From: "J. Bruce Fields" <bfields@xxxxxxxxxx> We add the new state to the nfsi->open_states list, making it potentially visible to other threads, before we've finished initializing it. That wasn't a problem when all the readers were also taking the i_lock (as we do here), but since we switched to RCU, there's now a possibility that a reader could see the partially initialized state. Symptoms observed were a crash when another thread called nfs4_get_valid_delegation() on a NULL inode. Fixes: 9ae075fdd190 "NFSv4: Convert open state lookup to use RCU" Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx> --- fs/nfs/nfs4state.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c index ac93715c05a4..a8dc25ce48bb 100644 --- a/fs/nfs/nfs4state.c +++ b/fs/nfs/nfs4state.c @@ -734,9 +734,9 @@ nfs4_get_open_state(struct inode *inode, struct nfs4_state_owner *owner) state = new; state->owner = owner; atomic_inc(&owner->so_count); - list_add_rcu(&state->inode_states, &nfsi->open_states); ihold(inode); state->inode = inode; + list_add_rcu(&state->inode_states, &nfsi->open_states); spin_unlock(&inode->i_lock); /* Note: The reclaim code dictates that we add stateless * and read-only stateids to the end of the list */ -- 2.26.2
