[Qemu-devel] [PATCH] scsi-cd: Fix crash after remote cdrom detached

[Xiang Zheng]

There is a small window between the twice blk_is_available in
scsi_disk_emulate_command which would cause crash due to the later
assertion if the remote cdrom is detached in this window.

So this patch replaces assertions with return to avoid qemu crash.

Signed-off-by: Xiang Zheng <address@hidden>
---
The qemu error log shows:

qemu-system-aarch64: /home/qemu/hw/scsi/scsi-disk.c:1896: 
scsi_disk_emulate_command: Assertion `blk_is_available(s->qdev.conf.blk)' 
failed.
2019-02-15 04:35:18.592: shutting down, reason=crashed

---
 hw/scsi/scsi-disk.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index d4e83ae..6bcafe2 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -1890,7 +1890,10 @@ static int32_t scsi_disk_emulate_command(SCSIRequest 
*req, uint8_t *buf)
     memset(outbuf, 0, r->buflen);
     switch (req->cmd.buf[0]) {
     case TEST_UNIT_READY:
-        assert(blk_is_available(s->qdev.conf.blk));
+        if (!blk_is_available(s->qdev.conf.blk)) {
+            scsi_check_condition(r, SENSE_CODE(NO_MEDIUM));
+            return 0;
+        }
         break;
     case INQUIRY:
         buflen = scsi_disk_emulate_inquiry(req, outbuf);
-- 
1.8.3.1