[PATCH 6.1 135/197] nilfs2: fix data corruption in dsync block recovery for small block sizes

Greg Kroah-Hartman
2024-02-20T21:05:54Z

From: Ryusuke Konishi <konishi.ryusuke@gmail.com>

commit 67b8bcbaed4777871bb0dcc888fb02a614a98ab1 upstream.

The helper function nilfs_recovery_copy_block() of
nilfs_recovery_dsync_blocks(), which recovers data from logs created by
data sync writes during a mount after an unclean shutdown, incorrectly
calculates the on-page offset when copying repair data to the file's page
cache. In environments where the block size is smaller than the page
size, this flaw can cause data corruption and leak uninitialized memory
bytes during the recovery process.

Fix these issues by correcting this byte offset calculation on the page.

Link: https://lkml.kernel.org/r/20240124121936.10575-1-konishi.ryusuke@gmail.com
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/nilfs2/recovery.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

--- a/fs/nilfs2/recovery.c
+++ b/fs/nilfs2/recovery.c
@@ -472,9 +472,10 @@ static int nilfs_prepare_segment_for_rec

static int nilfs_recovery_copy_block(struct the_nilfs *nilfs,
struct nilfs_recovery_block *rb,
- struct page *page)
+ loff_t pos, struct page *page)
{
struct buffer_head *bh_org;
+ size_t from = pos & ~PAGE_MASK;
void *kaddr;

bh_org = __bread(nilfs->ns_bdev, rb->blocknr, nilfs->ns_blocksize);
@@ -482,7 +483,7 @@ static int nilfs_recovery_copy_block(str
return -EIO;

kaddr = kmap_atomic(page);
- memcpy(kaddr + bh_offset(bh_org), bh_org->b_data, bh_org->b_size);
+ memcpy(kaddr + from, bh_org->b_data, bh_org->b_size);
kunmap_atomic(kaddr);
brelse(bh_org);
return 0;
@@ -521,7 +522,7 @@ static int nilfs_recover_dsync_blocks(st
goto failed_inode;
}

- err = nilfs_recovery_copy_block(nilfs, rb, page);
+ err = nilfs_recovery_copy_block(nilfs, rb, pos, page);
if (unlikely(err))
goto failed_page;