From: Jan Kara Date: Thu, 13 Jun 2024 15:02:34 +0000 (+0200) Subject: ext4: avoid writing unitialized memory to disk in EA inodes X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=65121eff3e4c8c90f8126debf3c369228691c591;p=linux.git ext4: avoid writing unitialized memory to disk in EA inodes 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 --- diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c index 6460879b9fcb..46ce2f21fef9 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);