linux/fs/fuse/ioctl.c
Miklos Szeredi 02c0cab8e7 fuse: ioctl: translate ENOSYS
Overlayfs may fail to complete updates when a filesystem lacks
fileattr/xattr syscall support and responds with an ENOSYS error code,
resulting in an unexpected "Function not implemented" error.

This bug may occur with FUSE filesystems, such as davfs2.

Steps to reproduce:

  # install davfs2, e.g., apk add davfs2
  mkdir /test mkdir /test/lower /test/upper /test/work /test/mnt
  yes '' | mount -t davfs -o ro http://some-web-dav-server/path \
    /test/lower
  mount -t overlay -o upperdir=/test/upper,lowerdir=/test/lower \
    -o workdir=/test/work overlay /test/mnt

  # when "some-file" exists in the lowerdir, this fails with "Function
  # not implemented", with dmesg showing "overlayfs: failed to retrieve
  # lower fileattr (/some-file, err=-38)"
  touch /test/mnt/some-file

The underlying cause of this regresion is actually in FUSE, which fails to
translate the ENOSYS error code returned by userspace filesystem (which
means that the ioctl operation is not supported) to ENOTTY.

Reported-by: Christian Kohlschütter <christian@kohlschutter.com>
Fixes: 72db82115d ("ovl: copy up sync/noatime fileattr flags")
Fixes: 59efec7b90 ("fuse: implement ioctl support")
Cc: <stable@vger.kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2022-07-21 16:06:18 +02:00

505 lines
13 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2017 Red Hat, Inc.
*/
#include "fuse_i.h"
#include <linux/uio.h>
#include <linux/compat.h>
#include <linux/fileattr.h>
static ssize_t fuse_send_ioctl(struct fuse_mount *fm, struct fuse_args *args)
{
ssize_t ret = fuse_simple_request(fm, args);
/* Translate ENOSYS, which shouldn't be returned from fs */
if (ret == -ENOSYS)
ret = -ENOTTY;
return ret;
}
/*
* CUSE servers compiled on 32bit broke on 64bit kernels because the
* ABI was defined to be 'struct iovec' which is different on 32bit
* and 64bit. Fortunately we can determine which structure the server
* used from the size of the reply.
*/
static int fuse_copy_ioctl_iovec_old(struct iovec *dst, void *src,
size_t transferred, unsigned count,
bool is_compat)
{
#ifdef CONFIG_COMPAT
if (count * sizeof(struct compat_iovec) == transferred) {
struct compat_iovec *ciov = src;
unsigned i;
/*
* With this interface a 32bit server cannot support
* non-compat (i.e. ones coming from 64bit apps) ioctl
* requests
*/
if (!is_compat)
return -EINVAL;
for (i = 0; i < count; i++) {
dst[i].iov_base = compat_ptr(ciov[i].iov_base);
dst[i].iov_len = ciov[i].iov_len;
}
return 0;
}
#endif
if (count * sizeof(struct iovec) != transferred)
return -EIO;
memcpy(dst, src, transferred);
return 0;
}
/* Make sure iov_length() won't overflow */
static int fuse_verify_ioctl_iov(struct fuse_conn *fc, struct iovec *iov,
size_t count)
{
size_t n;
u32 max = fc->max_pages << PAGE_SHIFT;
for (n = 0; n < count; n++, iov++) {
if (iov->iov_len > (size_t) max)
return -ENOMEM;
max -= iov->iov_len;
}
return 0;
}
static int fuse_copy_ioctl_iovec(struct fuse_conn *fc, struct iovec *dst,
void *src, size_t transferred, unsigned count,
bool is_compat)
{
unsigned i;
struct fuse_ioctl_iovec *fiov = src;
if (fc->minor < 16) {
return fuse_copy_ioctl_iovec_old(dst, src, transferred,
count, is_compat);
}
if (count * sizeof(struct fuse_ioctl_iovec) != transferred)
return -EIO;
for (i = 0; i < count; i++) {
/* Did the server supply an inappropriate value? */
if (fiov[i].base != (unsigned long) fiov[i].base ||
fiov[i].len != (unsigned long) fiov[i].len)
return -EIO;
dst[i].iov_base = (void __user *) (unsigned long) fiov[i].base;
dst[i].iov_len = (size_t) fiov[i].len;
#ifdef CONFIG_COMPAT
if (is_compat &&
(ptr_to_compat(dst[i].iov_base) != fiov[i].base ||
(compat_size_t) dst[i].iov_len != fiov[i].len))
return -EIO;
#endif
}
return 0;
}
/*
* For ioctls, there is no generic way to determine how much memory
* needs to be read and/or written. Furthermore, ioctls are allowed
* to dereference the passed pointer, so the parameter requires deep
* copying but FUSE has no idea whatsoever about what to copy in or
* out.
*
* This is solved by allowing FUSE server to retry ioctl with
* necessary in/out iovecs. Let's assume the ioctl implementation
* needs to read in the following structure.
*
* struct a {
* char *buf;
* size_t buflen;
* }
*
* On the first callout to FUSE server, inarg->in_size and
* inarg->out_size will be NULL; then, the server completes the ioctl
* with FUSE_IOCTL_RETRY set in out->flags, out->in_iovs set to 1 and
* the actual iov array to
*
* { { .iov_base = inarg.arg, .iov_len = sizeof(struct a) } }
*
* which tells FUSE to copy in the requested area and retry the ioctl.
* On the second round, the server has access to the structure and
* from that it can tell what to look for next, so on the invocation,
* it sets FUSE_IOCTL_RETRY, out->in_iovs to 2 and iov array to
*
* { { .iov_base = inarg.arg, .iov_len = sizeof(struct a) },
* { .iov_base = a.buf, .iov_len = a.buflen } }
*
* FUSE will copy both struct a and the pointed buffer from the
* process doing the ioctl and retry ioctl with both struct a and the
* buffer.
*
* This time, FUSE server has everything it needs and completes ioctl
* without FUSE_IOCTL_RETRY which finishes the ioctl call.
*
* Copying data out works the same way.
*
* Note that if FUSE_IOCTL_UNRESTRICTED is clear, the kernel
* automatically initializes in and out iovs by decoding @cmd with
* _IOC_* macros and the server is not allowed to request RETRY. This
* limits ioctl data transfers to well-formed ioctls and is the forced
* behavior for all FUSE servers.
*/
long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
unsigned int flags)
{
struct fuse_file *ff = file->private_data;
struct fuse_mount *fm = ff->fm;
struct fuse_ioctl_in inarg = {
.fh = ff->fh,
.cmd = cmd,
.arg = arg,
.flags = flags
};
struct fuse_ioctl_out outarg;
struct iovec *iov_page = NULL;
struct iovec *in_iov = NULL, *out_iov = NULL;
unsigned int in_iovs = 0, out_iovs = 0, max_pages;
size_t in_size, out_size, c;
ssize_t transferred;
int err, i;
struct iov_iter ii;
struct fuse_args_pages ap = {};
#if BITS_PER_LONG == 32
inarg.flags |= FUSE_IOCTL_32BIT;
#else
if (flags & FUSE_IOCTL_COMPAT) {
inarg.flags |= FUSE_IOCTL_32BIT;
#ifdef CONFIG_X86_X32_ABI
if (in_x32_syscall())
inarg.flags |= FUSE_IOCTL_COMPAT_X32;
#endif
}
#endif
/* assume all the iovs returned by client always fits in a page */
BUILD_BUG_ON(sizeof(struct fuse_ioctl_iovec) * FUSE_IOCTL_MAX_IOV > PAGE_SIZE);
err = -ENOMEM;
ap.pages = fuse_pages_alloc(fm->fc->max_pages, GFP_KERNEL, &ap.descs);
iov_page = (struct iovec *) __get_free_page(GFP_KERNEL);
if (!ap.pages || !iov_page)
goto out;
fuse_page_descs_length_init(ap.descs, 0, fm->fc->max_pages);
/*
* If restricted, initialize IO parameters as encoded in @cmd.
* RETRY from server is not allowed.
*/
if (!(flags & FUSE_IOCTL_UNRESTRICTED)) {
struct iovec *iov = iov_page;
iov->iov_base = (void __user *)arg;
iov->iov_len = _IOC_SIZE(cmd);
if (_IOC_DIR(cmd) & _IOC_WRITE) {
in_iov = iov;
in_iovs = 1;
}
if (_IOC_DIR(cmd) & _IOC_READ) {
out_iov = iov;
out_iovs = 1;
}
}
retry:
inarg.in_size = in_size = iov_length(in_iov, in_iovs);
inarg.out_size = out_size = iov_length(out_iov, out_iovs);
/*
* Out data can be used either for actual out data or iovs,
* make sure there always is at least one page.
*/
out_size = max_t(size_t, out_size, PAGE_SIZE);
max_pages = DIV_ROUND_UP(max(in_size, out_size), PAGE_SIZE);
/* make sure there are enough buffer pages and init request with them */
err = -ENOMEM;
if (max_pages > fm->fc->max_pages)
goto out;
while (ap.num_pages < max_pages) {
ap.pages[ap.num_pages] = alloc_page(GFP_KERNEL | __GFP_HIGHMEM);
if (!ap.pages[ap.num_pages])
goto out;
ap.num_pages++;
}
/* okay, let's send it to the client */
ap.args.opcode = FUSE_IOCTL;
ap.args.nodeid = ff->nodeid;
ap.args.in_numargs = 1;
ap.args.in_args[0].size = sizeof(inarg);
ap.args.in_args[0].value = &inarg;
if (in_size) {
ap.args.in_numargs++;
ap.args.in_args[1].size = in_size;
ap.args.in_pages = true;
err = -EFAULT;
iov_iter_init(&ii, WRITE, in_iov, in_iovs, in_size);
for (i = 0; iov_iter_count(&ii) && !WARN_ON(i >= ap.num_pages); i++) {
c = copy_page_from_iter(ap.pages[i], 0, PAGE_SIZE, &ii);
if (c != PAGE_SIZE && iov_iter_count(&ii))
goto out;
}
}
ap.args.out_numargs = 2;
ap.args.out_args[0].size = sizeof(outarg);
ap.args.out_args[0].value = &outarg;
ap.args.out_args[1].size = out_size;
ap.args.out_pages = true;
ap.args.out_argvar = true;
transferred = fuse_send_ioctl(fm, &ap.args);
err = transferred;
if (transferred < 0)
goto out;
/* did it ask for retry? */
if (outarg.flags & FUSE_IOCTL_RETRY) {
void *vaddr;
/* no retry if in restricted mode */
err = -EIO;
if (!(flags & FUSE_IOCTL_UNRESTRICTED))
goto out;
in_iovs = outarg.in_iovs;
out_iovs = outarg.out_iovs;
/*
* Make sure things are in boundary, separate checks
* are to protect against overflow.
*/
err = -ENOMEM;
if (in_iovs > FUSE_IOCTL_MAX_IOV ||
out_iovs > FUSE_IOCTL_MAX_IOV ||
in_iovs + out_iovs > FUSE_IOCTL_MAX_IOV)
goto out;
vaddr = kmap_local_page(ap.pages[0]);
err = fuse_copy_ioctl_iovec(fm->fc, iov_page, vaddr,
transferred, in_iovs + out_iovs,
(flags & FUSE_IOCTL_COMPAT) != 0);
kunmap_local(vaddr);
if (err)
goto out;
in_iov = iov_page;
out_iov = in_iov + in_iovs;
err = fuse_verify_ioctl_iov(fm->fc, in_iov, in_iovs);
if (err)
goto out;
err = fuse_verify_ioctl_iov(fm->fc, out_iov, out_iovs);
if (err)
goto out;
goto retry;
}
err = -EIO;
if (transferred > inarg.out_size)
goto out;
err = -EFAULT;
iov_iter_init(&ii, READ, out_iov, out_iovs, transferred);
for (i = 0; iov_iter_count(&ii) && !WARN_ON(i >= ap.num_pages); i++) {
c = copy_page_to_iter(ap.pages[i], 0, PAGE_SIZE, &ii);
if (c != PAGE_SIZE && iov_iter_count(&ii))
goto out;
}
err = 0;
out:
free_page((unsigned long) iov_page);
while (ap.num_pages)
__free_page(ap.pages[--ap.num_pages]);
kfree(ap.pages);
return err ? err : outarg.result;
}
EXPORT_SYMBOL_GPL(fuse_do_ioctl);
long fuse_ioctl_common(struct file *file, unsigned int cmd,
unsigned long arg, unsigned int flags)
{
struct inode *inode = file_inode(file);
struct fuse_conn *fc = get_fuse_conn(inode);
if (!fuse_allow_current_process(fc))
return -EACCES;
if (fuse_is_bad(inode))
return -EIO;
return fuse_do_ioctl(file, cmd, arg, flags);
}
long fuse_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
return fuse_ioctl_common(file, cmd, arg, 0);
}
long fuse_file_compat_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
return fuse_ioctl_common(file, cmd, arg, FUSE_IOCTL_COMPAT);
}
static int fuse_priv_ioctl(struct inode *inode, struct fuse_file *ff,
unsigned int cmd, void *ptr, size_t size)
{
struct fuse_mount *fm = ff->fm;
struct fuse_ioctl_in inarg;
struct fuse_ioctl_out outarg;
FUSE_ARGS(args);
int err;
memset(&inarg, 0, sizeof(inarg));
inarg.fh = ff->fh;
inarg.cmd = cmd;
#if BITS_PER_LONG == 32
inarg.flags |= FUSE_IOCTL_32BIT;
#endif
if (S_ISDIR(inode->i_mode))
inarg.flags |= FUSE_IOCTL_DIR;
if (_IOC_DIR(cmd) & _IOC_READ)
inarg.out_size = size;
if (_IOC_DIR(cmd) & _IOC_WRITE)
inarg.in_size = size;
args.opcode = FUSE_IOCTL;
args.nodeid = ff->nodeid;
args.in_numargs = 2;
args.in_args[0].size = sizeof(inarg);
args.in_args[0].value = &inarg;
args.in_args[1].size = inarg.in_size;
args.in_args[1].value = ptr;
args.out_numargs = 2;
args.out_args[0].size = sizeof(outarg);
args.out_args[0].value = &outarg;
args.out_args[1].size = inarg.out_size;
args.out_args[1].value = ptr;
err = fuse_send_ioctl(fm, &args);
if (!err) {
if (outarg.result < 0)
err = outarg.result;
else if (outarg.flags & FUSE_IOCTL_RETRY)
err = -EIO;
}
return err;
}
static struct fuse_file *fuse_priv_ioctl_prepare(struct inode *inode)
{
struct fuse_mount *fm = get_fuse_mount(inode);
bool isdir = S_ISDIR(inode->i_mode);
if (!S_ISREG(inode->i_mode) && !isdir)
return ERR_PTR(-ENOTTY);
return fuse_file_open(fm, get_node_id(inode), O_RDONLY, isdir);
}
static void fuse_priv_ioctl_cleanup(struct inode *inode, struct fuse_file *ff)
{
fuse_file_release(inode, ff, O_RDONLY, NULL, S_ISDIR(inode->i_mode));
}
int fuse_fileattr_get(struct dentry *dentry, struct fileattr *fa)
{
struct inode *inode = d_inode(dentry);
struct fuse_file *ff;
unsigned int flags;
struct fsxattr xfa;
int err;
ff = fuse_priv_ioctl_prepare(inode);
if (IS_ERR(ff))
return PTR_ERR(ff);
if (fa->flags_valid) {
err = fuse_priv_ioctl(inode, ff, FS_IOC_GETFLAGS,
&flags, sizeof(flags));
if (err)
goto cleanup;
fileattr_fill_flags(fa, flags);
} else {
err = fuse_priv_ioctl(inode, ff, FS_IOC_FSGETXATTR,
&xfa, sizeof(xfa));
if (err)
goto cleanup;
fileattr_fill_xflags(fa, xfa.fsx_xflags);
fa->fsx_extsize = xfa.fsx_extsize;
fa->fsx_nextents = xfa.fsx_nextents;
fa->fsx_projid = xfa.fsx_projid;
fa->fsx_cowextsize = xfa.fsx_cowextsize;
}
cleanup:
fuse_priv_ioctl_cleanup(inode, ff);
return err;
}
int fuse_fileattr_set(struct user_namespace *mnt_userns,
struct dentry *dentry, struct fileattr *fa)
{
struct inode *inode = d_inode(dentry);
struct fuse_file *ff;
unsigned int flags = fa->flags;
struct fsxattr xfa;
int err;
ff = fuse_priv_ioctl_prepare(inode);
if (IS_ERR(ff))
return PTR_ERR(ff);
if (fa->flags_valid) {
err = fuse_priv_ioctl(inode, ff, FS_IOC_SETFLAGS,
&flags, sizeof(flags));
if (err)
goto cleanup;
} else {
memset(&xfa, 0, sizeof(xfa));
xfa.fsx_xflags = fa->fsx_xflags;
xfa.fsx_extsize = fa->fsx_extsize;
xfa.fsx_nextents = fa->fsx_nextents;
xfa.fsx_projid = fa->fsx_projid;
xfa.fsx_cowextsize = fa->fsx_cowextsize;
err = fuse_priv_ioctl(inode, ff, FS_IOC_FSSETXATTR,
&xfa, sizeof(xfa));
}
cleanup:
fuse_priv_ioctl_cleanup(inode, ff);
return err;
}