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