fuse: ioctl: translate ENOSYS in outarg

Fuse shouldn't return ENOSYS from its ioctl implementation. If userspace
responds with ENOSYS it should be translated to ENOTTY.

There are two ways to return an error from the IOCTL request:

- fuse_out_header.error
- fuse_ioctl_out.result

Commit 02c0cab8e734 ("fuse: ioctl: translate ENOSYS") already fixed this
issue for the first case, but missed the second case. This patch fixes the
second case.

Reported-by: Jonathan Katz <jkatz@eitmlabs.org>
Closes: https://lore.kernel.org/all/CALKgVmcC1VUV_gJVq70n--omMJZUb4HSh_FqvLTHgNBc+HCLFQ@mail.gmail.com/
Fixes: 02c0cab8e734 ("fuse: ioctl: translate ENOSYS")
Cc: <stable@vger.kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fuse: add inode/permission checks to fileattr_get/fileattr_set

It looks like these checks were accidentally lost during the conversion to
fileattr API.

Fixes: 72227eac177d ("fuse: convert to fileattr")
Cc: <stable@vger.kernel.org> # v5.13
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs: port ->fileattr_set() to pass mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

use less confusing names for iov_iter direction initializers

READ/WRITE proved to be actively confusing - the meanings are
"data destination, as used with read(2)" and "data source, as
used with write(2)", but people keep interpreting those as
"we read data from it" and "we write data to it", i.e. exactly
the wrong way.

Call them ITER_DEST and ITER_SOURCE - at least that is harder
to misinterpret...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

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: 72db82115d2b ("ovl: copy up sync/noatime fileattr flags")
Fixes: 59efec7b9039 ("fuse: implement ioctl support")
Cc: <stable@vger.kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

x86: Remove toolchain check for X32 ABI capability

Commit 0bf6276392e9 ("x32: Warn and disable rather than error if
binutils too old") added a small test in arch/x86/Makefile because
binutils 2.22 or newer is needed to properly support elf32-x86-64. This
check is no longer necessary, as the minimum supported version of
binutils is 2.23, which is enforced at configuration time with
scripts/min-tool-version.sh.

Remove this check and replace all uses of CONFIG_X86_X32 with
CONFIG_X86_X32_ABI, as two symbols are no longer necessary.

[nathan: Rebase, fix up a few places where CONFIG_X86_X32 was still
used, and simplify commit message to satisfy -tip requirements]

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220314194842.3452-2-nathan@kernel.org

fuse: fix fileattr op failure

The fileattr API conversion broke lsattr on ntfs3g.

Previously the ioctl(... FS_IOC_GETFLAGS) returned an EINVAL error, but
after the conversion the error returned by the fuse filesystem was not
propagated back to the ioctl() system call, resulting in success being
returned with bogus values.

Fix by checking for outarg.result in fuse_priv_ioctl(), just as generic
ioctl code does.

Reported-by: Jean-Pierre André <jean-pierre.andre@wanadoo.fr>
Fixes: 72227eac177d ("fuse: convert to fileattr")
Cc: <stable@vger.kernel.org> # v5.13
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fuse: use kmap_local_page()

Due to the introduction of kmap_local_*, the storage of slots used for
short-term mapping has changed from per-CPU to per-thread. kmap_atomic()
disable preemption, while kmap_local_*() only disable migration.

There is no need to disable preemption in several kamp_atomic places used
in fuse.

Link: https://lwn.net/Articles/836144/
Signed-off-by: Peng Hao <flyingpeng@tencent.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fuse: convert to fileattr

Since fuse just passes ioctl args through to/from server, converting to the
fileattr API is more involved, than most other filesystems.

Both .fileattr_set() and .fileattr_get() need to obtain an open file to
operate on. The simplest way is with the following sequence:

FUSE_OPEN
FUSE_IOCTL
FUSE_RELEASE

If this turns out to be a performance problem, it could be optimized for
the case when there's already a file (any file) open for the inode.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fuse: move ioctl to separate source file

Next patch will expand ioctl code and fuse/file.c is large enough as it is.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>