tree 0c0100945f74ad1d68b9b546e1929cfcb67e9095
parent d3a23e1678a5827c38ed8a465ad91d65e59fa911
author Nick Piggin <npiggin@kernel.dk> 1294382956 +1100
committer Nick Piggin <npiggin@kernel.dk> 1294383016 +1100

fs: d_validate fixes

d_validate has been broken for a long time.

kmem_ptr_validate does not guarantee that a pointer can be dereferenced
if it can go away at any time. Even rcu_read_lock doesn't help, because
the pointer might be queued in RCU callbacks but not executed yet.

So the parent cannot be checked, nor the name hashed. The dentry pointer
can not be touched until it can be verified under lock. Hashing simply
cannot be used.

Instead, verify the parent/child relationship by traversing parent's
d_child list. It's slow, but only ncpfs and the destaged smbfs care
about it, at this point.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>