From 48d149dc32aa8887e7265be269931853807fa1c7 Mon Sep 17 00:00:00 2001
From: Lukas Czerner <lczerner@redhat.com>
Date: Wed, 7 Sep 2022 09:24:54 +0000
Subject: [PATCH] ext4: make sure ext4_append() always allocates new block
stable inclusion
from stable-v4.19.256
commit 4816177c9f154594c8a841ed95b883eb07e4d6ce
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5Q0SQ
CVE: NA
--------------------------------
commit b8a04fe77ef1360fbf73c80fddbdfeaa9407ed1b upstream.
ext4_append() must always allocate a new block, otherwise we run the
risk of overwriting existing directory block corrupting the directory
tree in the process resulting in all manner of problems later on.
Add a sanity check to see if the logical block is already allocated and
error out if it is.
Cc: stable@kernel.org
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20220704142721.157985-2-lczerner@redhat.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>
---
fs/ext4/namei.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 134fef1f6edc..b2d4fb82e8f4 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -53,6 +53,7 @@ static struct buffer_head *ext4_append(handle_t *handle,
struct inode *inode,
ext4_lblk_t *block)
{
+ struct ext4_map_blocks map;
struct buffer_head *bh;
int err;
@@ -62,6 +63,21 @@ static struct buffer_head *ext4_append(handle_t *handle,
return ERR_PTR(-ENOSPC);
*block = inode->i_size >> inode->i_sb->s_blocksize_bits;
+ map.m_lblk = *block;
+ map.m_len = 1;
+
+ /*
+ * We're appending new directory block. Make sure the block is not
+ * allocated yet, otherwise we will end up corrupting the
+ * directory.
+ */
+ err = ext4_map_blocks(NULL, inode, &map, 0);
+ if (err < 0)
+ return ERR_PTR(err);
+ if (err) {
+ EXT4_ERROR_INODE(inode, "Logical block already allocated");
+ return ERR_PTR(-EFSCORRUPTED);
+ }
bh = ext4_bread(handle, inode, *block, EXT4_GET_BLOCKS_CREATE);
if (IS_ERR(bh))
--
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