blockdev: Fix drive_add for drives without media

Watch this:

    (qemu) drive_add 0 if=none
    (qemu) info block
    none0: type=hd removable=0 [not inserted]
    (qemu) drive_del none0
    Segmentation fault (core dumped)

add_init_drive() is confused about drive_init()'s failure modes, and
cleans up when it shouldn't.  This leaves the DriveInfo with member
opts dangling.  drive_del attempts to free it, and dies.

drive_init() behaves as follows:

* If it created a drive with media, it returns its DriveInfo.

* If it created a drive without media, it clears *fatal_error and
  returns NULL.

* If it couldn't create a drive, it sets *fatal_error and returns
  NULL.

Of its three callers:

* drive_init_func() is correct.

* usb_msd_init() assumes drive_init() failed when it returns NULL.
  This is correct only because it always passes option "file", and
  "drive without media" can't happen then.

* add_init_drive() assumes drive_init() failed when it returns NULL.
  This is incorrect.

Clean up drive_init() to return NULL on failure and only on failure.
Drop its parameter fatal_error.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 2 insertions, 6 deletions

diff --git a/blockdev.c b/blockdev.c
index 4b2145c25b..1c56da0a16 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -203,7 +203,7 @@ static int parse_block_error_action(const char *buf, int is_read)
     }
 }
 
-DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi, int *fatal_error)
+DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi)
 {
     const char *buf;
     const char *file = NULL;
@@ -225,8 +225,6 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi, int *fatal_error)
     int snapshot = 0;
     int ret;
 
-    *fatal_error = 1;
-
     translation = BIOS_ATA_TRANSLATION_AUTO;
 
     if (default_to_scsi) {
@@ -499,8 +497,7 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi, int *fatal_error)
         abort();
     }
     if (!file || !*file) {
-        *fatal_error = 0;
-        return NULL;
+        return dinfo;
     }
     if (snapshot) {
         /* always use cache=unsafe with snapshot */
@@ -529,7 +526,6 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi, int *fatal_error)
 
     if (bdrv_key_required(dinfo->bdrv))
         autostart = 0;
-    *fatal_error = 0;
     return dinfo;
 }