[PATCH v2 18/51] hw/nvme: fix aio cancel in flush

[Juan Quintela]

From: Klaus Jensen <k.jensen@samsung.com>

Make sure that iocb->aiocb is NULL'ed when cancelling.

Fix a potential use-after-free by removing the bottom half and enqueuing
the completion directly.

Fixes: 38f4ac65ac88 ("hw/nvme: reimplement flush to allow cancellation")
Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
---
 hw/nvme/ctrl.c | 21 ++++++---------------
 1 file changed, 6 insertions(+), 15 deletions(-)

diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
index 9bc56075f6..fede5af6af 100644
--- a/hw/nvme/ctrl.c
+++ b/hw/nvme/ctrl.c
@@ -3160,7 +3160,6 @@ typedef struct NvmeFlushAIOCB {
     BlockAIOCB common;
     BlockAIOCB *aiocb;
     NvmeRequest *req;
-    QEMUBH *bh;
     int ret;
 
     NvmeNamespace *ns;
@@ -3176,6 +3175,7 @@ static void nvme_flush_cancel(BlockAIOCB *acb)
 
     if (iocb->aiocb) {
         blk_aio_cancel_async(iocb->aiocb);
+        iocb->aiocb = NULL;
     }
 }
 
@@ -3185,6 +3185,8 @@ static const AIOCBInfo nvme_flush_aiocb_info = {
     .get_aio_context = nvme_get_aio_context,
 };
 
+static void nvme_do_flush(NvmeFlushAIOCB *iocb);
+
 static void nvme_flush_ns_cb(void *opaque, int ret)
 {
     NvmeFlushAIOCB *iocb = opaque;
@@ -3206,13 +3208,11 @@ static void nvme_flush_ns_cb(void *opaque, int ret)
     }
 
 out:
-    iocb->aiocb = NULL;
-    qemu_bh_schedule(iocb->bh);
+    nvme_do_flush(iocb);
 }
 
-static void nvme_flush_bh(void *opaque)
+static void nvme_do_flush(NvmeFlushAIOCB *iocb)
 {
-    NvmeFlushAIOCB *iocb = opaque;
     NvmeRequest *req = iocb->req;
     NvmeCtrl *n = nvme_ctrl(req);
     int i;
@@ -3239,14 +3239,8 @@ static void nvme_flush_bh(void *opaque)
     return;
 
 done:
-    qemu_bh_delete(iocb->bh);
-    iocb->bh = NULL;
-
     iocb->common.cb(iocb->common.opaque, iocb->ret);
-
     qemu_aio_unref(iocb);
-
-    return;
 }
 
 static uint16_t nvme_flush(NvmeCtrl *n, NvmeRequest *req)
@@ -3258,7 +3252,6 @@ static uint16_t nvme_flush(NvmeCtrl *n, NvmeRequest *req)
     iocb = qemu_aio_get(&nvme_flush_aiocb_info, NULL, nvme_misc_cb, req);
 
     iocb->req = req;
-    iocb->bh = qemu_bh_new(nvme_flush_bh, iocb);
     iocb->ret = 0;
     iocb->ns = NULL;
     iocb->nsid = 0;
@@ -3280,13 +3273,11 @@ static uint16_t nvme_flush(NvmeCtrl *n, NvmeRequest 
*req)
     }
 
     req->aiocb = &iocb->common;
-    qemu_bh_schedule(iocb->bh);
+    nvme_do_flush(iocb);
 
     return NVME_NO_COMPLETE;
 
 out:
-    qemu_bh_delete(iocb->bh);
-    iocb->bh = NULL;
     qemu_aio_unref(iocb);
 
     return status;
-- 
2.38.1