e2fsck: do not read EA header beyond the end of an inode

e2fsck: do not read EA header beyond the end of an inode

In check_inode_extra_space(), if we attempt to read an EA header at
the end of the extra space, in a corrupted filesystem it may result in
a read beyond the bounds of the inode. Add a check to prevent this.

Reproduced by running ./test_one --valgrind f_write_ea_toobig_extra_isize.

Signed-off-by: Artemiy Volkov <artemiyv@acm.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: Darrick J. Wong <darrick.wong@oracle.com>