| From 7276c120114cc14209c66eccb0f0140a9fdc09b9 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Mon, 11 May 2020 10:02:48 -0400 |
| Subject: nfs: fix NULL deference in nfs4_get_valid_delegation |
| |
| From: J. Bruce Fields <bfields@redhat.com> |
| |
| [ Upstream commit 29fe839976266bc7c55b927360a1daae57477723 ] |
| |
| 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" |
| Reviewed-by: Seiichi Ikarashi <s.ikarashi@fujitsu.com> |
| Tested-by: Daisuke Matsuda <matsuda-daisuke@fujitsu.com> |
| Tested-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com> |
| Signed-off-by: J. Bruce Fields <bfields@redhat.com> |
| Cc: stable@vger.kernel.org # v4.20+ |
| Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| 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 f7723d221945b..459c7fb5d103a 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 */ |
| -- |
| 2.20.1 |
| |