ocfs2: strict bound check before memcmp in ocfs2_xattr_find_entry()

ocfs2: strict bound check before memcmp in ocfs2_xattr_find_entry()

xattr in ocfs2 maybe 'non-indexed', which saved with additional space
requested.  It's better to check if the memory is out of bound before
memcmp, although this possibility mainly comes from crafted poisonous
images.

Link: https://lkml.kernel.org/r/20240520024024.1976129-2-joseph.qi@linux.alibaba.com
Signed-off-by: Ferry Meng <mengferry@linux.alibaba.com>
Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Reported-by: lei lu <llfamsec@gmail.com>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Gang He <ghe@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Jun Piao <piaojun@huawei.com>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Mark Fasheh <mark@fasheh.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>