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Commit 04d21a24 authored by Ilya Dryomov's avatar Ilya Dryomov
Browse files

Btrfs: rework error handling in btrfs_mount() 



Commits 6c41761f and 45ea6095 introduced the possibility of NULL pointer
dereference on error paths, also we would leave all devices busy and
leak fs_info with all sub-structures on error when trying to mount an
already mounted fs to a different directory.

Fix this by doing all allocations before trying to open any of the
devices, adjust error path for mount-already-mounted-fs case.

Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent 586e46e2

fs/btrfs/super.c

+21 −21
Original line number Diff line number Diff line
@@ -891,7 +891,6 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags, 
	struct super_block *s;

	struct dentry *root;

	struct btrfs_fs_devices *fs_devices = NULL;

	struct btrfs_root *tree_root = NULL;

	struct btrfs_fs_info *fs_info = NULL;

	fmode_t mode = FMODE_READ;

	char *subvol_name = NULL;
@@ -920,15 +919,6 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags, 
	if (error)

		return ERR_PTR(error);



	error = btrfs_open_devices(fs_devices, mode, fs_type);

	if (error)

		return ERR_PTR(error);



	if (!(flags & MS_RDONLY) && fs_devices->rw_devices == 0) {

		error = -EACCES;

		goto error_close_devices;

	}



	/*

	 * Setup a dummy root and fs_info for test/set super.  This is because

	 * we don't actually fill this stuff out until open_ctree, but we need
@@ -936,28 +926,36 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags, 
	 * then open_ctree will properly initialize everything later.

	 */

	fs_info = kzalloc(sizeof(struct btrfs_fs_info), GFP_NOFS);

	if (!fs_info) {

		error = -ENOMEM;

		goto error_close_devices;

	}

	tree_root = kzalloc(sizeof(struct btrfs_root), GFP_NOFS);

	if (!tree_root) {

	if (!fs_info)

		return ERR_PTR(-ENOMEM);



	fs_info->tree_root = kzalloc(sizeof(struct btrfs_root), GFP_NOFS);

	if (!fs_info->tree_root) {

		error = -ENOMEM;

		goto error_close_devices;

		goto error_fs_info;

	}

	fs_info->tree_root = tree_root;

	fs_info->tree_root->fs_info = fs_info;

	fs_info->fs_devices = fs_devices;

	tree_root->fs_info = fs_info;



	fs_info->super_copy = kzalloc(BTRFS_SUPER_INFO_SIZE, GFP_NOFS);

	fs_info->super_for_commit = kzalloc(BTRFS_SUPER_INFO_SIZE, GFP_NOFS);

	if (!fs_info->super_copy || !fs_info->super_for_commit) {

		error = -ENOMEM;

		goto error_fs_info;

	}



	error = btrfs_open_devices(fs_devices, mode, fs_type);

	if (error)

		goto error_fs_info;



	if (!(flags & MS_RDONLY) && fs_devices->rw_devices == 0) {

		error = -EACCES;

		goto error_close_devices;

	}



	bdev = fs_devices->latest_bdev;

	s = sget(fs_type, btrfs_test_super, btrfs_set_super, tree_root);

	s = sget(fs_type, btrfs_test_super, btrfs_set_super,

		 fs_info->tree_root);

	if (IS_ERR(s)) {

		error = PTR_ERR(s);

		goto error_close_devices;
@@ -966,7 +964,8 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags, 
	if (s->s_root) {

		if ((flags ^ s->s_flags) & MS_RDONLY) {

			deactivate_locked_super(s);

			return ERR_PTR(-EBUSY);

			error = -EBUSY;

			goto error_close_devices;

		}



		btrfs_close_devices(fs_devices);
@@ -997,6 +996,7 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags, 


error_close_devices:

	btrfs_close_devices(fs_devices);

error_fs_info:

	free_fs_info(fs_info);

	return ERR_PTR(error);

}