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%llu\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 dereferences 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_nochmod_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 file = fget_task(task, fd); 120 if (file) { 121 *mode = file->f_mode; 122 fput(file); 123 } 124 return !!file; 125 } 126 127 static void tid_fd_update_inode(struct task_struct *task, struct inode *inode, 128 fmode_t f_mode) 129 { 130 task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid); 131 132 if (S_ISLNK(inode->i_mode)) { 133 unsigned i_mode = S_IFLNK; 134 if (f_mode & FMODE_READ) 135 i_mode |= S_IRUSR | S_IXUSR; 136 if (f_mode & FMODE_WRITE) 137 i_mode |= S_IWUSR | S_IXUSR; 138 inode->i_mode = i_mode; 139 } 140 security_task_to_inode(task, inode); 141 } 142 143 static int tid_fd_revalidate(struct inode *dir, const struct qstr *name, 144 struct dentry *dentry, unsigned int flags) 145 { 146 struct task_struct *task; 147 struct inode *inode; 148 unsigned int fd; 149 150 if (flags & LOOKUP_RCU) 151 return -ECHILD; 152 153 inode = d_inode(dentry); 154 task = get_proc_task(inode); 155 fd = proc_fd(inode); 156 157 if (task) { 158 fmode_t f_mode; 159 if (tid_fd_mode(task, fd, &f_mode)) { 160 tid_fd_update_inode(task, inode, f_mode); 161 put_task_struct(task); 162 return 1; 163 } 164 put_task_struct(task); 165 } 166 return 0; 167 } 168 169 static const struct dentry_operations tid_fd_dentry_operations = { 170 .d_revalidate = tid_fd_revalidate, 171 .d_delete = pid_delete_dentry, 172 }; 173 174 static int proc_fd_link(struct dentry *dentry, struct path *path, 175 struct task_struct *task) 176 { 177 int ret = -ENOENT; 178 unsigned int fd = proc_fd(d_inode(dentry)); 179 struct file *fd_file; 180 181 fd_file = fget_task(task, fd); 182 if (fd_file) { 183 *path = fd_file->f_path; 184 path_get(&fd_file->f_path); 185 ret = 0; 186 fput(fd_file); 187 } 188 189 return ret; 190 } 191 192 struct fd_data { 193 fmode_t mode; 194 unsigned fd; 195 }; 196 197 static struct dentry *proc_fd_instantiate(struct dentry *dentry, 198 struct task_struct *task, const void *ptr) 199 { 200 const struct fd_data *data = ptr; 201 struct proc_inode *ei; 202 struct inode *inode; 203 204 inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK); 205 if (!inode) 206 return ERR_PTR(-ENOENT); 207 208 ei = PROC_I(inode); 209 ei->fd = data->fd; 210 211 inode->i_op = &proc_pid_link_inode_operations; 212 inode->i_size = 64; 213 214 ei->op.proc_get_link = proc_fd_link; 215 tid_fd_update_inode(task, inode, data->mode); 216 217 return proc_splice_unmountable(inode, dentry, 218 &tid_fd_dentry_operations); 219 } 220 221 static struct dentry *proc_lookupfd_common(struct inode *dir, 222 struct dentry *dentry, 223 instantiate_t instantiate) 224 { 225 struct task_struct *task = get_proc_task(dir); 226 struct fd_data data = {.fd = name_to_int(&dentry->d_name)}; 227 struct dentry *result = ERR_PTR(-ENOENT); 228 229 if (!task) 230 goto out_no_task; 231 if (data.fd == ~0U) 232 goto out; 233 if (!tid_fd_mode(task, data.fd, &data.mode)) 234 goto out; 235 236 result = instantiate(dentry, task, &data); 237 out: 238 put_task_struct(task); 239 out_no_task: 240 return result; 241 } 242 243 static int proc_readfd_common(struct file *file, struct dir_context *ctx, 244 instantiate_t instantiate) 245 { 246 struct task_struct *p = get_proc_task(file_inode(file)); 247 unsigned int fd; 248 249 if (!p) 250 return -ENOENT; 251 252 if (!dir_emit_dots(file, ctx)) 253 goto out; 254 255 for (fd = ctx->pos - 2;; fd++) { 256 struct file *f; 257 struct fd_data data; 258 char name[10 + 1]; 259 unsigned int len; 260 261 f = fget_task_next(p, &fd); 262 ctx->pos = fd + 2LL; 263 if (!f) 264 break; 265 data.mode = f->f_mode; 266 fput(f); 267 data.fd = fd; 268 269 len = snprintf(name, sizeof(name), "%u", fd); 270 if (!proc_fill_cache(file, ctx, 271 name, len, instantiate, p, 272 &data)) 273 break; 274 cond_resched(); 275 } 276 out: 277 put_task_struct(p); 278 return 0; 279 } 280 281 static int proc_readfd_count(struct inode *inode, loff_t *count) 282 { 283 struct task_struct *p = get_proc_task(inode); 284 struct fdtable *fdt; 285 286 if (!p) 287 return -ENOENT; 288 289 task_lock(p); 290 if (p->files) { 291 rcu_read_lock(); 292 293 fdt = files_fdtable(p->files); 294 *count = bitmap_weight(fdt->open_fds, fdt->max_fds); 295 296 rcu_read_unlock(); 297 } 298 task_unlock(p); 299 300 put_task_struct(p); 301 302 return 0; 303 } 304 305 static int proc_fd_iterate(struct file *file, struct dir_context *ctx) 306 { 307 return proc_readfd_common(file, ctx, proc_fd_instantiate); 308 } 309 310 const struct file_operations proc_fd_operations = { 311 .read = generic_read_dir, 312 .iterate_shared = proc_fd_iterate, 313 .llseek = generic_file_llseek, 314 }; 315 316 static struct dentry *proc_lookupfd(struct inode *dir, struct dentry *dentry, 317 unsigned int flags) 318 { 319 return proc_lookupfd_common(dir, dentry, proc_fd_instantiate); 320 } 321 322 /* 323 * /proc/pid/fd needs a special permission handler so that a process can still 324 * access /proc/self/fd after it has executed a setuid(). 325 */ 326 int proc_fd_permission(struct mnt_idmap *idmap, 327 struct inode *inode, int mask) 328 { 329 struct task_struct *p; 330 int rv; 331 332 rv = generic_permission(&nop_mnt_idmap, inode, mask); 333 if (rv == 0) 334 return rv; 335 336 rcu_read_lock(); 337 p = pid_task(proc_pid(inode), PIDTYPE_PID); 338 if (p && same_thread_group(p, current)) 339 rv = 0; 340 rcu_read_unlock(); 341 342 return rv; 343 } 344 345 static int proc_fd_getattr(struct mnt_idmap *idmap, 346 const struct path *path, struct kstat *stat, 347 u32 request_mask, unsigned int query_flags) 348 { 349 struct inode *inode = d_inode(path->dentry); 350 351 generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat); 352 return proc_readfd_count(inode, &stat->size); 353 } 354 355 const struct inode_operations proc_fd_inode_operations = { 356 .lookup = proc_lookupfd, 357 .permission = proc_fd_permission, 358 .getattr = proc_fd_getattr, 359 .setattr = proc_nochmod_setattr, 360 }; 361 362 static struct dentry *proc_fdinfo_instantiate(struct dentry *dentry, 363 struct task_struct *task, const void *ptr) 364 { 365 const struct fd_data *data = ptr; 366 struct proc_inode *ei; 367 struct inode *inode; 368 369 inode = proc_pid_make_inode(dentry->d_sb, task, S_IFREG | S_IRUGO); 370 if (!inode) 371 return ERR_PTR(-ENOENT); 372 373 ei = PROC_I(inode); 374 ei->fd = data->fd; 375 376 inode->i_op = &proc_fdinfo_file_inode_operations; 377 378 inode->i_fop = &proc_fdinfo_file_operations; 379 tid_fd_update_inode(task, inode, 0); 380 381 return proc_splice_unmountable(inode, dentry, 382 &tid_fd_dentry_operations); 383 } 384 385 static struct dentry * 386 proc_lookupfdinfo(struct inode *dir, struct dentry *dentry, unsigned int flags) 387 { 388 return proc_lookupfd_common(dir, dentry, proc_fdinfo_instantiate); 389 } 390 391 static int proc_fdinfo_iterate(struct file *file, struct dir_context *ctx) 392 { 393 return proc_readfd_common(file, ctx, 394 proc_fdinfo_instantiate); 395 } 396 397 const struct inode_operations proc_fdinfo_inode_operations = { 398 .lookup = proc_lookupfdinfo, 399 .permission = proc_fdinfo_permission, 400 .setattr = proc_nochmod_setattr, 401 }; 402 403 const struct file_operations proc_fdinfo_operations = { 404 .read = generic_read_dir, 405 .iterate_shared = proc_fdinfo_iterate, 406 .llseek = generic_file_llseek, 407 }; 408