ext4: disallow hard-linked directory in ext4_lookup
ext4: disallow hard-linked directory in ext4_lookup

A hard-linked directory to its parent can cause the VFS to deadlock,
and is a sign of a corrupted file system.  So detect this case in
ext4_lookup(), before the rmdir() lockup scenario can take place.

Signed-off-by: Andreas Dilger <fd4823dd86d134508df78a168e24c446ce7699f3@dilger.ca>
Signed-off-by: "Theodore Ts'o" <4ed386e0495d3e109932df055831d9ec2f824927@mit.edu>
Cc: 4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@kernel.org

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas