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Message-ID: <20121004124212.GG4641@quack.suse.cz>
Date: Thu, 4 Oct 2012 14:42:12 +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 [V2]
On Tue 02-10-12 23:59:23, 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)
>
> V2: It adds a wrapper function ext3_dir_bread() to check for directory holes
> when reading blocks for a directory inode, and callers of ext3_bread() to read
> directory blocks were replaced by this wrapper.
>
> Signed-off-by: Carlos Maiolino <cmaiolino@...hat.com>
Oh, I see you already sent V2. Thanks. I've put the patch to my tree.
Honza
> ---
> fs/ext3/namei.c | 36 +++++++++++++++++++-----------------
> fs/ext3/namei.h | 19 +++++++++++++++++++
> 2 files changed, 38 insertions(+), 17 deletions(-)
>
> diff --git a/fs/ext3/namei.c b/fs/ext3/namei.c
> index 7f6c938..0eecf4d 100644
> --- a/fs/ext3/namei.c
> +++ b/fs/ext3/namei.c
> @@ -46,8 +46,7 @@ static struct buffer_head *ext3_append(handle_t *handle,
>
> *block = inode->i_size >> inode->i_sb->s_blocksize_bits;
>
> - bh = ext3_bread(handle, inode, *block, 1, err);
> - if (bh) {
> + if ((bh = ext3_dir_bread(handle, inode, *block, 1, err))) {
> inode->i_size += inode->i_sb->s_blocksize;
> EXT3_I(inode)->i_disksize = inode->i_size;
> *err = ext3_journal_get_write_access(handle, bh);
> @@ -339,8 +338,10 @@ 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_dir_bread(NULL, dir, 0, 0, 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 +437,10 @@ 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_dir_bread(NULL, dir, dx_get_block(at), 0, 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__,
> @@ -535,8 +538,8 @@ static int ext3_htree_next_block(struct inode *dir, __u32 hash,
> * block so no check is necessary
> */
> while (num_frames--) {
> - if (!(bh = ext3_bread(NULL, dir, dx_get_block(p->at),
> - 0, &err)))
> + if (!(bh = ext3_dir_bread(NULL, dir, dx_get_block(p->at),
> + 0, &err)))
> return err; /* Failure */
> p++;
> brelse (p->bh);
> @@ -562,7 +565,8 @@ 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_dir_bread(NULL, dir, block, 0, &err)))
> return err;
>
> de = (struct ext3_dir_entry_2 *) bh->b_data;
> @@ -976,7 +980,7 @@ 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_dir_bread (NULL, dir, block, 0, err)))
> goto errout;
>
> retval = search_dirblock(bh, dir, entry,
> @@ -1458,9 +1462,9 @@ 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_dir_bread(handle, dir, block, 0, &retval)))
> return retval;
> +
> retval = add_dirent_to_buf(handle, dentry, inode, NULL, bh);
> if (retval != -ENOSPC)
> return retval;
> @@ -1500,7 +1504,7 @@ 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_dir_bread(handle, dir, dx_get_block(frame->at), 0, &err)))
> goto cleanup;
>
> BUFFER_TRACE(bh, "get_write_access");
> @@ -1790,8 +1794,7 @@ retry:
> inode->i_op = &ext3_dir_inode_operations;
> 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 = ext3_dir_bread(handle, inode, 0, 1, &err)))
> goto out_clear_inode;
>
> BUFFER_TRACE(dir_block, "get_write_access");
> @@ -1859,7 +1862,7 @@ static int empty_dir (struct inode * inode)
>
> sb = inode->i_sb;
> if (inode->i_size < EXT3_DIR_REC_LEN(1) + EXT3_DIR_REC_LEN(2) ||
> - !(bh = ext3_bread (NULL, inode, 0, 0, &err))) {
> + !(bh = ext3_dir_bread(NULL, inode, 0, 0, &err))) {
> if (err)
> ext3_error(inode->i_sb, __func__,
> "error %d reading directory #%lu offset 0",
> @@ -1890,9 +1893,8 @@ static int empty_dir (struct inode * inode)
> (void *) de >= (void *) (bh->b_data+sb->s_blocksize)) {
> err = 0;
> brelse (bh);
> - bh = ext3_bread (NULL, inode,
> - offset >> EXT3_BLOCK_SIZE_BITS(sb), 0, &err);
> - if (!bh) {
> + if (!(bh = ext3_dir_bread (NULL, inode,
> + offset >> EXT3_BLOCK_SIZE_BITS(sb), 0, &err))) {
> if (err)
> ext3_error(sb, __func__,
> "error %d reading directory"
> diff --git a/fs/ext3/namei.h b/fs/ext3/namei.h
> index f2ce2b0..46304d8 100644
> --- a/fs/ext3/namei.h
> +++ b/fs/ext3/namei.h
> @@ -6,3 +6,22 @@
> */
>
> extern struct dentry *ext3_get_parent(struct dentry *child);
> +
> +static inline struct buffer_head *ext3_dir_bread(handle_t *handle,
> + struct inode *inode,
> + int block, int create,
> + int *err)
> +{
> + struct buffer_head *bh;
> +
> + bh = ext3_bread(handle, inode, block, create, err);
> +
> + if (!bh && !(*err)) {
> + *err = -EIO;
> + ext3_error(inode->i_sb, __func__,
> + "Directory hole detected on inode %lu\n",
> + inode->i_ino);
> + return NULL;
> + }
> + return bh;
> +}
> --
> 1.7.11.4
>
> --
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--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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