From: Jan Kara Subject: Re: [PATCH 2/2] ext3: ext3_bread usage audit Date: Tue, 2 Oct 2012 15:55:13 +0200 Message-ID: <20121002135513.GE22777@quack.suse.cz> References: <1349121055-8168-1-git-send-email-cmaiolino@redhat.com> <1349121055-8168-3-git-send-email-cmaiolino@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org To: Carlos Maiolino Return-path: Received: from cantor2.suse.de ([195.135.220.15]:59101 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753654Ab2JBNzP (ORCPT ); Tue, 2 Oct 2012 09:55:15 -0400 Content-Disposition: inline In-Reply-To: <1349121055-8168-3-git-send-email-cmaiolino@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon 01-10-12 16:50:55, Carlos Maiolino wrote: > This is the ext3 version of the same patch applied to Ext4, where such goal is > to audit the usage of ext3_bread() due a possible misinterpretion of its return > value. > > Focused on directory blocks, a NULL value returned from ext3_bread() means a > hole, which cannot exist into a directory inode. It can pass undetected after a > fix in an uninitialized error variable. > > The (now) initialized variable into ext3_getblk() may lead to a zero'ed return > value of ext3_bread() to its callers, which can make the caller do not detect > the hole in the directory inode. > > This checks for directory holes when buffer_head and error value are both > zero'ed returning -EIO to their callers > > Some ext3_bread() callers do not needed any changes either because they already > had its own hole detector paths or because these are deprecaded (like > dx_show_entries) Umm, can you wrap the check for hole + error message in a helper function like ext3_dir_bread() please? That would save us quite some dupplication.. Thanks! Honza > > Signed-off-by: Carlos Maiolino > --- > fs/ext3/namei.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++------- > 1 file changed, 66 insertions(+), 9 deletions(-) > > diff --git a/fs/ext3/namei.c b/fs/ext3/namei.c > index 7f6c938..8e56c2cc 100644 > --- a/fs/ext3/namei.c > +++ b/fs/ext3/namei.c > @@ -56,6 +56,11 @@ static struct buffer_head *ext3_append(handle_t *handle, > bh = NULL; > } > } > + if (!bh && !(*err)) { > + *err = -EIO; > + ext3_error(inode->i_sb, __func__, > + "Directory hole detected on inode %lu\n", inode->i_ino); > + } > return bh; > } > > @@ -339,8 +344,11 @@ dx_probe(struct qstr *entry, struct inode *dir, > u32 hash; > > frame->bh = NULL; > - if (!(bh = ext3_bread (NULL,dir, 0, 0, err))) > + if (!(bh = ext3_bread (NULL,dir, 0, 0, err))) { > + if (!(*err)) > + *err = ERR_BAD_DX_DIR; > goto fail; > + } > root = (struct dx_root *) bh->b_data; > if (root->info.hash_version != DX_HASH_TEA && > root->info.hash_version != DX_HASH_HALF_MD4 && > @@ -436,8 +444,11 @@ dx_probe(struct qstr *entry, struct inode *dir, > frame->entries = entries; > frame->at = at; > if (!indirect--) return frame; > - if (!(bh = ext3_bread (NULL,dir, dx_get_block(at), 0, err))) > + if (!(bh = ext3_bread (NULL,dir, dx_get_block(at), 0, err))) { > + if (!(*err)) > + *err = ERR_BAD_DX_DIR; > goto fail2; > + } > at = entries = ((struct dx_node *) bh->b_data)->entries; > if (dx_get_limit(entries) != dx_node_limit (dir)) { > ext3_warning(dir->i_sb, __func__, > @@ -536,8 +547,15 @@ static int ext3_htree_next_block(struct inode *dir, __u32 hash, > */ > while (num_frames--) { > if (!(bh = ext3_bread(NULL, dir, dx_get_block(p->at), > - 0, &err))) > + 0, &err))) { > + if (!err) { > + ext3_error(dir->i_sb, __func__, > + "Directory hole detected on inode %lu\n", > + dir->i_ino); > + return -EIO; > + } > return err; /* Failure */ > + } > p++; > brelse (p->bh); > p->bh = bh; > @@ -562,8 +580,15 @@ static int htree_dirblock_to_tree(struct file *dir_file, > int err = 0, count = 0; > > dxtrace(printk("In htree dirblock_to_tree: block %d\n", block)); > - if (!(bh = ext3_bread (NULL, dir, block, 0, &err))) > + if (!(bh = ext3_bread (NULL, dir, block, 0, &err))) { > + if (!err) { > + ext3_error(dir->i_sb, __func__, > + "Directory hole detected on inode %lu\n", > + dir->i_ino); > + return -EIO; > + } > return err; > + } > > de = (struct ext3_dir_entry_2 *) bh->b_data; > top = (struct ext3_dir_entry_2 *) ((char *) de + > @@ -976,8 +1001,15 @@ static struct buffer_head * ext3_dx_find_entry(struct inode *dir, > return NULL; > do { > block = dx_get_block(frame->at); > - if (!(bh = ext3_bread (NULL,dir, block, 0, err))) > + if (!(bh = ext3_bread (NULL,dir, block, 0, err))) { > + if (!(*err)) { > + *err = -EIO; > + ext3_error(dir->i_sb, __func__, > + "Directory hole detected on inode %lu\n", > + dir->i_ino); > + } > goto errout; > + } > > retval = search_dirblock(bh, dir, entry, > block << EXT3_BLOCK_SIZE_BITS(sb), > @@ -1458,9 +1490,15 @@ static int ext3_add_entry (handle_t *handle, struct dentry *dentry, > } > blocks = dir->i_size >> sb->s_blocksize_bits; > for (block = 0; block < blocks; block++) { > - bh = ext3_bread(handle, dir, block, 0, &retval); > - if(!bh) > + if (!(bh = ext3_bread(handle, dir, block, 0, &retval))) { > + if (!retval) { > + retval = -EIO; > + ext3_error(dir->i_sb, __func__, > + "Directory hole detected on inode %lu\n", > + dir->i_ino); > + } > return retval; > + } > retval = add_dirent_to_buf(handle, dentry, inode, NULL, bh); > if (retval != -ENOSPC) > return retval; > @@ -1500,8 +1538,15 @@ static int ext3_dx_add_entry(handle_t *handle, struct dentry *dentry, > entries = frame->entries; > at = frame->at; > > - if (!(bh = ext3_bread(handle,dir, dx_get_block(frame->at), 0, &err))) > + if (!(bh = ext3_bread(handle,dir, dx_get_block(frame->at), 0, &err))) { > + if (!err) { > + err = -EIO; > + ext3_error(dir->i_sb, __func__, > + "Directory hole detected on inode %lu\n", > + dir->i_ino); > + } > goto cleanup; > + } > > BUFFER_TRACE(bh, "get_write_access"); > err = ext3_journal_get_write_access(handle, bh); > @@ -1791,8 +1836,15 @@ retry: > inode->i_fop = &ext3_dir_operations; > inode->i_size = EXT3_I(inode)->i_disksize = inode->i_sb->s_blocksize; > dir_block = ext3_bread (handle, inode, 0, 1, &err); > - if (!dir_block) > + if (!dir_block) { > + if (!err) { > + err = -EIO; > + ext3_error(inode->i_sb, __func__, > + "Directory hole detected on inode %lu\n", > + inode->i_ino); > + } > goto out_clear_inode; > + } > > BUFFER_TRACE(dir_block, "get_write_access"); > err = ext3_journal_get_write_access(handle, dir_block); > @@ -1898,6 +1950,11 @@ static int empty_dir (struct inode * inode) > "error %d reading directory" > " #%lu offset %lu", > err, inode->i_ino, offset); > + else > + ext3_warning(inode->i_sb, __func__, > + "bad directory (dir #%lu) - no data block", > + inode->i_ino); > + > offset += sb->s_blocksize; > continue; > } > -- > 1.7.11.4 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html