Hello, How about adding Cc: stable@xxxxxxxxxxxxxxx in the sign-off area? 9ae075fdd190 "NFSv4: Convert open state lookup to use RCU" was merged to v4.20 and some stable tree have 9ae075fdd190. On Mon, May 11, 2020 at 10:02:48AM -0400, bfields@xxxxxxxxxxxx wrote: > 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, resulting in an oops like: > > BUG: unable to handle page fault for address: ffffffffffffffb0 ... > RIP: 0010:nfs4_get_valid_delegation+0x6/0x30 [nfsv4] ... > Call Trace: > nfs4_open_prepare+0x80/0x1c0 [nfsv4] > __rpc_execute+0x75/0x390 [sunrpc] > ? finish_task_switch+0x75/0x260 > rpc_async_schedule+0x29/0x40 [sunrpc] > process_one_work+0x1ad/0x370 > worker_thread+0x30/0x390 > ? create_worker+0x1a0/0x1a0 > kthread+0x10c/0x130 > ? kthread_park+0x80/0x80 > ret_from_fork+0x22/0x30 > > Fixes: 9ae075fdd190 "NFSv4: Convert open state lookup to use RCU" Cc: stable@xxxxxxxxxxxxxxx # 4.20.x- Thanks! Masa > Reviewed-by: Seiichi Ikarashi <s.ikarashi@xxxxxxxxxxx> > Tested-by: Daisuke Matsuda <matsuda-daisuke@xxxxxxxxxxx> > Tested-by: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx> > Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx> > --- > fs/nfs/nfs4state.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > > I do have a patch including the tags and oops provided by Masayoshi > > Mizuma, if you'd like to take that instead. See followup.--b. > > Here you go. > > diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c > index f7723d221945..459c7fb5d103 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 >
