From 1e81d6c383da155e93feccb2ac87c2ff64872d11 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Thu, 13 Jun 2024 17:02:34 +0200 Subject: [PATCH] ext4: avoid writing unitialized memory to disk in EA inodes [ Upstream commit 65121eff3e4c8c90f8126debf3c369228691c591 ] If the extended attribute size is not a multiple of block size, the last block in the EA inode will have uninitialized tail which will get written to disk. We will never expose the data to userspace but still this is not a good practice so just zero out the tail of the block as it isn't going to cause a noticeable performance overhead. Fixes: e50e5129f384 ("ext4: xattr-in-inode support") Reported-by: syzbot+9c1fe13fcb51574b249b@syzkaller.appspotmail.com Reported-by: Hugh Dickins Signed-off-by: Jan Kara Link: https://patch.msgid.link/20240613150234.25176-1-jack@suse.cz Signed-off-by: Theodore Ts'o Signed-off-by: Sasha Levin --- fs/ext4/xattr.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c index 41b4630b17d6..c58cbe9f7809 100644 --- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c @@ -1433,6 +1433,12 @@ retry: goto out; memcpy(bh->b_data, buf, csize); + /* + * Zero out block tail to avoid writing uninitialized memory + * to disk. + */ + if (csize < blocksize) + memset(bh->b_data + csize, 0, blocksize - csize); set_buffer_uptodate(bh); ext4_handle_dirty_metadata(handle, ea_inode, bh);