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| author | J. Bruce Fields <bfields@redhat.com> | 2020-05-11 10:02:48 -0400 |
|---|---|---|
| committer | Trond Myklebust <trond.myklebust@hammerspace.com> | 2020-05-11 14:05:58 -0400 |
| commit | 29fe839976266bc7c55b927360a1daae57477723 (patch) | |
| tree | 3cb85d4607d3afc181412975faa17e0f467e7808 | |
| parent | 31e9a7f353526bbe53165a292f8ea9695ead3168 (diff) | |
| download | linux-29fe839976266bc7c55b927360a1daae57477723.tar.bz2 | |
nfs: fix NULL deference in nfs4_get_valid_delegation
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>
| -rw-r--r-- | fs/nfs/nfs4state.c | 2 |
1 files changed, 1 insertions, 1 deletions
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 */ |