fs/proc/fd.c

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