On Fri 21-03-25 20:48:42, Andrey Albershteyn wrote:
> From: Andrey Albershteyn <aalbe...@redhat.com>
> 
> Introduce getfsxattrat and setfsxattrat syscalls to manipulate inode
> extended attributes/flags. The syscalls take parent directory fd and
> path to the child together with struct fsxattr.
> 
> This is an alternative to FS_IOC_FSSETXATTR ioctl with a difference
> that file don't need to be open as we can reference it with a path
> instead of fd. By having this we can manipulated inode extended
> attributes not only on regular files but also on special ones. This
> is not possible with FS_IOC_FSSETXATTR ioctl as with special files
> we can not call ioctl() directly on the filesystem inode using fd.
> 
> This patch adds two new syscalls which allows userspace to get/set
> extended inode attributes on special files by using parent directory
> and a path - *at() like syscall.
> 
> CC: linux-...@vger.kernel.org
> CC: linux-fsde...@vger.kernel.org
> CC: linux-...@vger.kernel.org
> Signed-off-by: Andrey Albershteyn <aalbe...@redhat.com>
> Acked-by: Arnd Bergmann <a...@arndb.de>

Looks good. Just two nits below:

> +SYSCALL_DEFINE5(getfsxattrat, int, dfd, const char __user *, filename,
> +             struct fsxattr __user *, ufsx, size_t, usize,
> +             unsigned int, at_flags)
> +{
> +     struct fileattr fa = {};
> +     struct path filepath;
> +     int error;
> +     unsigned int lookup_flags = 0;
> +     struct filename *name;
> +     struct fsxattr fsx = {};
> +
> +     BUILD_BUG_ON(sizeof(struct fsxattr) < FSXATTR_SIZE_VER0);
> +     BUILD_BUG_ON(sizeof(struct fsxattr) != FSXATTR_SIZE_LATEST);
> +
> +     if ((at_flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
> +             return -EINVAL;
> +
> +     if (!(at_flags & AT_SYMLINK_NOFOLLOW))
> +             lookup_flags |= LOOKUP_FOLLOW;
> +
> +     if (at_flags & AT_EMPTY_PATH)
> +             lookup_flags |= LOOKUP_EMPTY;

Strictly speaking setting LOOKUP_EMPTY does not have any effect because
empty names are already handled by getname_maybe_null(). But it does not
hurt either so I don't really care...

> +
> +     if (usize > PAGE_SIZE)
> +             return -E2BIG;
> +
> +     if (usize < FSXATTR_SIZE_VER0)
> +             return -EINVAL;
> +
> +     name = getname_maybe_null(filename, at_flags);
> +     if (!name) {
> +             CLASS(fd, f)(dfd);
> +
> +             if (fd_empty(f))
> +                     return -EBADF;
> +             error = vfs_fileattr_get(file_dentry(fd_file(f)), &fa);
> +     } else {
> +             error = filename_lookup(dfd, name, lookup_flags, &filepath,
> +                                     NULL);
> +             if (error)
> +                     goto out;
> +             error = vfs_fileattr_get(filepath.dentry, &fa);
> +             path_put(&filepath);
> +     }
> +     if (error == -ENOIOCTLCMD)
> +             error = -EOPNOTSUPP;
> +     if (!error) {
> +             fileattr_to_fsxattr(&fa, &fsx);
> +             error = copy_struct_to_user(ufsx, usize, &fsx,
> +                                         sizeof(struct fsxattr), NULL);
> +     }
> +out:
> +     putname(name);
> +     return error;
> +}
> +
> +SYSCALL_DEFINE5(setfsxattrat, int, dfd, const char __user *, filename,
> +             struct fsxattr __user *, ufsx, size_t, usize,
> +             unsigned int, at_flags)
> +{
> +     struct fileattr fa;
> +     struct path filepath;
> +     int error;
> +     unsigned int lookup_flags = 0;
> +     struct filename *name;
> +     struct mnt_idmap *idmap;
> +     struct dentry *dentry;
> +     struct vfsmount *mnt;
> +     struct fsxattr fsx = {};
> +
> +     BUILD_BUG_ON(sizeof(struct fsxattr) < FSXATTR_SIZE_VER0);
> +     BUILD_BUG_ON(sizeof(struct fsxattr) != FSXATTR_SIZE_LATEST);
> +
> +     if ((at_flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
> +             return -EINVAL;
> +
> +     if (!(at_flags & AT_SYMLINK_NOFOLLOW))
> +             lookup_flags |= LOOKUP_FOLLOW;
> +
> +     if (at_flags & AT_EMPTY_PATH)
> +             lookup_flags |= LOOKUP_EMPTY;

Same comment regarding LOOKUP_EMPTY here.

> +
> +     if (usize > PAGE_SIZE)
> +             return -E2BIG;
> +
> +     if (usize < FSXATTR_SIZE_VER0)
> +             return -EINVAL;
> +
> +     error = copy_struct_from_user(&fsx, sizeof(struct fsxattr), ufsx, 
> usize);
> +     if (error)
> +             return error;
> +
> +     fsxattr_to_fileattr(&fsx, &fa);
> +
> +     name = getname_maybe_null(filename, at_flags);
> +     if (!name) {
> +             CLASS(fd, f)(dfd);
> +
> +             if (fd_empty(f))
> +                     return -EBADF;
> +
> +             idmap = file_mnt_idmap(fd_file(f));
> +             dentry = file_dentry(fd_file(f));
> +             mnt = fd_file(f)->f_path.mnt;
> +     } else {
> +             error = filename_lookup(dfd, name, lookup_flags, &filepath,
> +                                     NULL);
> +             if (error)
> +                     return error;
> +
> +             idmap = mnt_idmap(filepath.mnt);
> +             dentry = filepath.dentry;
> +             mnt = filepath.mnt;
> +     }
> +
> +     error = mnt_want_write(mnt);
> +     if (!error) {
> +             error = vfs_fileattr_set(idmap, dentry, &fa);
> +             if (error == -ENOIOCTLCMD)
> +                     error = -EOPNOTSUPP;
> +             mnt_drop_write(mnt);
> +     }
> +
> +     path_put(&filepath);

filepath will not be initialized here in case of name == NULL. 

> +     return error;
> +}

With this fixed feel free to add:

Reviewed-by: Jan Kara <j...@suse.cz>

                                                                Honza

-- 
Jan Kara <j...@suse.com>
SUSE Labs, CR

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