Re: [Qemu-block] [Qemu-devel] [PATCH] block/pflash_cfi02: Fix memory leak and potential use-after-free

[Wei Yang]

On Tue, Feb 19, 2019 at 10:37:27AM -0500, Stephen Checkoway wrote:
>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 

Reviewed-by: Wei Yang 

>---
> hw/block/pflash_cfi02.c | 15 +++
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
>diff --git a/hw/block/pflash_cfi02.c b/hw/block/pflash_cfi02.c
>index 0f8b7b8c7b..1588aeff5a 100644
>--- a/hw/block/pflash_cfi02.c
>+++ b/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(>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(>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), >mem);
> 
>-pfl->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, pflash_timer, pfl);
>+timer_init_ns(>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(>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);
> }
>-- 
>2.17.2 (Apple Git-113)
>

-- 
Wei Yang
Help you, Help me

Re: [Qemu-block] [Qemu-devel] [PATCH] block/pflash_cfi02: Fix memory leak and potential use-after-free

[Philippe Mathieu-Daudé]

On 2/19/19 4:37 PM, Stephen Checkoway wrote:
> 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 
> ---
>  hw/block/pflash_cfi02.c | 15 +++
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/block/pflash_cfi02.c b/hw/block/pflash_cfi02.c
> index 0f8b7b8c7b..1588aeff5a 100644
> --- a/hw/block/pflash_cfi02.c
> +++ b/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(>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(>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), >mem);
>  
> -pfl->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, pflash_timer, pfl);
> +timer_init_ns(>timer, QEMU_CLOCK_VIRTUAL, pflash_timer, pfl);

Reviewed-by: Philippe Mathieu-Daudé 

>  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(>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);
>  }
>