This is a note to let you know that I've just added the patch titled
ext4: make sure ext4_append() always allocates new block
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ext4-make-sure-ext4_append-always-allocates-new-block.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b8a04fe77ef1360fbf73c80fddbdfeaa9407ed1b Mon Sep 17 00:00:00 2001
From: Lukas Czerner <lczerner@xxxxxxxxxx>
Date: Mon, 4 Jul 2022 16:27:21 +0200
Subject: ext4: make sure ext4_append() always allocates new block
From: Lukas Czerner <lczerner@xxxxxxxxxx>
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@xxxxxxxxxx
Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx>
Link: https://lore.kernel.org/r/20220704142721.157985-2-lczerner@xxxxxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ext4/namei.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -53,6 +53,7 @@ static struct buffer_head *ext4_append(h
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(h
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))
Patches currently in stable-queue which might be from lczerner@xxxxxxxxxx are
queue-4.19/ext4-make-sure-ext4_append-always-allocates-new-block.patch
