Re: [PATCH] ext4: ext4_bread usage audit
From: Andreas Dilger <hidden>
Date: 2012-09-25 06:38:03
On 2012-09-24, at 20:41, Carlos Maiolino [off-list ref] wrote:
Audit the usage of ext4_bread() due a possible misinterpretion of its return value. Focused on directory blocks, a NULL value returned from ext4_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 ext4_getblk() may lead to a zero'ed return value of ext4_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 ext4_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)
Note that in the "errors=continue" case, it is desirable to allow the Filesystem to continue even if a hole is found in the directory, at least for non-htree directories, since it is possible the the entry being looked up is in a different block.
quoted hunk ↗ jump to hunk
Signed-off-by: Carlos Maiolino <redacted> --- fs/ext4/namei.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 69 insertions(+), 11 deletions(-)diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index 2a42cc0..1d5619b 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c@@ -67,6 +67,11 @@ static struct buffer_head *ext4_append(handle_t *handle, bh = NULL; } } + if (!bh && !(*err)) { + *err = -EIO; + ext4_error(inode->i_sb, "Directory hole detected on inode %lu\n", + inode->i_ino); + } return bh;}@@ -696,8 +701,11 @@ dx_probe(const struct qstr *d_name, struct inode *dir, frame->entries = entries; frame->at = at; if (!indirect--) return frame; - if (!(bh = ext4_bread (NULL,dir, dx_get_block(at), 0, err))) + if (!(bh = ext4_bread (NULL,dir, dx_get_block(at), 0, err))) {
Please keep the original code style, do not Di the assignment inside the if() check. That is incorrect in several places in this patch.
quoted hunk ↗ jump to hunk
+ if (!(*err)) + *err = ERR_BAD_DX_DIR; goto fail2; + } at = entries = ((struct dx_node *) bh->b_data)->entries; if (!buffer_verified(bh) &&@@ -807,8 +815,15 @@ static int ext4_htree_next_block(struct inode *dir, __u32 hash, */ while (num_frames--) { if (!(bh = ext4_bread(NULL, dir, dx_get_block(p->at), - 0, &err))) + 0, &err))) { + if (!err) { + ext4_error(dir->i_sb, + "Directory hole detected on inode %lu\n", + dir->i_ino); + return -EIO; + } return err; /* Failure */ + } if (!buffer_verified(bh) && !ext4_dx_csum_verify(dir,@@ -843,8 +858,14 @@ static int htree_dirblock_to_tree(struct file *dir_file, dxtrace(printk(KERN_INFO "In htree dirblock_to_tree: block %lu\n", (unsigned long)block)); - if (!(bh = ext4_bread (NULL, dir, block, 0, &err))) + if (!(bh = ext4_bread (NULL, dir, block, 0, &err))) { + if (!err) { + err = -EIO; + ext4_error(dir->i_sb, "Directory hole detected on inode %lu\n", + dir->i_ino); + } return err; + } if (!buffer_verified(bh) && !ext4_dirent_csum_verify(dir, (struct ext4_dir_entry *)bh->b_data))@@ -1267,8 +1288,15 @@ static struct buffer_head * ext4_dx_find_entry(struct inode *dir, const struct q return NULL; do { block = dx_get_block(frame->at); - if (!(bh = ext4_bread(NULL, dir, block, 0, err))) + if (!(bh = ext4_bread(NULL, dir, block, 0, err))) { + if (!(*err)) { + *err = -EIO; + ext4_error(dir->i_sb, + "Directory hole detected on inode %lu\n", + dir->i_ino); + } goto errout; + } if (!buffer_verified(bh) && !ext4_dirent_csum_verify(dir,@@ -1801,9 +1829,15 @@ static int ext4_add_entry(handle_t *handle, struct dentry *dentry, } blocks = dir->i_size >> sb->s_blocksize_bits; for (block = 0; block < blocks; block++) { - bh = ext4_bread(handle, dir, block, 0, &retval); - if(!bh) + if (!(bh = ext4_bread(handle, dir, block, 0, &retval))) { + if (!retval) { + retval = -EIO; + ext4_error(inode->i_sb, + "Directory hole detected on inode %lu\n", + inode->i_ino); + } return retval; + } if (!buffer_verified(bh) && !ext4_dirent_csum_verify(dir, (struct ext4_dir_entry *)bh->b_data))@@ -1860,8 +1894,15 @@ static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry, entries = frame->entries; at = frame->at; - if (!(bh = ext4_bread(handle,dir, dx_get_block(frame->at), 0, &err))) + if (!(bh = ext4_bread(handle,dir, dx_get_block(frame->at), 0, &err))) { + if (!err) { + err = -EIO; + ext4_error(dir->i_sb, + "Directory hole detected on inode %lu\n", + dir->i_ino); + } goto cleanup; + } if (!buffer_verified(bh) && !ext4_dirent_csum_verify(dir, (struct ext4_dir_entry *)bh->b_data))@@ -2199,9 +2240,15 @@ retry: inode->i_op = &ext4_dir_inode_operations; inode->i_fop = &ext4_dir_operations; inode->i_size = EXT4_I(inode)->i_disksize = inode->i_sb->s_blocksize; - dir_block = ext4_bread(handle, inode, 0, 1, &err); - if (!dir_block) + if (!(dir_block = ext4_bread(handle, inode, 0, 1, &err))) { + if (!err) { + err = -EIO; + ext4_error(inode->i_sb, + "Directory hole detected on inode %lu\n", + inode->i_ino); + } goto out_clear_inode; + } BUFFER_TRACE(dir_block, "get_write_access"); err = ext4_journal_get_write_access(handle, dir_block); if (err)@@ -2318,6 +2365,11 @@ static int empty_dir(struct inode *inode) EXT4_ERROR_INODE(inode, "error %d reading directory " "lblock %u", err, lblock); + else + ext4_warning(inode->i_sb, + "bad directory (dir #%lu) - no data block", + inode->i_ino); + offset += sb->s_blocksize; continue; }@@ -2826,9 +2878,15 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry, goto end_rename; } retval = -EIO; - dir_bh = ext4_bread(handle, old_inode, 0, 0, &retval); - if (!dir_bh) + if(!(dir_bh = ext4_bread(handle, old_inode, 0, 0, &retval))) { + if (!retval) { + retval = -EIO; + ext4_error(old_inode->i_sb, + "Directory hole detected on inode %lu\n", + old_inode->i_ino); + } goto end_rename; + } if (!buffer_verified(dir_bh) && !ext4_dirent_csum_verify(old_inode, (struct ext4_dir_entry *)dir_bh->b_data))-- 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