fs/proc/fd.c

   1 #include <linux/sched/signal.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         struct inode *inode;
  88         unsigned int fd;
  89
  90         if (flags & LOOKUP_RCU)
  91                 return -ECHILD;
  92
  93         inode = d_inode(dentry);
  94         task = get_proc_task(inode);
  95         fd = proc_fd(inode);
  96
  97         if (task) {
  98                 files = get_files_struct(task);
  99                 if (files) {
 100                         struct file *file;
 101
 102                         rcu_read_lock();
 103                         file = fcheck_files(files, fd);
 104                         if (file) {
 105                                 unsigned f_mode = file->f_mode;
 106
 107                                 rcu_read_unlock();
 108                                 put_files_struct(files);
 109
 110                                 task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);
 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         return 0;
 131 }
 132
 133 static const struct dentry_operations tid_fd_dentry_operations = {
 134         .d_revalidate   = tid_fd_revalidate,
 135         .d_delete       = pid_delete_dentry,
 136 };
 137
 138 static int proc_fd_link(struct dentry *dentry, struct path *path)
 139 {
 140         struct files_struct *files = NULL;
 141         struct task_struct *task;
 142         int ret = -ENOENT;
 143
 144         task = get_proc_task(d_inode(dentry));
 145         if (task) {
 146                 files = get_files_struct(task);
 147                 put_task_struct(task);
 148         }
 149
 150         if (files) {
 151                 unsigned int fd = proc_fd(d_inode(dentry));
 152                 struct file *fd_file;
 153
 154                 spin_lock(&files->file_lock);
 155                 fd_file = fcheck_files(files, fd);
 156                 if (fd_file) {
 157                         *path = fd_file->f_path;
 158                         path_get(&fd_file->f_path);
 159                         ret = 0;
 160                 }
 161                 spin_unlock(&files->file_lock);
 162                 put_files_struct(files);
 163         }
 164
 165         return ret;
 166 }
 167
 168 static int
 169 proc_fd_instantiate(struct inode *dir, struct dentry *dentry,
 170                     struct task_struct *task, const void *ptr)
 171 {
 172         unsigned fd = (unsigned long)ptr;
 173         struct proc_inode *ei;
 174         struct inode *inode;
 175
 176         inode = proc_pid_make_inode(dir->i_sb, task, S_IFLNK);
 177         if (!inode)
 178                 goto out;
 179
 180         ei = PROC_I(inode);
 181         ei->fd = fd;
 182
 183         inode->i_op = &proc_pid_link_inode_operations;
 184         inode->i_size = 64;
 185
 186         ei->op.proc_get_link = proc_fd_link;
 187
 188         d_set_d_op(dentry, &tid_fd_dentry_operations);
 189         d_add(dentry, inode);
 190
 191         /* Close the race of the process dying before we return the dentry */
 192         if (tid_fd_revalidate(dentry, 0))
 193                 return 0;
 194  out:
 195         return -ENOENT;
 196 }
 197
 198 static struct dentry *proc_lookupfd_common(struct inode *dir,
 199                                            struct dentry *dentry,
 200                                            instantiate_t instantiate)
 201 {
 202         struct task_struct *task = get_proc_task(dir);
 203         int result = -ENOENT;
 204         unsigned fd = name_to_int(&dentry->d_name);
 205
 206         if (!task)
 207                 goto out_no_task;
 208         if (fd == ~0U)
 209                 goto out;
 210
 211         result = instantiate(dir, dentry, task, (void *)(unsigned long)fd);
 212 out:
 213         put_task_struct(task);
 214 out_no_task:
 215         return ERR_PTR(result);
 216 }
 217
 218 static int proc_readfd_common(struct file *file, struct dir_context *ctx,
 219                               instantiate_t instantiate)
 220 {
 221         struct task_struct *p = get_proc_task(file_inode(file));
 222         struct files_struct *files;
 223         unsigned int fd;
 224
 225         if (!p)
 226                 return -ENOENT;
 227
 228         if (!dir_emit_dots(file, ctx))
 229                 goto out;
 230         files = get_files_struct(p);
 231         if (!files)
 232                 goto out;
 233
 234         rcu_read_lock();
 235         for (fd = ctx->pos - 2;
 236              fd < files_fdtable(files)->max_fds;
 237              fd++, ctx->pos++) {
 238                 char name[PROC_NUMBUF];
 239                 int len;
 240
 241                 if (!fcheck_files(files, fd))
 242                         continue;
 243                 rcu_read_unlock();
 244
 245                 len = snprintf(name, sizeof(name), "%u", fd);
 246                 if (!proc_fill_cache(file, ctx,
 247                                      name, len, instantiate, p,
 248                                      (void *)(unsigned long)fd))
 249                         goto out_fd_loop;
 250                 cond_resched();
 251                 rcu_read_lock();
 252         }
 253         rcu_read_unlock();
 254 out_fd_loop:
 255         put_files_struct(files);
 256 out:
 257         put_task_struct(p);
 258         return 0;
 259 }
 260
 261 static int proc_readfd(struct file *file, struct dir_context *ctx)
 262 {
 263         return proc_readfd_common(file, ctx, proc_fd_instantiate);
 264 }
 265
 266 const struct file_operations proc_fd_operations = {
 267         .read           = generic_read_dir,
 268         .iterate_shared = proc_readfd,
 269         .llseek         = generic_file_llseek,
 270 };
 271
 272 static struct dentry *proc_lookupfd(struct inode *dir, struct dentry *dentry,
 273                                     unsigned int flags)
 274 {
 275         return proc_lookupfd_common(dir, dentry, proc_fd_instantiate);
 276 }
 277
 278 /*
 279  * /proc/pid/fd needs a special permission handler so that a process can still
 280  * access /proc/self/fd after it has executed a setuid().
 281  */
 282 int proc_fd_permission(struct inode *inode, int mask)
 283 {
 284         struct task_struct *p;
 285         int rv;
 286
 287         rv = generic_permission(inode, mask);
 288         if (rv == 0)
 289                 return rv;
 290
 291         rcu_read_lock();
 292         p = pid_task(proc_pid(inode), PIDTYPE_PID);
 293         if (p && same_thread_group(p, current))
 294                 rv = 0;
 295         rcu_read_unlock();
 296
 297         return rv;
 298 }
 299
 300 const struct inode_operations proc_fd_inode_operations = {
 301         .lookup         = proc_lookupfd,
 302         .permission     = proc_fd_permission,
 303         .setattr        = proc_setattr,
 304 };
 305
 306 static int
 307 proc_fdinfo_instantiate(struct inode *dir, struct dentry *dentry,
 308                         struct task_struct *task, const void *ptr)
 309 {
 310         unsigned fd = (unsigned long)ptr;
 311         struct proc_inode *ei;
 312         struct inode *inode;
 313
 314         inode = proc_pid_make_inode(dir->i_sb, task, S_IFREG | S_IRUSR);
 315         if (!inode)
 316                 goto out;
 317
 318         ei = PROC_I(inode);
 319         ei->fd = fd;
 320
 321         inode->i_fop = &proc_fdinfo_file_operations;
 322
 323         d_set_d_op(dentry, &tid_fd_dentry_operations);
 324         d_add(dentry, inode);
 325
 326         /* Close the race of the process dying before we return the dentry */
 327         if (tid_fd_revalidate(dentry, 0))
 328                 return 0;
 329  out:
 330         return -ENOENT;
 331 }
 332
 333 static struct dentry *
 334 proc_lookupfdinfo(struct inode *dir, struct dentry *dentry, unsigned int flags)
 335 {
 336         return proc_lookupfd_common(dir, dentry, proc_fdinfo_instantiate);
 337 }
 338
 339 static int proc_readfdinfo(struct file *file, struct dir_context *ctx)
 340 {
 341         return proc_readfd_common(file, ctx,
 342                                   proc_fdinfo_instantiate);
 343 }
 344
 345 const struct inode_operations proc_fdinfo_inode_operations = {
 346         .lookup         = proc_lookupfdinfo,
 347         .setattr        = proc_setattr,
 348 };
 349
 350 const struct file_operations proc_fdinfo_operations = {
 351         .read           = generic_read_dir,
 352         .iterate_shared = proc_readfdinfo,
 353         .llseek         = generic_file_llseek,
 354 };