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Date: Mon, 1 Oct 2012 16:50:55 -0300
From: Carlos Maiolino <cmaiolino@...hat.com>
To: linux-ext4@...r.kernel.org
Subject: [PATCH 2/2] ext3: ext3_bread usage audit
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@...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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