 334 */ 335 int proc_fd_permission(struct mnt_idmap *idmap, 336 struct inode *inode, int mask) 337 { 338 struct task_struct *p; 339 int rv; 340 341 rv = generic_permission(&nop_mnt_idmap, inode, mask); 342 if (rv == 0) 343 return rv; 344 345 rcu_read_lock(); 346 p = pid_task(proc_pid(inode), PIDTYPE_PID); 347 if (p && same_thread_group(p, current)) 348 rv = 0; 349 rcu_read_unlock(); 350 351 return rv; 352 } 353 354 static int proc_fd_getattr(struct mnt_idmap *idmap, 355 const struct path *path, struct kstat *stat, 356 u32 request_mask, unsigned int query_flags) 357 { 358 struct inode *inode = d_inode(path->dentry); 359 int rv = 0; 360 361 generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat); 362 363 /* If it's a directory, put the number of open fds there */ 364 if (S_ISDIR(inode->i_mode)) { 365 rv = proc_readfd_count(inode, &stat->size); 366 if (rv < 0) 367 return rv; 368 } 369 370 return rv; 371 } 372 373 const struct inode_operations proc_fd_inode_operations = { 374 .lookup = proc_lookupfd, 375 .permission = proc_fd_permission, 376 .getattr = proc_fd_getattr, 377 .setattr = proc_setattr, 378 }; 379 380 static struct dentry *proc_fdinfo_instantiate(struct dentry *dentry, 381 struct task_struct *task, const void *ptr) 382 { 383 const struct fd_data *data = ptr; 384 struct proc_inode *ei; 385 struct inode *inode; 386 387 inode = proc_pid_make_inode(dentry->d_sb, task, S_IFREG | S_IRUGO); 388 if (!inode) 389 return ERR_PTR(-ENOENT); 390 391 ei = PROC_I(inode); 392 ei->fd = data->fd; 393 394 inode->i_op = &proc_fdinfo_file_inode_operations; 395 396 inode->i_fop = &proc_fdinfo_file_operations; 397 tid_fd_update_inode(task, inode, 0); 398 399 d_set_d_op(dentry, &tid_fd_dentry_operations); 400 return d_splice_alias(inode, dentry); 401 } 402 403 static struct dentry * 404 proc_lookupfdinfo(struct inode *dir, struct dentry *dentry, unsigned int flags) 405 { 406 return proc_lookupfd_common(dir, dentry, proc_fdinfo_instantiate); 407 } 408 409 static int proc_readfdinfo(struct file *file, struct dir_context *ctx) 410 { 411 return proc_readfd_common(file, ctx, 412 proc_fdinfo_instantiate); 413 } 414 415 const struct inode_operations proc_fdinfo_inode_operations = { 416 .lookup = proc_lookupfdinfo, 417 .permission = proc_fdinfo_permission, 418 .setattr = proc_setattr, 419 }; 420 421 const struct file_operations proc_fdinfo_operations = { 422 .read = generic_read_dir, 423 .iterate_shared = proc_readfdinfo, 424 .llseek = generic_file_llseek, 425 }; 426