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    Subject[PATCH 08/13] fuse: extract fuse_fill_super_common()
    Date
    From: Stefan Hajnoczi <stefanha@redhat.com>

    fuse_fill_super() includes code to process the fd= option and link the
    struct fuse_dev to the fd's struct file. In virtio-fs there is no file
    descriptor because /dev/fuse is not used.

    This patch extracts fuse_fill_super_common() so that both classic fuse
    and virtio-fs can share the code to initialize a mount.

    parse_fuse_opt() is also extracted so that the fuse_fill_super_common()
    caller has access to the mount options. This allows classic fuse to
    handle the fd= option outside fuse_fill_super_common().

    Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
    Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
    ---
    fs/fuse/fuse_i.h | 33 ++++++++++++
    fs/fuse/inode.c | 137 ++++++++++++++++++++++++-----------------------
    2 files changed, 103 insertions(+), 67 deletions(-)

    diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
    index d4b27f048d81..062f929348cc 100644
    --- a/fs/fuse/fuse_i.h
    +++ b/fs/fuse/fuse_i.h
    @@ -60,6 +60,25 @@ extern struct mutex fuse_mutex;
    extern unsigned max_user_bgreq;
    extern unsigned max_user_congthresh;

    +/** Mount options */
    +struct fuse_mount_data {
    + int fd;
    + unsigned rootmode;
    + kuid_t user_id;
    + kgid_t group_id;
    + unsigned fd_present:1;
    + unsigned rootmode_present:1;
    + unsigned user_id_present:1;
    + unsigned group_id_present:1;
    + unsigned default_permissions:1;
    + unsigned allow_other:1;
    + unsigned max_read;
    + unsigned blksize;
    +
    + /* fuse_dev pointer to fill in, should contain NULL on entry */
    + void **fudptr;
    +};
    +
    /* One forget request */
    struct fuse_forget_link {
    struct fuse_forget_one forget_one;
    @@ -999,6 +1018,20 @@ struct fuse_dev *fuse_dev_alloc(struct fuse_conn *fc);
    void fuse_dev_free(struct fuse_dev *fud);
    void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req);

    +/**
    + * Parse a mount options string
    + */
    +int parse_fuse_opt(char *opt, struct fuse_mount_data *d, int is_bdev,
    + struct user_namespace *user_ns);
    +
    +/**
    + * Fill in superblock and initialize fuse connection
    + * @sb: partially-initialized superblock to fill in
    + * @mount_data: mount parameters
    + */
    +int fuse_fill_super_common(struct super_block *sb,
    + struct fuse_mount_data *mount_data);
    +
    /**
    * Add connection to control filesystem
    */
    diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
    index 14a4e915294c..9f21a0cb58b9 100644
    --- a/fs/fuse/inode.c
    +++ b/fs/fuse/inode.c
    @@ -59,21 +59,6 @@ MODULE_PARM_DESC(max_user_congthresh,
    /** Congestion starts at 75% of maximum */
    #define FUSE_DEFAULT_CONGESTION_THRESHOLD (FUSE_DEFAULT_MAX_BACKGROUND * 3 / 4)

    -struct fuse_mount_data {
    - int fd;
    - unsigned rootmode;
    - kuid_t user_id;
    - kgid_t group_id;
    - unsigned fd_present:1;
    - unsigned rootmode_present:1;
    - unsigned user_id_present:1;
    - unsigned group_id_present:1;
    - unsigned default_permissions:1;
    - unsigned allow_other:1;
    - unsigned max_read;
    - unsigned blksize;
    -};
    -
    struct fuse_forget_link *fuse_alloc_forget(void)
    {
    return kzalloc(sizeof(struct fuse_forget_link), GFP_KERNEL);
    @@ -477,7 +462,7 @@ static int fuse_match_uint(substring_t *s, unsigned int *res)
    return err;
    }

    -static int parse_fuse_opt(char *opt, struct fuse_mount_data *d, int is_bdev,
    +int parse_fuse_opt(char *opt, struct fuse_mount_data *d, int is_bdev,
    struct user_namespace *user_ns)
    {
    char *p;
    @@ -554,12 +539,13 @@ static int parse_fuse_opt(char *opt, struct fuse_mount_data *d, int is_bdev,
    }
    }

    - if (!d->fd_present || !d->rootmode_present ||
    - !d->user_id_present || !d->group_id_present)
    + if (!d->rootmode_present || !d->user_id_present ||
    + !d->group_id_present)
    return 0;

    return 1;
    }
    +EXPORT_SYMBOL_GPL(parse_fuse_opt);

    static int fuse_show_options(struct seq_file *m, struct dentry *root)
    {
    @@ -1076,15 +1062,13 @@ void fuse_dev_free(struct fuse_dev *fud)
    }
    EXPORT_SYMBOL_GPL(fuse_dev_free);

    -static int fuse_fill_super(struct super_block *sb, void *data, int silent)
    +int fuse_fill_super_common(struct super_block *sb,
    + struct fuse_mount_data *mount_data)
    {
    struct fuse_dev *fud;
    struct fuse_conn *fc;
    struct inode *root;
    - struct fuse_mount_data d;
    - struct file *file;
    struct dentry *root_dentry;
    - struct fuse_req *init_req;
    int err;
    int is_bdev = sb->s_bdev != NULL;

    @@ -1094,13 +1078,10 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)

    sb->s_flags &= ~(SB_NOSEC | SB_I_VERSION);

    - if (!parse_fuse_opt(data, &d, is_bdev, sb->s_user_ns))
    - goto err;
    -
    if (is_bdev) {
    #ifdef CONFIG_BLOCK
    err = -EINVAL;
    - if (!sb_set_blocksize(sb, d.blksize))
    + if (!sb_set_blocksize(sb, mount_data->blksize))
    goto err;
    #endif
    } else {
    @@ -1117,19 +1098,6 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
    if (sb->s_user_ns != &init_user_ns)
    sb->s_iflags |= SB_I_UNTRUSTED_MOUNTER;

    - file = fget(d.fd);
    - err = -EINVAL;
    - if (!file)
    - goto err;
    -
    - /*
    - * Require mount to happen from the same user namespace which
    - * opened /dev/fuse to prevent potential attacks.
    - */
    - if (file->f_op != &fuse_dev_operations ||
    - file->f_cred->user_ns != sb->s_user_ns)
    - goto err_fput;
    -
    /*
    * If we are not in the initial user namespace posix
    * acls must be translated.
    @@ -1140,7 +1108,7 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
    fc = kmalloc(sizeof(*fc), GFP_KERNEL);
    err = -ENOMEM;
    if (!fc)
    - goto err_fput;
    + goto err;

    fuse_conn_init(fc, sb->s_user_ns);
    fc->release = fuse_free_conn;
    @@ -1160,17 +1128,17 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
    fc->dont_mask = 1;
    sb->s_flags |= SB_POSIXACL;

    - fc->default_permissions = d.default_permissions;
    - fc->allow_other = d.allow_other;
    - fc->user_id = d.user_id;
    - fc->group_id = d.group_id;
    - fc->max_read = max_t(unsigned, 4096, d.max_read);
    + fc->default_permissions = mount_data->default_permissions;
    + fc->allow_other = mount_data->allow_other;
    + fc->user_id = mount_data->user_id;
    + fc->group_id = mount_data->group_id;
    + fc->max_read = max_t(unsigned, 4096, mount_data->max_read);

    /* Used by get_root_inode() */
    sb->s_fs_info = fc;

    err = -ENOMEM;
    - root = fuse_get_root_inode(sb, d.rootmode);
    + root = fuse_get_root_inode(sb, mount_data->rootmode);
    sb->s_d_op = &fuse_root_dentry_operations;
    root_dentry = d_make_root(root);
    if (!root_dentry)
    @@ -1178,20 +1146,15 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
    /* Root dentry doesn't have .d_revalidate */
    sb->s_d_op = &fuse_dentry_operations;

    - init_req = fuse_request_alloc(0);
    - if (!init_req)
    - goto err_put_root;
    - __set_bit(FR_BACKGROUND, &init_req->flags);
    -
    if (is_bdev) {
    fc->destroy_req = fuse_request_alloc(0);
    if (!fc->destroy_req)
    - goto err_free_init_req;
    + goto err_put_root;
    }

    mutex_lock(&fuse_mutex);
    err = -EINVAL;
    - if (file->private_data)
    + if (*mount_data->fudptr)
    goto err_unlock;

    err = fuse_ctl_add_conn(fc);
    @@ -1200,23 +1163,12 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)

    list_add_tail(&fc->entry, &fuse_conn_list);
    sb->s_root = root_dentry;
    - file->private_data = fud;
    + *mount_data->fudptr = fud;
    mutex_unlock(&fuse_mutex);
    - /*
    - * atomic_dec_and_test() in fput() provides the necessary
    - * memory barrier for file->private_data to be visible on all
    - * CPUs after this
    - */
    - fput(file);
    -
    - fuse_send_init(fc, init_req);
    -
    return 0;

    err_unlock:
    mutex_unlock(&fuse_mutex);
    - err_free_init_req:
    - fuse_request_free(init_req);
    err_put_root:
    dput(root_dentry);
    err_dev_free:
    @@ -1224,11 +1176,62 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
    err_put_conn:
    fuse_conn_put(fc);
    sb->s_fs_info = NULL;
    - err_fput:
    - fput(file);
    err:
    return err;
    }
    +EXPORT_SYMBOL_GPL(fuse_fill_super_common);
    +
    +static int fuse_fill_super(struct super_block *sb, void *data, int silent)
    +{
    + struct fuse_mount_data d;
    + struct file *file;
    + int is_bdev = sb->s_bdev != NULL;
    + int err;
    + struct fuse_req *init_req;
    +
    + err = -EINVAL;
    + if (!parse_fuse_opt(data, &d, is_bdev, sb->s_user_ns))
    + goto err;
    + if (!d.fd_present)
    + goto err;
    +
    + file = fget(d.fd);
    + if (!file)
    + goto err;
    +
    + /*
    + * Require mount to happen from the same user namespace which
    + * opened /dev/fuse to prevent potential attacks.
    + */
    + if ((file->f_op != &fuse_dev_operations) ||
    + (file->f_cred->user_ns != sb->s_user_ns))
    + goto err_fput;
    +
    + init_req = fuse_request_alloc(0);
    + if (!init_req)
    + goto err_fput;
    + __set_bit(FR_BACKGROUND, &init_req->flags);
    +
    + d.fudptr = &file->private_data;
    + err = fuse_fill_super_common(sb, &d);
    + if (err < 0)
    + goto err_free_init_req;
    + /*
    + * atomic_dec_and_test() in fput() provides the necessary
    + * memory barrier for file->private_data to be visible on all
    + * CPUs after this
    + */
    + fput(file);
    + fuse_send_init(get_fuse_conn_super(sb), init_req);
    + return 0;
    +
    +err_free_init_req:
    + fuse_request_free(init_req);
    +err_fput:
    + fput(file);
    +err:
    + return err;
    +}

    static struct dentry *fuse_mount(struct file_system_type *fs_type,
    int flags, const char *dev_name,
    --
    2.20.1
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