fs/proc/fd.c

   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/security.h>
  10 #include <linux/file.h>
  11 #include <linux/seq_file.h>
  12 #include <linux/fs.h>
  13
  14 #include <linux/proc_fs.h>
  15
  16 #include "../mount.h"
  17 #include "internal.h"
  18 #include "fd.h"
  19
  20 static int seq_show(struct seq_file *m, void *v)
  21 {
  22         struct files_struct *files = NULL;
  23         int f_flags = 0, ret = -ENOENT;
  24         struct file *file = NULL;
  25         struct task_struct *task;
  26
  27         task = get_proc_task(m->private);
  28         if (!task)
  29                 return -ENOENT;
  30
  31         files = get_files_struct(task);
  32         put_task_struct(task);
  33
  34         if (files) {
  35                 unsigned int fd = proc_fd(m->private);
  36
  37                 spin_lock(&files->file_lock);
  38                 file = fcheck_files(files, fd);
  39                 if (file) {
  40                         struct fdtable *fdt = files_fdtable(files);
  41
  42                         f_flags = file->f_flags;
  43                         if (close_on_exec(fd, fdt))
  44                                 f_flags |= O_CLOEXEC;
  45
  46                         get_file(file);
  47                         ret = 0;
  48                 }
  49                 spin_unlock(&files->file_lock);
  50                 put_files_struct(files);
  51         }
  52
  53         if (ret)
  54                 return ret;
  55
  56         seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\n",
  57                    (long long)file->f_pos, f_flags,
  58                    real_mount(file->f_path.mnt)->mnt_id);
  59
  60         show_fd_locks(m, file, files);
  61         if (seq_has_overflowed(m))
  62                 goto out;
  63
  64         if (file->f_op->show_fdinfo)
  65                 file->f_op->show_fdinfo(m, file);
  66
  67 out:
  68         fput(file);
  69         return 0;
  70 }
  71
  72 static int seq_fdinfo_open(struct inode *inode, struct file *file)
  73 {
  74         return single_open(file, seq_show, inode);
  75 }
  76
  77 static const struct file_operations proc_fdinfo_file_operations = {
  78         .open           = seq_fdinfo_open,
  79         .read           = seq_read,
  80         .llseek         = seq_lseek,
  81         .release        = single_release,
  82 };
  83
  84 static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags)
  85 {
  86         struct files_struct *files;
  87         struct task_struct *task;
  88         struct inode *inode;
  89         unsigned int fd;
  90
  91         if (flags & LOOKUP_RCU)
  92                 return -ECHILD;
  93
  94         inode = d_inode(dentry);
  95         task = get_proc_task(inode);
  96         fd = proc_fd(inode);
  97
  98         if (task) {
  99                 files = get_files_struct(task);
 100                 if (files) {
 101                         struct file *file;
 102
 103                         rcu_read_lock();
 104                         file = fcheck_files(files, fd);
 105                         if (file) {
 106                                 unsigned f_mode = file->f_mode;
 107
 108                                 rcu_read_unlock();
 109                                 put_files_struct(files);
 110
 111                                 task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);
 112
 113                                 if (S_ISLNK(inode->i_mode)) {
 114                                         unsigned i_mode = S_IFLNK;
 115                                         if (f_mode & FMODE_READ)
 116                                                 i_mode |= S_IRUSR | S_IXUSR;
 117                                         if (f_mode & FMODE_WRITE)
 118                                                 i_mode |= S_IWUSR | S_IXUSR;
 119                                         inode->i_mode = i_mode;
 120                                 }
 121
 122                                 security_task_to_inode(task, inode);
 123                                 put_task_struct(task);
 124                                 return 1;
 125                         }
 126                         rcu_read_unlock();
 127                         put_files_struct(files);
 128                 }
 129                 put_task_struct(task);
 130         }
 131         return 0;
 132 }
 133
 134 static const struct dentry_operations tid_fd_dentry_operations = {
 135         .d_revalidate   = tid_fd_revalidate,
 136         .d_delete       = pid_delete_dentry,
 137 };
 138
 139 static int proc_fd_link(struct dentry *dentry, struct path *path)
 140 {
 141         struct files_struct *files = NULL;
 142         struct task_struct *task;
 143         int ret = -ENOENT;
 144
 145         task = get_proc_task(d_inode(dentry));
 146         if (task) {
 147                 files = get_files_struct(task);
 148                 put_task_struct(task);
 149         }
 150
 151         if (files) {
 152                 unsigned int fd = proc_fd(d_inode(dentry));
 153                 struct file *fd_file;
 154
 155                 spin_lock(&files->file_lock);
 156                 fd_file = fcheck_files(files, fd);
 157                 if (fd_file) {
 158                         *path = fd_file->f_path;
 159                         path_get(&fd_file->f_path);
 160                         ret = 0;
 161                 }
 162                 spin_unlock(&files->file_lock);
 163                 put_files_struct(files);
 164         }
 165
 166         return ret;
 167 }
 168
 169 static int
 170 proc_fd_instantiate(struct inode *dir, struct dentry *dentry,
 171                     struct task_struct *task, const void *ptr)
 172 {
 173         unsigned fd = (unsigned long)ptr;
 174         struct proc_inode *ei;
 175         struct inode *inode;
 176
 177         inode = proc_pid_make_inode(dir->i_sb, task, S_IFLNK);
 178         if (!inode)
 179                 goto out;
 180
 181         ei = PROC_I(inode);
 182         ei->fd = fd;
 183
 184         inode->i_op = &proc_pid_link_inode_operations;
 185         inode->i_size = 64;
 186
 187         ei->op.proc_get_link = proc_fd_link;
 188
 189         d_set_d_op(dentry, &tid_fd_dentry_operations);
 190         d_add(dentry, inode);
 191
 192         /* Close the race of the process dying before we return the dentry */
 193         if (tid_fd_revalidate(dentry, 0))
 194                 return 0;
 195  out:
 196         return -ENOENT;
 197 }
 198
 199 static struct dentry *proc_lookupfd_common(struct inode *dir,
 200                                            struct dentry *dentry,
 201                                            instantiate_t instantiate)
 202 {
 203         struct task_struct *task = get_proc_task(dir);
 204         int result = -ENOENT;
 205         unsigned fd = name_to_int(&dentry->d_name);
 206
 207         if (!task)
 208                 goto out_no_task;
 209         if (fd == ~0U)
 210                 goto out;
 211
 212         result = instantiate(dir, dentry, task, (void *)(unsigned long)fd);
 213 out:
 214         put_task_struct(task);
 215 out_no_task:
 216         return ERR_PTR(result);
 217 }
 218
 219 static int proc_readfd_common(struct file *file, struct dir_context *ctx,
 220                               instantiate_t instantiate)
 221 {
 222         struct task_struct *p = get_proc_task(file_inode(file));
 223         struct files_struct *files;
 224         unsigned int fd;
 225
 226         if (!p)
 227                 return -ENOENT;
 228
 229         if (!dir_emit_dots(file, ctx))
 230                 goto out;
 231         files = get_files_struct(p);
 232         if (!files)
 233                 goto out;
 234
 235         rcu_read_lock();
 236         for (fd = ctx->pos - 2;
 237              fd < files_fdtable(files)->max_fds;
 238              fd++, ctx->pos++) {
 239                 char name[PROC_NUMBUF];
 240                 int len;
 241
 242                 if (!fcheck_files(files, fd))
 243                         continue;
 244                 rcu_read_unlock();
 245
 246                 len = snprintf(name, sizeof(name), "%u", fd);
 247                 if (!proc_fill_cache(file, ctx,
 248                                      name, len, instantiate, p,
 249                                      (void *)(unsigned long)fd))
 250                         goto out_fd_loop;
 251                 cond_resched();
 252                 rcu_read_lock();
 253         }
 254         rcu_read_unlock();
 255 out_fd_loop:
 256         put_files_struct(files);
 257 out:
 258         put_task_struct(p);
 259         return 0;
 260 }
 261
 262 static int proc_readfd(struct file *file, struct dir_context *ctx)
 263 {
 264         return proc_readfd_common(file, ctx, proc_fd_instantiate);
 265 }
 266
 267 const struct file_operations proc_fd_operations = {
 268         .read           = generic_read_dir,
 269         .iterate_shared = proc_readfd,
 270         .llseek         = generic_file_llseek,
 271 };
 272
 273 static struct dentry *proc_lookupfd(struct inode *dir, struct dentry *dentry,
 274                                     unsigned int flags)
 275 {
 276         return proc_lookupfd_common(dir, dentry, proc_fd_instantiate);
 277 }
 278
 279 /*
 280  * /proc/pid/fd needs a special permission handler so that a process can still
 281  * access /proc/self/fd after it has executed a setuid().
 282  */
 283 int proc_fd_permission(struct inode *inode, int mask)
 284 {
 285         struct task_struct *p;
 286         int rv;
 287
 288         rv = generic_permission(inode, mask);
 289         if (rv == 0)
 290                 return rv;
 291
 292         rcu_read_lock();
 293         p = pid_task(proc_pid(inode), PIDTYPE_PID);
 294         if (p && same_thread_group(p, current))
 295                 rv = 0;
 296         rcu_read_unlock();
 297
 298         return rv;
 299 }
 300
 301 const struct inode_operations proc_fd_inode_operations = {
 302         .lookup         = proc_lookupfd,
 303         .permission     = proc_fd_permission,
 304         .setattr        = proc_setattr,
 305 };
 306
 307 static int
 308 proc_fdinfo_instantiate(struct inode *dir, struct dentry *dentry,
 309                         struct task_struct *task, const void *ptr)
 310 {
 311         unsigned fd = (unsigned long)ptr;
 312         struct proc_inode *ei;
 313         struct inode *inode;
 314
 315         inode = proc_pid_make_inode(dir->i_sb, task, S_IFREG | S_IRUSR);
 316         if (!inode)
 317                 goto out;
 318
 319         ei = PROC_I(inode);
 320         ei->fd = fd;
 321
 322         inode->i_fop = &proc_fdinfo_file_operations;
 323
 324         d_set_d_op(dentry, &tid_fd_dentry_operations);
 325         d_add(dentry, inode);
 326
 327         /* Close the race of the process dying before we return the dentry */
 328         if (tid_fd_revalidate(dentry, 0))
 329                 return 0;
 330  out:
 331         return -ENOENT;
 332 }
 333
 334 static struct dentry *
 335 proc_lookupfdinfo(struct inode *dir, struct dentry *dentry, unsigned int flags)
 336 {
 337         return proc_lookupfd_common(dir, dentry, proc_fdinfo_instantiate);
 338 }
 339
 340 static int proc_readfdinfo(struct file *file, struct dir_context *ctx)
 341 {
 342         return proc_readfd_common(file, ctx,
 343                                   proc_fdinfo_instantiate);
 344 }
 345
 346 const struct inode_operations proc_fdinfo_inode_operations = {
 347         .lookup         = proc_lookupfdinfo,
 348         .setattr        = proc_setattr,
 349 };
 350
 351 const struct file_operations proc_fdinfo_operations = {
 352         .read           = generic_read_dir,
 353         .iterate_shared = proc_readfdinfo,
 354         .llseek         = generic_file_llseek,
 355 };