| Date | Thu, 16 Feb 2023 15:21:21 +0530 | Subject | Re: [PATCH v10 1/9] mm: Introduce memfd_restricted system call to create restricted user memory | From | "Nikunj A. Dadhania" <> |
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> +static struct file *restrictedmem_file_create(struct file *memfd) > +{ > + struct restrictedmem_data *data; > + struct address_space *mapping; > + struct inode *inode; > + struct file *file; > + > + data = kzalloc(sizeof(*data), GFP_KERNEL); > + if (!data) > + return ERR_PTR(-ENOMEM); > + > + data->memfd = memfd; > + mutex_init(&data->lock); > + INIT_LIST_HEAD(&data->notifiers); > + > + inode = alloc_anon_inode(restrictedmem_mnt->mnt_sb); > + if (IS_ERR(inode)) { > + kfree(data); > + return ERR_CAST(inode); > + }
alloc_anon_inode() uses new_pseudo_inode() to get the inode. As per the comment, new inode is not added to the superblock s_inodes list.
/** * new_inode_pseudo - obtain an inode * @sb: superblock * * Allocates a new inode for given superblock. * Inode wont be chained in superblock s_inodes list * This means : * - fs can't be unmount * - quotas, fsnotify, writeback can't work */
So the restrictedmem_error_page will not find the inode as it was never added to the s_inodes list.
We might need to add the inode after allocating.
inode_sb_list_add(inode);
> +void restrictedmem_error_page(struct page *page, struct address_space *mapping) > +{ > + struct super_block *sb = restrictedmem_mnt->mnt_sb; > + struct inode *inode, *next; > + > + if (!shmem_mapping(mapping)) > + return; > + > + spin_lock(&sb->s_inode_list_lock); > + list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) { > + struct restrictedmem_data *data = inode->i_mapping->private_data; > + struct file *memfd = data->memfd; > + > + if (memfd->f_mapping == mapping) { > + pgoff_t start, end; > + > + spin_unlock(&sb->s_inode_list_lock); > + > + start = page->index; > + end = start + thp_nr_pages(page); > + restrictedmem_notifier_error(data, start, end); > + return; > + } > + } > + spin_unlock(&sb->s_inode_list_lock); > +}
Regards Nikunj
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