Patchwork [2/2] ext3: ext3_bread usage audit

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Submitter Carlos Maiolino
Date Oct. 1, 2012, 7:50 p.m.
Message ID <1349121055-8168-3-git-send-email-cmaiolino@redhat.com>
Download mbox | patch
Permalink /patch/188341/
State Not Applicable
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Comments

Carlos Maiolino - Oct. 1, 2012, 7:50 p.m.
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)

Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
---
 fs/ext3/namei.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 66 insertions(+), 9 deletions(-)
Jan Kara - Oct. 2, 2012, 1:55 p.m.
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@redhat.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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Carlos Maiolino - Oct. 2, 2012, 2:27 p.m.
Hi Jan
On Tue, Oct 02, 2012 at 03:55:13PM +0200, Jan Kara wrote:
> 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!
>
I thought about a kind of handler too, but haven't done something like that by
Ted's suggestion. Please see thread
http://marc.info/?l=linux-ext4&m=134827512716575&w=2

But I can work on a kind of wrapper for ext3 if this is ok for you and send a V2
version of this patch.

Cheers,
Carlos
Jan Kara - Oct. 4, 2012, 12:38 p.m.
On Tue 02-10-12 11:27:23, Carlos Maiolino wrote:
> Hi Jan
> On Tue, Oct 02, 2012 at 03:55:13PM +0200, Jan Kara wrote:
> > 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!
> >
  Please use reply-to-all when replying next time. It makes me see the
email much faster and reply cannot get lost in mailing list traffic...

> I thought about a kind of handler too, but haven't done something like that by
> Ted's suggestion. Please see thread
> http://marc.info/?l=linux-ext4&m=134827512716575&w=2
> 
> But I can work on a kind of wrapper for ext3 if this is ok for you and send a V2
> version of this patch.
  I see. Still I'd rather have the helper function. So please send V2.
Thanks.

								Honza

Patch

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;
 			}