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/ptrace.h>
  10#include <linux/security.h>
  11#include <linux/file.h>
  12#include <linux/seq_file.h>
  13#include <linux/fs.h>
  14
  15#include <linux/proc_fs.h>
  16
  17#include "../mount.h"
  18#include "internal.h"
  19#include "fd.h"
  20
  21static int seq_show(struct seq_file *m, void *v)
  22{
  23        struct files_struct *files = NULL;
  24        int f_flags = 0, ret = -ENOENT;
  25        struct file *file = NULL;
  26        struct task_struct *task;
  27
  28        task = get_proc_task(m->private);
  29        if (!task)
  30                return -ENOENT;
  31
  32        task_lock(task);
  33        files = task->files;
  34        if (files) {
  35                unsigned int fd = proc_fd(m->private);
  36
  37                spin_lock(&files->file_lock);
  38                file = files_lookup_fd_locked(files, fd);
  39                if (file) {
  40                        struct fdtable *fdt = files_fdtable(files);
  41
  42                        f_flags = file->f_flags;
  43                        if (close_on_exec(fd, fdt))
  44                                f_flags |= O_CLOEXEC;
  45
  46                        get_file(file);
  47                        ret = 0;
  48                }
  49                spin_unlock(&files->file_lock);
  50        }
  51        task_unlock(task);
  52        put_task_struct(task);
  53
  54        if (ret)
  55                return ret;
  56
  57        seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\nino:\t%lu\n",
  58                   (long long)file->f_pos, f_flags,
  59                   real_mount(file->f_path.mnt)->mnt_id,
  60                   file_inode(file)->i_ino);
  61
  62        /* show_fd_locks() never deferences files so a stale value is safe */
  63        show_fd_locks(m, file, files);
  64        if (seq_has_overflowed(m))
  65                goto out;
  66
  67        if (file->f_op->show_fdinfo)
  68                file->f_op->show_fdinfo(m, file);
  69
  70out:
  71        fput(file);
  72        return 0;
  73}
  74
  75static int seq_fdinfo_open(struct inode *inode, struct file *file)
  76{
  77        bool allowed = false;
  78        struct task_struct *task = get_proc_task(inode);
  79
  80        if (!task)
  81                return -ESRCH;
  82
  83        allowed = ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
  84        put_task_struct(task);
  85
  86        if (!allowed)
  87                return -EACCES;
  88
  89        return single_open(file, seq_show, inode);
  90}
  91
  92static const struct file_operations proc_fdinfo_file_operations = {
  93        .open           = seq_fdinfo_open,
  94        .read           = seq_read,
  95        .llseek         = seq_lseek,
  96        .release        = single_release,
  97};
  98
  99static bool tid_fd_mode(struct task_struct *task, unsigned fd, fmode_t *mode)
 100{
 101        struct file *file;
 102
 103        rcu_read_lock();
 104        file = task_lookup_fd_rcu(task, fd);
 105        if (file)
 106                *mode = file->f_mode;
 107        rcu_read_unlock();
 108        return !!file;
 109}
 110
 111static void tid_fd_update_inode(struct task_struct *task, struct inode *inode,
 112                                fmode_t f_mode)
 113{
 114        task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);
 115
 116        if (S_ISLNK(inode->i_mode)) {
 117                unsigned i_mode = S_IFLNK;
 118                if (f_mode & FMODE_READ)
 119                        i_mode |= S_IRUSR | S_IXUSR;
 120                if (f_mode & FMODE_WRITE)
 121                        i_mode |= S_IWUSR | S_IXUSR;
 122                inode->i_mode = i_mode;
 123        }
 124        security_task_to_inode(task, inode);
 125}
 126
 127static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags)
 128{
 129        struct task_struct *task;
 130        struct inode *inode;
 131        unsigned int fd;
 132
 133        if (flags & LOOKUP_RCU)
 134                return -ECHILD;
 135
 136        inode = d_inode(dentry);
 137        task = get_proc_task(inode);
 138        fd = proc_fd(inode);
 139
 140        if (task) {
 141                fmode_t f_mode;
 142                if (tid_fd_mode(task, fd, &f_mode)) {
 143                        tid_fd_update_inode(task, inode, f_mode);
 144                        put_task_struct(task);
 145                        return 1;
 146                }
 147                put_task_struct(task);
 148        }
 149        return 0;
 150}
 151
 152static const struct dentry_operations tid_fd_dentry_operations = {
 153        .d_revalidate   = tid_fd_revalidate,
 154        .d_delete       = pid_delete_dentry,
 155};
 156
 157static int proc_fd_link(struct dentry *dentry, struct path *path)
 158{
 159        struct task_struct *task;
 160        int ret = -ENOENT;
 161
 162        task = get_proc_task(d_inode(dentry));
 163        if (task) {
 164                unsigned int fd = proc_fd(d_inode(dentry));
 165                struct file *fd_file;
 166
 167                fd_file = fget_task(task, fd);
 168                if (fd_file) {
 169                        *path = fd_file->f_path;
 170                        path_get(&fd_file->f_path);
 171                        ret = 0;
 172                        fput(fd_file);
 173                }
 174                put_task_struct(task);
 175        }
 176
 177        return ret;
 178}
 179
 180struct fd_data {
 181        fmode_t mode;
 182        unsigned fd;
 183};
 184
 185static struct dentry *proc_fd_instantiate(struct dentry *dentry,
 186        struct task_struct *task, const void *ptr)
 187{
 188        const struct fd_data *data = ptr;
 189        struct proc_inode *ei;
 190        struct inode *inode;
 191
 192        inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK);
 193        if (!inode)
 194                return ERR_PTR(-ENOENT);
 195
 196        ei = PROC_I(inode);
 197        ei->fd = data->fd;
 198
 199        inode->i_op = &proc_pid_link_inode_operations;
 200        inode->i_size = 64;
 201
 202        ei->op.proc_get_link = proc_fd_link;
 203        tid_fd_update_inode(task, inode, data->mode);
 204
 205        d_set_d_op(dentry, &tid_fd_dentry_operations);
 206        return d_splice_alias(inode, dentry);
 207}
 208
 209static 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        struct fd_data data = {.fd = name_to_int(&dentry->d_name)};
 215        struct dentry *result = ERR_PTR(-ENOENT);
 216
 217        if (!task)
 218                goto out_no_task;
 219        if (data.fd == ~0U)
 220                goto out;
 221        if (!tid_fd_mode(task, data.fd, &data.mode))
 222                goto out;
 223
 224        result = instantiate(dentry, task, &data);
 225out:
 226        put_task_struct(task);
 227out_no_task:
 228        return result;
 229}
 230
 231static int proc_readfd_common(struct file *file, struct dir_context *ctx,
 232                              instantiate_t instantiate)
 233{
 234        struct task_struct *p = get_proc_task(file_inode(file));
 235        unsigned int fd;
 236
 237        if (!p)
 238                return -ENOENT;
 239
 240        if (!dir_emit_dots(file, ctx))
 241                goto out;
 242
 243        rcu_read_lock();
 244        for (fd = ctx->pos - 2;; fd++) {
 245                struct file *f;
 246                struct fd_data data;
 247                char name[10 + 1];
 248                unsigned int len;
 249
 250                f = task_lookup_next_fd_rcu(p, &fd);
 251                ctx->pos = fd + 2LL;
 252                if (!f)
 253                        break;
 254                data.mode = f->f_mode;
 255                rcu_read_unlock();
 256                data.fd = fd;
 257
 258                len = snprintf(name, sizeof(name), "%u", fd);
 259                if (!proc_fill_cache(file, ctx,
 260                                     name, len, instantiate, p,
 261                                     &data))
 262                        goto out;
 263                cond_resched();
 264                rcu_read_lock();
 265        }
 266        rcu_read_unlock();
 267out:
 268        put_task_struct(p);
 269        return 0;
 270}
 271
 272static int proc_readfd(struct file *file, struct dir_context *ctx)
 273{
 274        return proc_readfd_common(file, ctx, proc_fd_instantiate);
 275}
 276
 277const struct file_operations proc_fd_operations = {
 278        .read           = generic_read_dir,
 279        .iterate_shared = proc_readfd,
 280        .llseek         = generic_file_llseek,
 281};
 282
 283static 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 */
 293int proc_fd_permission(struct user_namespace *mnt_userns,
 294                       struct inode *inode, int mask)
 295{
 296        struct task_struct *p;
 297        int rv;
 298
 299        rv = generic_permission(&init_user_ns, inode, mask);
 300        if (rv == 0)
 301                return rv;
 302
 303        rcu_read_lock();
 304        p = pid_task(proc_pid(inode), PIDTYPE_PID);
 305        if (p && same_thread_group(p, current))
 306                rv = 0;
 307        rcu_read_unlock();
 308
 309        return rv;
 310}
 311
 312const struct inode_operations proc_fd_inode_operations = {
 313        .lookup         = proc_lookupfd,
 314        .permission     = proc_fd_permission,
 315        .setattr        = proc_setattr,
 316};
 317
 318static struct dentry *proc_fdinfo_instantiate(struct dentry *dentry,
 319        struct task_struct *task, const void *ptr)
 320{
 321        const struct fd_data *data = ptr;
 322        struct proc_inode *ei;
 323        struct inode *inode;
 324
 325        inode = proc_pid_make_inode(dentry->d_sb, task, S_IFREG | S_IRUGO);
 326        if (!inode)
 327                return ERR_PTR(-ENOENT);
 328
 329        ei = PROC_I(inode);
 330        ei->fd = data->fd;
 331
 332        inode->i_fop = &proc_fdinfo_file_operations;
 333        tid_fd_update_inode(task, inode, 0);
 334
 335        d_set_d_op(dentry, &tid_fd_dentry_operations);
 336        return d_splice_alias(inode, dentry);
 337}
 338
 339static struct dentry *
 340proc_lookupfdinfo(struct inode *dir, struct dentry *dentry, unsigned int flags)
 341{
 342        return proc_lookupfd_common(dir, dentry, proc_fdinfo_instantiate);
 343}
 344
 345static int proc_readfdinfo(struct file *file, struct dir_context *ctx)
 346{
 347        return proc_readfd_common(file, ctx,
 348                                  proc_fdinfo_instantiate);
 349}
 350
 351const struct inode_operations proc_fdinfo_inode_operations = {
 352        .lookup         = proc_lookupfdinfo,
 353        .setattr        = proc_setattr,
 354};
 355
 356const struct file_operations proc_fdinfo_operations = {
 357        .read           = generic_read_dir,
 358        .iterate_shared = proc_readfdinfo,
 359        .llseek         = generic_file_llseek,
 360};
 361
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.