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 #include <linux/fs.h>
  12
  13 #include <linux/proc_fs.h>
  14
  15 #include "../mount.h"
  16 #include "internal.h"
  17 #include "fd.h"
  18
  19 static int seq_show(struct seq_file *m, void *v)
  20 {
  21         struct files_struct *files = NULL;
  22         int f_flags = 0, ret = -ENOENT;
  23         struct file *file = NULL;
  24         struct task_struct *task;
  25
  26         task = get_proc_task(m->private);
  27         if (!task)
  28                 return -ENOENT;
  29
  30         files = get_files_struct(task);
  31         put_task_struct(task);
  32
  33         if (files) {
  34                 unsigned int fd = proc_fd(m->private);
  35
  36                 spin_lock(&files->file_lock);
  37                 file = fcheck_files(files, fd);
  38                 if (file) {
  39                         struct fdtable *fdt = files_fdtable(files);
  40
  41                         f_flags = file->f_flags;
  42                         if (close_on_exec(fd, fdt))
  43                                 f_flags |= O_CLOEXEC;
  44
  45                         get_file(file);
  46                         ret = 0;
  47                 }
  48                 spin_unlock(&files->file_lock);
  49                 put_files_struct(files);
  50         }
  51
  52         if (ret)
  53                 return ret;
  54
  55         seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\n",
  56                    (long long)file->f_pos, f_flags,
  57                    real_mount(file->f_path.mnt)->mnt_id);
  58
  59         show_fd_locks(m, file, files);
  60         if (seq_has_overflowed(m))
  61                 goto out;
  62
  63         if (file->f_op->show_fdinfo)
  64                 file->f_op->show_fdinfo(m, file);
  65
  66 out:
  67         fput(file);
  68         return 0;
  69 }
  70
  71 static int seq_fdinfo_open(struct inode *inode, struct file *file)
  72 {
  73         return single_open(file, seq_show, inode);
  74 }
  75
  76 static const struct file_operations proc_fdinfo_file_operations = {
  77         .open           = seq_fdinfo_open,
  78         .read           = seq_read,
  79         .llseek         = seq_lseek,
  80         .release        = single_release,
  81 };
  82
  83 static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags)
  84 {
  85         struct files_struct *files;
  86         struct task_struct *task;
  87         const struct cred *cred;
  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                                 if (task_dumpable(task)) {
 112                                         rcu_read_lock();
 113                                         cred = __task_cred(task);
 114                                         inode->i_uid = cred->euid;
 115                                         inode->i_gid = cred->egid;
 116                                         rcu_read_unlock();
 117                                 } else {
 118                                         inode->i_uid = GLOBAL_ROOT_UID;
 119                                         inode->i_gid = GLOBAL_ROOT_GID;
 120                                 }
 121
 122                                 if (S_ISLNK(inode->i_mode)) {
 123                                         unsigned i_mode = S_IFLNK;
 124                                         if (f_mode & FMODE_READ)
 125                                                 i_mode |= S_IRUSR | S_IXUSR;
 126                                         if (f_mode & FMODE_WRITE)
 127                                                 i_mode |= S_IWUSR | S_IXUSR;
 128                                         inode->i_mode = i_mode;
 129                                 }
 130
 131                                 security_task_to_inode(task, inode);
 132                                 put_task_struct(task);
 133                                 return 1;
 134                         }
 135                         rcu_read_unlock();
 136                         put_files_struct(files);
 137                 }
 138                 put_task_struct(task);
 139         }
 140         return 0;
 141 }
 142
 143 static const struct dentry_operations tid_fd_dentry_operations = {
 144         .d_revalidate   = tid_fd_revalidate,
 145         .d_delete       = pid_delete_dentry,
 146 };
 147
 148 static int proc_fd_link(struct dentry *dentry, struct path *path)
 149 {
 150         struct files_struct *files = NULL;
 151         struct task_struct *task;
 152         int ret = -ENOENT;
 153
 154         task = get_proc_task(d_inode(dentry));
 155         if (task) {
 156                 files = get_files_struct(task);
 157                 put_task_struct(task);
 158         }
 159
 160         if (files) {
 161                 unsigned int fd = proc_fd(d_inode(dentry));
 162                 struct file *fd_file;
 163
 164                 spin_lock(&files->file_lock);
 165                 fd_file = fcheck_files(files, fd);
 166                 if (fd_file) {
 167                         *path = fd_file->f_path;
 168                         path_get(&fd_file->f_path);
 169                         ret = 0;
 170                 }
 171                 spin_unlock(&files->file_lock);
 172                 put_files_struct(files);
 173         }
 174
 175         return ret;
 176 }
 177
 178 static int
 179 proc_fd_instantiate(struct inode *dir, struct dentry *dentry,
 180                     struct task_struct *task, const void *ptr)
 181 {
 182         unsigned fd = (unsigned long)ptr;
 183         struct proc_inode *ei;
 184         struct inode *inode;
 185
 186         inode = proc_pid_make_inode(dir->i_sb, task);
 187         if (!inode)
 188                 goto out;
 189
 190         ei = PROC_I(inode);
 191         ei->fd = fd;
 192
 193         inode->i_mode = S_IFLNK;
 194         inode->i_op = &proc_pid_link_inode_operations;
 195         inode->i_size = 64;
 196
 197         ei->op.proc_get_link = proc_fd_link;
 198
 199         d_set_d_op(dentry, &tid_fd_dentry_operations);
 200         d_add(dentry, inode);
 201
 202         /* Close the race of the process dying before we return the dentry */
 203         if (tid_fd_revalidate(dentry, 0))
 204                 return 0;
 205  out:
 206         return -ENOENT;
 207 }
 208
 209 static struct dentry *proc_lookupfd_common(struct inode *dir,
 210                                            struct dentry *dentry,
 211                                            instantiate_t instantiate)
 212 {
 213         struct task_struct *task = get_proc_task(dir);
 214         int result = -ENOENT;
 215         unsigned fd = name_to_int(&dentry->d_name);
 216
 217         if (!task)
 218                 goto out_no_task;
 219         if (fd == ~0U)
 220                 goto out;
 221
 222         result = instantiate(dir, dentry, task, (void *)(unsigned long)fd);
 223 out:
 224         put_task_struct(task);
 225 out_no_task:
 226         return ERR_PTR(result);
 227 }
 228
 229 static int proc_readfd_common(struct file *file, struct dir_context *ctx,
 230                               instantiate_t instantiate)
 231 {
 232         struct task_struct *p = get_proc_task(file_inode(file));
 233         struct files_struct *files;
 234         unsigned int fd;
 235
 236         if (!p)
 237                 return -ENOENT;
 238
 239         if (!dir_emit_dots(file, ctx))
 240                 goto out;
 241         files = get_files_struct(p);
 242         if (!files)
 243                 goto out;
 244
 245         rcu_read_lock();
 246         for (fd = ctx->pos - 2;
 247              fd < files_fdtable(files)->max_fds;
 248              fd++, ctx->pos++) {
 249                 char name[PROC_NUMBUF];
 250                 int len;
 251
 252                 if (!fcheck_files(files, fd))
 253                         continue;
 254                 rcu_read_unlock();
 255
 256                 len = snprintf(name, sizeof(name), "%u", fd);
 257                 if (!proc_fill_cache(file, ctx,
 258                                      name, len, instantiate, p,
 259                                      (void *)(unsigned long)fd))
 260                         goto out_fd_loop;
 261                 cond_resched();
 262                 rcu_read_lock();
 263         }
 264         rcu_read_unlock();
 265 out_fd_loop:
 266         put_files_struct(files);
 267 out:
 268         put_task_struct(p);
 269         return 0;
 270 }
 271
 272 static int proc_readfd(struct file *file, struct dir_context *ctx)
 273 {
 274         return proc_readfd_common(file, ctx, proc_fd_instantiate);
 275 }
 276
 277 const struct file_operations proc_fd_operations = {
 278         .read           = generic_read_dir,
 279         .iterate_shared = proc_readfd,
 280         .llseek         = generic_file_llseek,
 281 };
 282
 283 static struct dentry *proc_lookupfd(struct inode *dir, struct dentry *dentry,
 284                                     unsigned int flags)
 285 {
 286         return proc_lookupfd_common(dir, dentry, proc_fd_instantiate);
 287 }
 288
 289 /*
 290  * /proc/pid/fd needs a special permission handler so that a process can still
 291  * access /proc/self/fd after it has executed a setuid().
 292  */
 293 int proc_fd_permission(struct inode *inode, int mask)
 294 {
 295         struct task_struct *p;
 296         int rv;
 297
 298         rv = generic_permission(inode, mask);
 299         if (rv == 0)
 300                 return rv;
 301
 302         rcu_read_lock();
 303         p = pid_task(proc_pid(inode), PIDTYPE_PID);
 304         if (p && same_thread_group(p, current))
 305                 rv = 0;
 306         rcu_read_unlock();
 307
 308         return rv;
 309 }
 310
 311 const struct inode_operations proc_fd_inode_operations = {
 312         .lookup         = proc_lookupfd,
 313         .permission     = proc_fd_permission,
 314         .setattr        = proc_setattr,
 315 };
 316
 317 static int
 318 proc_fdinfo_instantiate(struct inode *dir, struct dentry *dentry,
 319                         struct task_struct *task, const void *ptr)
 320 {
 321         unsigned fd = (unsigned long)ptr;
 322         struct proc_inode *ei;
 323         struct inode *inode;
 324
 325         inode = proc_pid_make_inode(dir->i_sb, task);
 326         if (!inode)
 327                 goto out;
 328
 329         ei = PROC_I(inode);
 330         ei->fd = fd;
 331
 332         inode->i_mode = S_IFREG | S_IRUSR;
 333         inode->i_fop = &proc_fdinfo_file_operations;
 334
 335         d_set_d_op(dentry, &tid_fd_dentry_operations);
 336         d_add(dentry, inode);
 337
 338         /* Close the race of the process dying before we return the dentry */
 339         if (tid_fd_revalidate(dentry, 0))
 340                 return 0;
 341  out:
 342         return -ENOENT;
 343 }
 344
 345 static struct dentry *
 346 proc_lookupfdinfo(struct inode *dir, struct dentry *dentry, unsigned int flags)
 347 {
 348         return proc_lookupfd_common(dir, dentry, proc_fdinfo_instantiate);
 349 }
 350
 351 static int proc_readfdinfo(struct file *file, struct dir_context *ctx)
 352 {
 353         return proc_readfd_common(file, ctx,
 354                                   proc_fdinfo_instantiate);
 355 }
 356
 357 const struct inode_operations proc_fdinfo_inode_operations = {
 358         .lookup         = proc_lookupfdinfo,
 359         .setattr        = proc_setattr,
 360 };
 361
 362 const struct file_operations proc_fdinfo_operations = {
 363         .read           = generic_read_dir,
 364         .iterate_shared = proc_readfdinfo,
 365         .llseek         = generic_file_llseek,
 366 };