[PATCH 1/2] lpfc: nvme: avoid hang / use-after-free when destroying localport

[Ewan D. Milne]

We cannot wait on a completion object in the lpfc_nvme_lport structure
in the _destroy_localport() code path because the NVMe/fc transport will
free that structure immediately after the .localport_delete() callback.
This results in a use-after-free, and a hang if slub_debug=FZPU is enabled.

Fix this by putting the completion on the stack.

Signed-off-by: Ewan D. Milne <emi...@redhat.com>
---
 drivers/scsi/lpfc/lpfc_nvme.c | 16 +++++++++-------
 drivers/scsi/lpfc/lpfc_nvme.h |  2 +-
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/lpfc/lpfc_nvme.c b/drivers/scsi/lpfc/lpfc_nvme.c
index 4c66b19..8c9f790 100644
--- a/drivers/scsi/lpfc/lpfc_nvme.c
+++ b/drivers/scsi/lpfc/lpfc_nvme.c
@@ -297,7 +297,8 @@ lpfc_nvme_localport_delete(struct nvme_fc_local_port 
*localport)
                         lport);
 
        /* release any threads waiting for the unreg to complete */
-       complete(&lport->lport_unreg_done);
+       if (lport->vport->localport)
+               complete(lport->lport_unreg_cmp);
 }
 
 /* lpfc_nvme_remoteport_delete
@@ -2545,7 +2546,8 @@ lpfc_nvme_create_localport(struct lpfc_vport *vport)
  */
 void
 lpfc_nvme_lport_unreg_wait(struct lpfc_vport *vport,
-                          struct lpfc_nvme_lport *lport)
+                          struct lpfc_nvme_lport *lport,
+                          struct completion *lport_unreg_cmp)
 {
 #if (IS_ENABLED(CONFIG_NVME_FC))
        u32 wait_tmo;
@@ -2557,8 +2559,7 @@ lpfc_nvme_lport_unreg_wait(struct lpfc_vport *vport,
         */
        wait_tmo = msecs_to_jiffies(LPFC_NVME_WAIT_TMO * 1000);
        while (true) {
-               ret = wait_for_completion_timeout(&lport->lport_unreg_done,
-                                                 wait_tmo);
+               ret = wait_for_completion_timeout(lport_unreg_cmp, wait_tmo);
                if (unlikely(!ret)) {
                        lpfc_printf_vlog(vport, KERN_ERR, LOG_NVME_IOERR,
                                         "6176 Lport %p Localport %p wait "
@@ -2592,12 +2593,12 @@ lpfc_nvme_destroy_localport(struct lpfc_vport *vport)
        struct lpfc_nvme_lport *lport;
        struct lpfc_nvme_ctrl_stat *cstat;
        int ret;
+       DECLARE_COMPLETION_ONSTACK(lport_unreg_cmp);
 
        if (vport->nvmei_support == 0)
                return;
 
        localport = vport->localport;
-       vport->localport = NULL;
        lport = (struct lpfc_nvme_lport *)localport->private;
        cstat = lport->cstat;
 
@@ -2608,13 +2609,14 @@ lpfc_nvme_destroy_localport(struct lpfc_vport *vport)
        /* lport's rport list is clear.  Unregister
         * lport and release resources.
         */
-       init_completion(&lport->lport_unreg_done);
+       lport->lport_unreg_cmp = &lport_unreg_cmp;
        ret = nvme_fc_unregister_localport(localport);
 
        /* Wait for completion.  This either blocks
         * indefinitely or succeeds
         */
-       lpfc_nvme_lport_unreg_wait(vport, lport);
+       lpfc_nvme_lport_unreg_wait(vport, lport, &lport_unreg_cmp);
+       vport->localport = NULL;
        kfree(cstat);
 
        /* Regardless of the unregister upcall response, clear
diff --git a/drivers/scsi/lpfc/lpfc_nvme.h b/drivers/scsi/lpfc/lpfc_nvme.h
index cfd4719..b234d02 100644
--- a/drivers/scsi/lpfc/lpfc_nvme.h
+++ b/drivers/scsi/lpfc/lpfc_nvme.h
@@ -50,7 +50,7 @@ struct lpfc_nvme_ctrl_stat {
 /* Declare nvme-based local and remote port definitions. */
 struct lpfc_nvme_lport {
        struct lpfc_vport *vport;
-       struct completion lport_unreg_done;
+       struct completion *lport_unreg_cmp;
        /* Add stats counters here */
        struct lpfc_nvme_ctrl_stat *cstat;
        atomic_t fc4NvmeLsRequests;
-- 
2.1.0