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