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Date: Tue, 2 Oct 2012 15:55:13 +0200
From: Jan Kara <jack@...e.cz>
To: Carlos Maiolino <cmaiolino@...hat.com>
Cc: linux-ext4@...r.kernel.org
Subject: Re: [PATCH 2/2] ext3: ext3_bread usage audit
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 <cmaiolino@...hat.com>
> ---
> 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
>
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