[PATCH v2 08/30] fuse: extract fuse_fill_super_common()

Vivek Goyal
2019-05-15T19:28:07Z

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 38a572ba650d..84f094e4ac36 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -56,6 +56,25 @@ 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;
@@ -989,6 +1008,20 @@ 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 f02291469518..baf2966a753a 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);
@@ -482,7 +467,7 @@ 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;
@@ -559,12 +544,13 @@ 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)
{
@@ -1079,15 +1065,13 @@ 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;

@@ -1097,13 +1081,10 @@ 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 {
@@ -1120,19 +1101,6 @@ 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.
@@ -1143,7 +1111,7 @@ 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;
@@ -1163,17 +1131,17 @@ 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)
@@ -1181,20 +1149,15 @@ 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);
@@ -1203,23 +1166,12 @@ 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:
@@ -1227,11 +1179,62 @@ 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