linux/fs/proc/fd.c
<<
>>
Prefs
   1// SPDX-License-Identifier: GPL-2.0
   2#include <linux/sched/signal.h>
   3#include <linux/errno.h>
   4#include <linux/dcache.h>
   5#include <linux/path.h>
   6#include <linux/fdtable.h>
   7#include <linux/namei.h>
   8#include <linux/pid.h>
   9#include <linux/security.h>
  10#include <linux/file.h>
  11#include <linux/seq_file.h>
  12#include <linux/fs.h>
  13
  14#include <linux/proc_fs.h>
  15
  16#include "../mount.h"
  17#include "internal.h"
  18#include "fd.h"
  19
  20static int seq_show(struct seq_file *m, void *v)
  21{
  22        struct files_struct *files = NULL;
  23        int f_flags = 0, ret = -ENOENT;
  24        struct file *file = NULL;
  25        struct task_struct *task;
  26
  27        task = get_proc_task(m->private);
  28        if (!task)
  29                return -ENOENT;
  30
  31        task_lock(task);
  32        files = task->files;
  33        if (files) {
  34                unsigned int fd = proc_fd(m->private);
  35
  36                spin_lock(&files->file_lock);
  37                file = files_lookup_fd_locked(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        }
  50        task_unlock(task);
  51        put_task_struct(task);
  52
  53        if (ret)
  54                return ret;
  55
  56        seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\n",
  57                   (long long)file->f_pos, f_flags,
  58                   real_mount(file->f_path.mnt)->mnt_id);
  59
  60        /* show_fd_locks() never deferences files so a stale value is safe */
  61        show_fd_locks(m, file, files);
  62        if (seq_has_overflowed(m))
  63                goto out;
  64
  65        if (file->f_op->show_fdinfo)
  66                file->f_op->show_fdinfo(m, file);
  67
  68out:
  69        fput(file);
  70        return 0;
  71}
  72
  73static int seq_fdinfo_open(struct inode *inode, struct file *file)
  74{
  75        return single_open(file, seq_show, inode);
  76}
  77
  78static const struct file_operations proc_fdinfo_file_operations = {
  79        .open           = seq_fdinfo_open,
  80        .read           = seq_read,
  81        .llseek         = seq_lseek,
  82        .release        = single_release,
  83};
  84
  85static bool tid_fd_mode(struct task_struct *task, unsigned fd, fmode_t *mode)
  86{
  87        struct file *file;
  88
  89        rcu_read_lock();
  90        file = task_lookup_fd_rcu(task, fd);
  91        if (file)
  92                *mode = file->f_mode;
  93        rcu_read_unlock();
  94        return !!file;
  95}
  96
  97static void tid_fd_update_inode(struct task_struct *task, struct inode *inode,
  98                                fmode_t f_mode)
  99{
 100        task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);
 101
 102        if (S_ISLNK(inode->i_mode)) {
 103                unsigned i_mode = S_IFLNK;
 104                if (f_mode & FMODE_READ)
 105                        i_mode |= S_IRUSR | S_IXUSR;
 106                if (f_mode & FMODE_WRITE)
 107                        i_mode |= S_IWUSR | S_IXUSR;
 108                inode->i_mode = i_mode;
 109        }
 110        security_task_to_inode(task, inode);
 111}
 112
 113static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags)
 114{
 115        struct task_struct *task;
 116        struct inode *inode;
 117        unsigned int fd;
 118
 119        if (flags & LOOKUP_RCU)
 120                return -ECHILD;
 121
 122        inode = d_inode(dentry);
 123        task = get_proc_task(inode);
 124        fd = proc_fd(inode);
 125
 126        if (task) {
 127                fmode_t f_mode;
 128                if (tid_fd_mode(task, fd, &f_mode)) {
 129                        tid_fd_update_inode(task, inode, f_mode);
 130                        put_task_struct(task);
 131                        return 1;
 132                }
 133                put_task_struct(task);
 134        }
 135        return 0;
 136}
 137
 138static const struct dentry_operations tid_fd_dentry_operations = {
 139        .d_revalidate   = tid_fd_revalidate,
 140        .d_delete       = pid_delete_dentry,
 141};
 142
 143static int proc_fd_link(struct dentry *dentry, struct path *path)
 144{
 145        struct task_struct *task;
 146        int ret = -ENOENT;
 147
 148        task = get_proc_task(d_inode(dentry));
 149        if (task) {
 150                unsigned int fd = proc_fd(d_inode(dentry));
 151                struct file *fd_file;
 152
 153                fd_file = fget_task(task, fd);
 154                if (fd_file) {
 155                        *path = fd_file->f_path;
 156                        path_get(&fd_file->f_path);
 157                        ret = 0;
 158                        fput(fd_file);
 159                }
 160                put_task_struct(task);
 161        }
 162
 163        return ret;
 164}
 165
 166struct fd_data {
 167        fmode_t mode;
 168        unsigned fd;
 169};
 170
 171static struct dentry *proc_fd_instantiate(struct dentry *dentry,
 172        struct task_struct *task, const void *ptr)
 173{
 174        const struct fd_data *data = ptr;
 175        struct proc_inode *ei;
 176        struct inode *inode;
 177
 178        inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK);
 179        if (!inode)
 180                return ERR_PTR(-ENOENT);
 181
 182        ei = PROC_I(inode);
 183        ei->fd = data->fd;
 184
 185        inode->i_op = &proc_pid_link_inode_operations;
 186        inode->i_size = 64;
 187
 188        ei->op.proc_get_link = proc_fd_link;
 189        tid_fd_update_inode(task, inode, data->mode);
 190
 191        d_set_d_op(dentry, &tid_fd_dentry_operations);
 192        return d_splice_alias(inode, dentry);
 193}
 194
 195static struct dentry *proc_lookupfd_common(struct inode *dir,
 196                                           struct dentry *dentry,
 197                                           instantiate_t instantiate)
 198{
 199        struct task_struct *task = get_proc_task(dir);
 200        struct fd_data data = {.fd = name_to_int(&dentry->d_name)};
 201        struct dentry *result = ERR_PTR(-ENOENT);
 202
 203        if (!task)
 204                goto out_no_task;
 205        if (data.fd == ~0U)
 206                goto out;
 207        if (!tid_fd_mode(task, data.fd, &data.mode))
 208                goto out;
 209
 210        result = instantiate(dentry, task, &data);
 211out:
 212        put_task_struct(task);
 213out_no_task:
 214        return result;
 215}
 216
 217static int proc_readfd_common(struct file *file, struct dir_context *ctx,
 218                              instantiate_t instantiate)
 219{
 220        struct task_struct *p = get_proc_task(file_inode(file));
 221        unsigned int fd;
 222
 223        if (!p)
 224                return -ENOENT;
 225
 226        if (!dir_emit_dots(file, ctx))
 227                goto out;
 228
 229        rcu_read_lock();
 230        for (fd = ctx->pos - 2;; fd++) {
 231                struct file *f;
 232                struct fd_data data;
 233                char name[10 + 1];
 234                unsigned int len;
 235
 236                f = task_lookup_next_fd_rcu(p, &fd);
 237                ctx->pos = fd + 2LL;
 238                if (!f)
 239                        break;
 240                data.mode = f->f_mode;
 241                rcu_read_unlock();
 242                data.fd = fd;
 243
 244                len = snprintf(name, sizeof(name), "%u", fd);
 245                if (!proc_fill_cache(file, ctx,
 246                                     name, len, instantiate, p,
 247                                     &data))
 248                        goto out;
 249                cond_resched();
 250                rcu_read_lock();
 251        }
 252        rcu_read_unlock();
 253out:
 254        put_task_struct(p);
 255        return 0;
 256}
 257
 258static int proc_readfd(struct file *file, struct dir_context *ctx)
 259{
 260        return proc_readfd_common(file, ctx, proc_fd_instantiate);
 261}
 262
 263const struct file_operations proc_fd_operations = {
 264        .read           = generic_read_dir,
 265        .iterate_shared = proc_readfd,
 266        .llseek         = generic_file_llseek,
 267};
 268
 269static struct dentry *proc_lookupfd(struct inode *dir, struct dentry *dentry,
 270                                    unsigned int flags)
 271{
 272        return proc_lookupfd_common(dir, dentry, proc_fd_instantiate);
 273}
 274
 275/*
 276 * /proc/pid/fd needs a special permission handler so that a process can still
 277 * access /proc/self/fd after it has executed a setuid().
 278 */
 279int proc_fd_permission(struct user_namespace *mnt_userns,
 280                       struct inode *inode, int mask)
 281{
 282        struct task_struct *p;
 283        int rv;
 284
 285        rv = generic_permission(&init_user_ns, inode, mask);
 286        if (rv == 0)
 287                return rv;
 288
 289        rcu_read_lock();
 290        p = pid_task(proc_pid(inode), PIDTYPE_PID);
 291        if (p && same_thread_group(p, current))
 292                rv = 0;
 293        rcu_read_unlock();
 294
 295        return rv;
 296}
 297
 298const struct inode_operations proc_fd_inode_operations = {
 299        .lookup         = proc_lookupfd,
 300        .permission     = proc_fd_permission,
 301        .setattr        = proc_setattr,
 302};
 303
 304static struct dentry *proc_fdinfo_instantiate(struct dentry *dentry,
 305        struct task_struct *task, const void *ptr)
 306{
 307        const struct fd_data *data = ptr;
 308        struct proc_inode *ei;
 309        struct inode *inode;
 310
 311        inode = proc_pid_make_inode(dentry->d_sb, task, S_IFREG | S_IRUSR);
 312        if (!inode)
 313                return ERR_PTR(-ENOENT);
 314
 315        ei = PROC_I(inode);
 316        ei->fd = data->fd;
 317
 318        inode->i_fop = &proc_fdinfo_file_operations;
 319        tid_fd_update_inode(task, inode, 0);
 320
 321        d_set_d_op(dentry, &tid_fd_dentry_operations);
 322        return d_splice_alias(inode, dentry);
 323}
 324
 325static struct dentry *
 326proc_lookupfdinfo(struct inode *dir, struct dentry *dentry, unsigned int flags)
 327{
 328        return proc_lookupfd_common(dir, dentry, proc_fdinfo_instantiate);
 329}
 330
 331static int proc_readfdinfo(struct file *file, struct dir_context *ctx)
 332{
 333        return proc_readfd_common(file, ctx,
 334                                  proc_fdinfo_instantiate);
 335}
 336
 337const struct inode_operations proc_fdinfo_inode_operations = {
 338        .lookup         = proc_lookupfdinfo,
 339        .setattr        = proc_setattr,
 340};
 341
 342const struct file_operations proc_fdinfo_operations = {
 343        .read           = generic_read_dir,
 344        .iterate_shared = proc_readfdinfo,
 345        .llseek         = generic_file_llseek,
 346};
 347