block/pflash_cfi02: Fix memory leak and potential use-after-free

Don't dynamically allocate the pflash's timer. But do use timer_del in
an unrealize function to make sure that the timer can't fire after the
pflash_t has been freed.

Signed-off-by: Stephen Checkoway <stephen.checkoway@oberlin.edu>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Wei Yang <richardw.yang@linux.intel.com>
Message-Id: <20190219153727.62279-1-stephen.checkoway@oberlin.edu>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
(cherry picked from commit d80cf1e)
*prereq for 1643406/3a283507
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

hw/block/pflash_cfi02.c

@@ -84,7 +84,7 @@ struct pflash_t {
     uint16_t unlock_addr0;
     uint16_t unlock_addr1;
     uint8_t cfi_table[0x52];
-    QEMUTimer *timer;
+    QEMUTimer timer;
     /* The device replicates the flash memory across its memory space.  Emulate
      * that by having a container (.mem) filled with an array of aliases
      * (.mem_mappings) pointing to the flash memory (.orig_mem).
@@ -429,7 +429,7 @@ static void pflash_write (pflash_t *pfl, hwaddr offset,
             }
             pfl->status = 0x00;
             /* Let's wait 5 seconds before chip erase is done */
-            timer_mod(pfl->timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
+            timer_mod(&pfl->timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
                       (NANOSECONDS_PER_SECOND * 5));
             break;
         case 0x30:
@@ -444,7 +444,7 @@ static void pflash_write (pflash_t *pfl, hwaddr offset,
             }
             pfl->status = 0x00;
             /* Let's wait 1/2 second before sector erase is done */
-            timer_mod(pfl->timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
+            timer_mod(&pfl->timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
                       (NANOSECONDS_PER_SECOND / 2));
             break;
         default:
@@ -596,7 +596,7 @@ static void pflash_cfi02_realize(DeviceState *dev, Error **errp)
     pfl->rom_mode = 1;
     sysbus_init_mmio(SYS_BUS_DEVICE(dev), &pfl->mem);
 
-    pfl->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, pflash_timer, pfl);
+    timer_init_ns(&pfl->timer, QEMU_CLOCK_VIRTUAL, pflash_timer, pfl);
     pfl->wcycle = 0;
     pfl->cmd = 0;
     pfl->status = 0;
@@ -695,11 +695,18 @@ static Property pflash_cfi02_properties[] = {
     DEFINE_PROP_END_OF_LIST(),
 };
 
+static void pflash_cfi02_unrealize(DeviceState *dev, Error **errp)
+{
+    pflash_t *pfl = CFI_PFLASH02(dev);
+    timer_del(&pfl->timer);
+}
+
 static void pflash_cfi02_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
 
     dc->realize = pflash_cfi02_realize;
+    dc->unrealize = pflash_cfi02_unrealize;
     dc->props = pflash_cfi02_properties;
     set_bit(DEVICE_CATEGORY_STORAGE, dc->categories);
 }