// SPDX-License-Identifier: GPL-2.0
/*
* linux/fs/readdir.c
*
* Copyright (C) 1995 Linus Torvalds
*/
#include <linux/stddef.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/time.h>
#include <linux/mm.h>
#include <linux/errno.h>
#include <linux/stat.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/fsnotify.h>
#include <linux/dirent.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/unistd.h>
#include <linux/compat.h>
#include <linux/uaccess.h>
/*
* Some filesystems were never converted to '->iterate_shared()'
* and their directory iterators want the inode lock held for
* writing. This wrapper allows for converting from the shared
* semantics to the exclusive inode use.
*/
int wrap_directory_iterator(struct file *file,
struct dir_context *ctx,
int (*iter)(struct file *, struct dir_context *))
{
struct inode *inode = file_inode(file);
int ret;
/*
* We'd love to have an 'inode_upgrade_trylock()' operation,
* see the comment in mmap_upgrade_trylock() in mm/memory.c.
*
* But considering this is for "filesystems that never got
* converted", it really doesn't matter.
*
* Also note that since we have to return with the lock held
* for reading, we can't use the "killable()" locking here,
* since we do need to get the lock even if we're dying.
*
* We could do the write part killably and then get the read
* lock unconditionally if it mattered, but see above on why
* this does the very simplistic conversion.
*/
up_read(&inode->i_rwsem);
down_write(&inode->i_rwsem);
/*
* Since we dropped the inode lock, we should do the
* DEADDIR test again. See 'iterate_dir()' below.
*
* Note that we don't need to re-do the f_pos games,
* since the file must be locked wrt f_pos anyway.
*/
ret = -ENOENT;
if (!IS_DEADDIR(inode))
ret = iter(file, ctx);
downgrade_write(&inode->i_rwsem);
return ret;
}
EXPORT_SYMBOL(wrap_directory_iterator);
/*
* Note the "unsafe_put_user()" semantics: we goto a
* label for errors.
*/
#define unsafe_copy_dirent_name(_dst, _src, _len, label) do { \
char __user *dst = (_dst); \
const char *src = (_src); \
size_t len = (_len); \
unsafe_put_user(0, dst+len, label); \
unsafe_copy_to_user(dst, src, len, label); \
} while (0)
int iterate_dir(struct file *file, struct dir_context *ctx)
{
struct inode *inode = file_inode(file);
int res = -ENOTDIR;
if (!file->f_op->iterate_shared)
goto out;
res = security_file_permission(file, MAY_READ);
if (res)
goto out;
res = fsnotify_file_perm(file, MAY_READ);
if (res)
goto out;
res = down_read_killable(&inode->i_rwsem);
if (res)
goto out;
res = -ENOENT;
if (!IS_DEADDIR(inode)) {
ctx->pos = file->f_pos;
res = file->f_op->iterate_shared(file, ctx);
file->f_pos = ctx->pos;
fsnotify_access(file);
file_accessed(file);
}
inode_unlock_shared(inode);
out:
return res;
}
EXPORT_SYMBOL(iterate_dir);
/*
* POSIX says that a dirent name cannot contain NULL or a '/'.
*
* It's not 100% clear what we should really do in this case.
* The filesystem is clearly corrupted, but returning a hard
* error means that you now don't see any of the other names
* either, so that isn't a perfect alternative.
*
* And if you return an error, what error do you use? Several
* filesystems seem to have decided on EUCLEAN being the error
* code for EFSCORRUPTED, and that may be the error to use. Or
* just EIO, which is perhaps more obvious to users.
*
* In order to see the other file names in the directory, the
* caller might want to make this a "soft" error: skip the
* entry, and return the error at the end instead.
*
* Note that this should likely do a "memchr(name, 0, len)"
* check too, since that would be filesystem corruption as
* well. However, that case can't actually confuse user space,
* which has to do a strlen() on the name anyway to find the
* filename length, and the above "soft error" worry means
* that it's probably better left alone until we have that
* issue clarified.
*
* Note the PATH_MAX check - it's arbitrary but the real
* kernel limit on a possible path component, not NAME_MAX,
* which is the technical standard limit.
*/
static int verify_dirent_name(const char *name, int len)
{
if (len <= 0 || len >= PATH_MAX)
return -EIO;
if (memchr(name, '/', len))
return -EIO;
return 0;
}
/*
* Traditional linux readdir() handling..
*
* "count=1" is a special case, meaning that the buffer is one
* dirent-structure in size and that the code can't handle more
* anyway. Thus the special "fillonedir()" function for that
* case (the low-level handlers don't need to care about this).
*/
#ifdef __ARCH_WANT_OLD_READDIR
struct old_linux_dirent {
unsigned long d_ino;
unsigned long d_offset;
unsigned short d_namlen;
char d_name[];
};
struct readdir_callback {
struct dir_context ctx;
struct old_linux_dirent __user * dirent;
int result;
};
static bool fillonedir(struct dir_context *ctx, const char *name, int namlen,
loff_t offset, u64 ino, unsigned int d_type)
{
struct readdir_callback *buf =
container_of(ctx, struct readdir_callback, ctx);
struct old_linux_dirent __user * dirent;
unsigned long d_ino;
if (buf->result)
return false;
buf->result = verify_dirent_name(name, namlen);
if (buf->result)
return false;
d_ino = ino;
if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
buf->result = -EOVERFLOW;
return false;
}
buf->result++;
dirent = buf->dirent;
if (!user_write_access_begin(dirent,
(unsigned long)(dirent->d_name + namlen + 1) -
(unsigned long)dirent))
goto efault;
unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
unsafe_put_user(offset, &dirent->d_offset, efault_end);
unsafe_put_user(namlen, &dirent->d_namlen, efault_end);
unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
user_write_access_end();
return true;
efault_end:
user_write_access_end();
efault:
buf->result = -EFAULT;
return false;
}
SYSCALL_DEFINE3(old_readdir, unsigned int, fd,
struct old_linux_dirent __user *, dirent, unsigned int, count)
{
int error;
struct fd f = fdget_pos(fd);
struct readdir_callback buf = {
.ctx.actor = fillonedir,
.dirent = dirent
};
if (!fd_file(f))
return -EBADF;
error = iterate_dir(fd_file(f), &buf.ctx);
if (buf.result)
error = buf.result;
fdput_pos(f);
return error;
}
#endif /* __ARCH_WANT_OLD_READDIR */
/*
* New, all-improved, singing, dancing, iBCS2-compliant getdents()
* interface.
*/
struct linux_dirent {
unsigned long d_ino;
unsigned long d_off;
unsigned short d_reclen;
char d_name[];
};
struct getdents_callback {
struct dir_context ctx;
struct linux_dirent __user * current_dir;
int prev_reclen;
int count;
int error;
};
static bool filldir(struct dir_context *ctx, const char *name, int namlen,
loff_t offset, u64 ino, unsigned int d_type)
{
struct linux_dirent __user *dirent, *prev;
struct getdents_callback *buf =
container_of(ctx, struct getdents_callback, ctx);
unsigned long d_ino;
int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2,
sizeof(long));
int prev_reclen;
buf->error = verify_dirent_name(name, namlen);
if (unlikely(buf->error))
return false;
buf->error = -EINVAL; /* only used if we fail.. */
if (reclen > buf->count)
return false;
d_ino = ino;
if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
buf->error = -EOVERFLOW;
return false;
}
prev_reclen = buf->prev_reclen;
if (prev_reclen && signal_pending(current))
return false;
dirent = buf->current_dir;
prev = (void __user *) dirent - prev_reclen;
if (!user_write_access_begin(prev, reclen + prev_reclen))
goto efault;
/* This might be 'dirent->d_off', but if so it will get overwritten */
unsafe_put_user(offset, &prev->d_off, efault_end);
unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
unsafe_put_user(d_type, (char __user *) dirent + reclen - 1, efault_end);
unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
user_write_access_end();
buf->current_dir = (void __user *)dirent + reclen;
buf->prev_reclen = reclen;
buf->count -= reclen;
return true;
efault_end:
user_write_access_end();
efault:
buf->error = -EFAULT;
return false;
}
SYSCALL_DEFINE3(getdents, unsigned int, fd,
struct linux_dirent __user *, dirent, unsigned int, count)
{
struct fd f;
struct getdents_callback buf = {
.ctx.actor = filldir,
.count = count,
.current_dir = dirent
};
int error;
f = fdget_pos(fd);
if (!fd_file(f))
return -EBADF;
error = iterate_dir(fd_file(f), &buf.ctx);
if (error >= 0)
error = buf.error;
if (buf.prev_reclen) {
struct linux_dirent __user * lastdirent;
lastdirent = (void __user *)buf.current_dir - buf.prev_reclen;
if (put_user(buf.ctx.pos, &lastdirent->d_off))
error = -EFAULT;
else
error = count - buf.count;
}
fdput_pos(f);
return error;
}
struct getdents_callback64 {
struct dir_context ctx;
struct linux_dirent64 __user * current_dir;
int prev_reclen;
int count;
int error;
};
static bool filldir64(struct dir_context *ctx, const char *name, int namlen,
loff_t offset, u64 ino, unsigned int d_type)
{
struct linux_dirent64 __user *dirent, *prev;
struct getdents_callback64 *buf =
container_of(ctx, struct getdents_callback64, ctx);
int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
sizeof(u64));
int prev_reclen;
buf->error = verify_dirent_name(name, namlen);
if (unlikely(buf->error))
return false;
buf->error = -EINVAL; /* only used if we fail.. */
if (reclen > buf->count)
return false;
prev_reclen = buf->prev_reclen;
if (prev_reclen && signal_pending(current))
return false;
dirent = buf->current_dir;
prev = (void __user *)dirent - prev_reclen;
if (!user_write_access_begin(prev, reclen + prev_reclen))
goto efault;
/* This might be 'dirent->d_off', but if so it will get overwritten */
unsafe_put_user(offset, &prev->d_off, efault_end);
unsafe_put_user(ino, &dirent->d_ino, efault_end);
unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
unsafe_put_user(d_type, &dirent->d_type, efault_end);
unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
user_write_access_end();
buf->prev_reclen = reclen;
buf->current_dir = (void __user *)dirent + reclen;
buf->count -= reclen;
return true;
efault_end:
user_write_access_end();
efault:
buf->error = -EFAULT;
return false;
}
SYSCALL_DEFINE3(getdents64, unsigned int, fd,
struct linux_dirent64 __user *, dirent, unsigned int, count)
{
struct fd f;
struct getdents_callback64 buf = {
.ctx.actor = filldir64,
.count = count,
.current_dir = dirent
};
int error;
f = fdget_pos(fd);
if (!fd_file(f))
return -EBADF;
error = iterate_dir(fd_file(f), &buf.ctx);
if (error >= 0)
error = buf.error;
if (buf.prev_reclen) {
struct linux_dirent64 __user * lastdirent;
typeof(lastdirent->d_off) d_off = buf.ctx.pos;
lastdirent = (void __user *) buf.current_dir - buf.prev_reclen;
if (put_user(d_off, &lastdirent->d_off))
error = -EFAULT;
else
error = count - buf.count;
}
fdput_pos(f);
return error;
}
#ifdef CONFIG_COMPAT
struct compat_old_linux_dirent {
compat_ulong_t d_ino;
compat_ulong_t d_offset;
unsigned short d_namlen;
char d_name[];
};
struct compat_readdir_callback {
struct dir_context ctx;
struct compat_old_linux_dirent __user *dirent;
int result;
};
static bool compat_fillonedir(struct dir_context *ctx, const char *name,
int namlen, loff_t offset, u64 ino,
unsigned int d_type)
{
struct compat_readdir_callback *buf =
container_of(ctx, struct compat_readdir_callback, ctx);
struct compat_old_linux_dirent __user *dirent;
compat_ulong_t d_ino;
if (buf->result)
return false;
buf->result = verify_dirent_name(name, namlen);
if (buf->result)
return false;
d_ino = ino;
if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
buf->result = -EOVERFLOW;
return false;
}
buf->result++;
dirent = buf->dirent;
if (!user_write_access_begin(dirent,
(unsigned long)(dirent->d_name + namlen + 1) -
(unsigned long)dirent))
goto efault;
unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
unsafe_put_user(offset, &dirent->d_offset, efault_end);
unsafe_put_user(namlen, &dirent->d_namlen, efault_end);
unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
user_write_access_end();
return true;
efault_end:
user_write_access_end();
efault:
buf->result = -EFAULT;
return false;
}
COMPAT_SYSCALL_DEFINE3(old_readdir, unsigned int, fd,
struct compat_old_linux_dirent __user *, dirent, unsigned int, count)
{
int error;
struct fd f = fdget_pos(fd);
struct compat_readdir_callback buf = {
.ctx.actor = compat_fillonedir,
.dirent = dirent
};
if (!fd_file(f))
return -EBADF;
error = iterate_dir(fd_file(f), &buf.ctx);
if (buf.result)
error = buf.result;
fdput_pos(f);
return error;
}
struct compat_linux_dirent {
compat_ulong_t d_ino;
compat_ulong_t d_off;
unsigned short d_reclen;
char d_name[];
};
struct compat_getdents_callback {
struct dir_context ctx;
struct compat_linux_dirent __user *current_dir;
int prev_reclen;
int count;
int error;
};
static bool compat_filldir(struct dir_context *ctx, const char *name, int namlen,
loff_t offset, u64 ino, unsigned int d_type)
{
struct compat_linux_dirent __user *dirent, *prev;
struct compat_getdents_callback *buf =
container_of(ctx, struct compat_getdents_callback, ctx);
compat_ulong_t d_ino;
int reclen = ALIGN(offsetof(struct compat_linux_dirent, d_name) +
namlen + 2, sizeof(compat_long_t));
int prev_reclen;
buf->error = verify_dirent_name(name, namlen);
if (unlikely(buf->error))
return false;
buf->error = -EINVAL; /* only used if we fail.. */
if (reclen > buf->count)
return false;
d_ino = ino;
if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
buf->error = -EOVERFLOW;
return false;
}
prev_reclen = buf->prev_reclen;
if (prev_reclen && signal_pending(current))
return false;
dirent = buf->current_dir;
prev = (void __user *) dirent - prev_reclen;
if (!user_write_access_begin(prev, reclen + prev_reclen))
goto efault;
unsafe_put_user(offset, &prev->d_off, efault_end);
unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
unsafe_put_user(d_type, (char __user *) dirent + reclen - 1, efault_end);
unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
user_write_access_end();
buf->prev_reclen = reclen;
buf->current_dir = (void __user *)dirent + reclen;
buf->count -= reclen;
return true;
efault_end:
user_write_access_end();
efault:
buf->error = -EFAULT;
return false;
}
COMPAT_SYSCALL_DEFINE3(getdents, unsigned int, fd,
struct compat_linux_dirent __user *, dirent, unsigned int, count)
{
struct fd f;
struct compat_getdents_callback buf = {
.ctx.actor = compat_filldir,
.current_dir = dirent,
.count = count
};
int error;
f = fdget_pos(fd);
if (!fd_file(f))
return -EBADF;
error = iterate_dir(fd_file(f), &buf.ctx);
if (error >= 0)
error = buf.error;
if (buf.prev_reclen) {
struct compat_linux_dirent __user * lastdirent;
lastdirent = (void __user *)buf.current_dir - buf.prev_reclen;
if (put_user(buf.ctx.pos, &lastdirent->d_off))
error = -EFAULT;
else
error = count - buf.count;
}
fdput_pos(f);
return error;
}
#endif
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