From e4465fdaeb3f7b5ef47f389d3eac76db79ff20d8 Mon Sep 17 00:00:00 2001 From: Michael Halcrow Date: Tue, 4 Mar 2008 14:29:24 -0800 Subject: [PATCH] eCryptfs: make ecryptfs_prepare_write decrypt the page When the page is not up to date, ecryptfs_prepare_write() should be acting much like ecryptfs_readpage(). This includes the painfully obvious step of actually decrypting the page contents read from the lower encrypted file. Note that this patch resolves a bug in eCryptfs in 2.6.24 that one can produce with these steps: # mount -t ecryptfs /secret /secret # echo "abc" > /secret/file.txt # umount /secret # mount -t ecryptfs /secret /secret # echo "def" >> /secret/file.txt # cat /secret/file.txt Without this patch, the resulting data returned from cat is likely to be something other than "abc\ndef\n". (Thanks to Benedikt Driessen for reporting this.) Signed-off-by: Michael Halcrow Cc: Benedikt Driessen Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/ecryptfs/mmap.c | 102 +++++++++++++++++++++++++++++++++------------ 1 file changed, 76 insertions(+), 26 deletions(-) diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c index dc74b18614..6df1debdcc 100644 --- a/fs/ecryptfs/mmap.c +++ b/fs/ecryptfs/mmap.c @@ -263,52 +263,102 @@ out: return 0; } -/* This function must zero any hole we create */ +/** + * ecryptfs_prepare_write + * @file: The eCryptfs file + * @page: The eCryptfs page + * @from: The start byte from which we will write + * @to: The end byte to which we will write + * + * This function must zero any hole we create + * + * Returns zero on success; non-zero otherwise + */ static int ecryptfs_prepare_write(struct file *file, struct page *page, unsigned from, unsigned to) { - int rc = 0; loff_t prev_page_end_size; + int rc = 0; if (!PageUptodate(page)) { - rc = ecryptfs_read_lower_page_segment(page, page->index, 0, - PAGE_CACHE_SIZE, - page->mapping->host); - if (rc) { - printk(KERN_ERR "%s: Error attemping to read lower " - "page segment; rc = [%d]\n", __FUNCTION__, rc); - ClearPageUptodate(page); - goto out; - } else + struct ecryptfs_crypt_stat *crypt_stat = + &ecryptfs_inode_to_private( + file->f_path.dentry->d_inode)->crypt_stat; + + if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED) + || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) { + rc = ecryptfs_read_lower_page_segment( + page, page->index, 0, PAGE_CACHE_SIZE, + page->mapping->host); + if (rc) { + printk(KERN_ERR "%s: Error attemping to read " + "lower page segment; rc = [%d]\n", + __FUNCTION__, rc); + ClearPageUptodate(page); + goto out; + } else + SetPageUptodate(page); + } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) { + if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) { + rc = ecryptfs_copy_up_encrypted_with_header( + page, crypt_stat); + if (rc) { + printk(KERN_ERR "%s: Error attempting " + "to copy the encrypted content " + "from the lower file whilst " + "inserting the metadata from " + "the xattr into the header; rc " + "= [%d]\n", __FUNCTION__, rc); + ClearPageUptodate(page); + goto out; + } + SetPageUptodate(page); + } else { + rc = ecryptfs_read_lower_page_segment( + page, page->index, 0, PAGE_CACHE_SIZE, + page->mapping->host); + if (rc) { + printk(KERN_ERR "%s: Error reading " + "page; rc = [%d]\n", + __FUNCTION__, rc); + ClearPageUptodate(page); + goto out; + } + SetPageUptodate(page); + } + } else { + rc = ecryptfs_decrypt_page(page); + if (rc) { + printk(KERN_ERR "%s: Error decrypting page " + "at index [%ld]; rc = [%d]\n", + __FUNCTION__, page->index, rc); + ClearPageUptodate(page); + goto out; + } SetPageUptodate(page); + } } - prev_page_end_size = ((loff_t)page->index << PAGE_CACHE_SHIFT); - - /* - * If creating a page or more of holes, zero them out via truncate. - * Note, this will increase i_size. - */ + /* If creating a page or more of holes, zero them out via truncate. + * Note, this will increase i_size. */ if (page->index != 0) { if (prev_page_end_size > i_size_read(page->mapping->host)) { rc = ecryptfs_truncate(file->f_path.dentry, prev_page_end_size); if (rc) { - printk(KERN_ERR "Error on attempt to " + printk(KERN_ERR "%s: Error on attempt to " "truncate to (higher) offset [%lld];" - " rc = [%d]\n", prev_page_end_size, rc); + " rc = [%d]\n", __FUNCTION__, + prev_page_end_size, rc); goto out; } } } - /* - * Writing to a new page, and creating a small hole from start of page? - * Zero it out. - */ - if ((i_size_read(page->mapping->host) == prev_page_end_size) && - (from != 0)) { + /* Writing to a new page, and creating a small hole from start + * of page? Zero it out. */ + if ((i_size_read(page->mapping->host) == prev_page_end_size) + && (from != 0)) zero_user(page, 0, PAGE_CACHE_SIZE); - } out: return rc; } -- 2.39.5