git: 6f5141456ed0 - main - vtblk: secondary fix for dumping

[Mitchell Horne]

The branch main has been updated by mhorne:

URL: 
https://cgit.FreeBSD.org/src/commit/?id=6f5141456ed07a24097c2cf3d6c389bf971d78d2

commit 6f5141456ed07a24097c2cf3d6c389bf971d78d2
Author:     Mitchell Horne <mho...@freebsd.org>
AuthorDate: 2023-01-09 17:14:19 +0000
Commit:     Mitchell Horne <mho...@freebsd.org>
CommitDate: 2023-01-23 19:21:36 +0000

    vtblk: secondary fix for dumping
    
    The code paths while dumping do not got through busdma. As such,
    safeguard against calling bus_dmamap_sync() with a NULL map. The x86
    implementation tolerates this but others do not, resulting in a
    NULL dereference panic when dumping to a vtblk device on arm64, riscv,
    etc.
    
    Fixes:          782105f7c898 ("vtblk: Use busdma")
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D37990
---
 sys/dev/virtio/block/virtio_blk.c | 46 ++++++++++++++++++++++-----------------
 1 file changed, 26 insertions(+), 20 deletions(-)

diff --git a/sys/dev/virtio/block/virtio_blk.c 
b/sys/dev/virtio/block/virtio_blk.c
index 052017251c22..0e66cd3c89db 100644
--- a/sys/dev/virtio/block/virtio_blk.c
+++ b/sys/dev/virtio/block/virtio_blk.c
@@ -1126,15 +1126,17 @@ vtblk_request_execute_cb(void * callback_arg, 
bus_dma_segment_t * segs,
        sglist_append(sg, &req->vbr_ack, sizeof(uint8_t));
        readable = sg->sg_nseg - writable;
 
-       switch (bp->bio_cmd) {
-       case BIO_READ:
-               bus_dmamap_sync(sc->vtblk_dmat, req->vbr_mapp,
-                   BUS_DMASYNC_PREREAD);
-               break;
-       case BIO_WRITE:
-               bus_dmamap_sync(sc->vtblk_dmat, req->vbr_mapp,
-                   BUS_DMASYNC_PREWRITE);
-               break;
+       if (req->vbr_mapp != NULL) {
+               switch (bp->bio_cmd) {
+               case BIO_READ:
+                       bus_dmamap_sync(sc->vtblk_dmat, req->vbr_mapp,
+                           BUS_DMASYNC_PREREAD);
+                       break;
+               case BIO_WRITE:
+                       bus_dmamap_sync(sc->vtblk_dmat, req->vbr_mapp,
+                           BUS_DMASYNC_PREWRITE);
+                       break;
+               }
        }
 
        error = virtqueue_enqueue(vq, req, sg, readable, writable);
@@ -1191,17 +1193,21 @@ vtblk_queue_completed(struct vtblk_softc *sc, struct 
bio_queue *queue)
                }
 
                bp = req->vbr_bp;
-               switch (bp->bio_cmd) {
-               case BIO_READ:
-                       bus_dmamap_sync(sc->vtblk_dmat, req->vbr_mapp,
-                           BUS_DMASYNC_POSTREAD);
-                       bus_dmamap_unload(sc->vtblk_dmat, req->vbr_mapp);
-                       break;
-               case BIO_WRITE:
-                       bus_dmamap_sync(sc->vtblk_dmat, req->vbr_mapp,
-                           BUS_DMASYNC_POSTWRITE);
-                       bus_dmamap_unload(sc->vtblk_dmat, req->vbr_mapp);
-                       break;
+               if (req->vbr_mapp != NULL) {
+                       switch (bp->bio_cmd) {
+                       case BIO_READ:
+                               bus_dmamap_sync(sc->vtblk_dmat, req->vbr_mapp,
+                                   BUS_DMASYNC_POSTREAD);
+                               bus_dmamap_unload(sc->vtblk_dmat,
+                                   req->vbr_mapp);
+                               break;
+                       case BIO_WRITE:
+                               bus_dmamap_sync(sc->vtblk_dmat, req->vbr_mapp,
+                                   BUS_DMASYNC_POSTWRITE);
+                               bus_dmamap_unload(sc->vtblk_dmat,
+                                   req->vbr_mapp);
+                               break;
+                       }
                }
                bp->bio_error = vtblk_request_error(req);
                TAILQ_INSERT_TAIL(queue, bp, bio_queue);