Dan Aloni reports that he was able to hit a use-after-free bug if a FREE_STATEID operation gets delayed for whatever reason. Fix this by bumping the refcount of the 'struct nfs_server' object for the duration of the FREE_STATEID so it doesn't get cleaned up from underneath us while operations are still in flight. Reported-by: Dan Aloni <dan.aloni@vastdata.com> Fixes: 7c1d5fae4a87 ("NFSv4: Convert nfs41_free_stateid to use an asynchronous RPC call") Tested-by: Dan Aloni <dan.aloni@vastdata.com> Signed-off-by: Anna Schumaker <anna.schumaker@hammerspace.com> Signed-off-by: Zhou Minqiang <zhouminqiang2@huawei.com> --- fs/nfs/nfs4proc.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index f7163d9de438..83f758c9ada6 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -10383,6 +10383,7 @@ static void nfs41_free_stateid_release(void *calldata) struct nfs_free_stateid_data *data = calldata; struct nfs_client *clp = data->server->nfs_client; + nfs_sb_deactive(data->server->super); nfs_put_client(clp); kfree(calldata); } @@ -10424,6 +10425,10 @@ static int nfs41_free_stateid(struct nfs_server *server, if (!refcount_inc_not_zero(&clp->cl_count)) return -EIO; + if (!nfs_sb_active(server->super)) { + nfs_put_client(clp); + return -EIO; + } nfs4_state_protect(server->nfs_client, NFS_SP4_MACH_CRED_STATEID, &task_setup.rpc_client, &msg); -- 2.52.0