[Xen-devel] Ping: [PATCH v2] timers: limit heap size

[Jan Beulich <JBeulich@xxxxxxxx>]

>>> On 05.06.19 at 08:51,  wrote:
> First and foremost make timer_softirq_action() avoid growing the heap
> if its new size can't be stored without truncation. 64k entries is a
> lot, and I don't think we're at risk of actually running into the issue,
> but I also think it's better not to allow for hard to debug problems to
> occur in the first place.
> 
> Furthermore also adjust the code such the size/limit fields becoming
> unsigned int would at least work from a mere sizing point of view. For
> this also switch various uses of plain int to unsigned int.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> v2: Log (once) when heap limit would have been exceeded.
> 
> --- a/xen/common/timer.c
> +++ b/xen/common/timer.c
> @@ -63,9 +63,9 @@ static struct heap_metadata *heap_metada
>  }
>  
>  /* Sink down element @pos of @heap. */
> -static void down_heap(struct timer **heap, int pos)
> +static void down_heap(struct timer **heap, unsigned int pos)
>  {
> -    int sz = heap_metadata(heap)->size, nxt;
> +    unsigned int sz = heap_metadata(heap)->size, nxt;
>      struct timer *t = heap[pos];
>  
>      while ( (nxt = (pos << 1)) <= sz )
> @@ -84,7 +84,7 @@ static void down_heap(struct timer **hea
>  }
>  
>  /* Float element @pos up @heap. */
> -static void up_heap(struct timer **heap, int pos)
> +static void up_heap(struct timer **heap, unsigned int pos)
>  {
>      struct timer *t = heap[pos];
>  
> @@ -103,8 +103,8 @@ static void up_heap(struct timer **heap,
>  /* Delete @t from @heap. Return TRUE if new top of heap. */
>  static int remove_from_heap(struct timer **heap, struct timer *t)
>  {
> -    int sz = heap_metadata(heap)->size;
> -    int pos = t->heap_offset;
> +    unsigned int sz = heap_metadata(heap)->size;
> +    unsigned int pos = t->heap_offset;
>  
>      if ( unlikely(pos == sz) )
>      {
> @@ -130,7 +130,7 @@ static int remove_from_heap(struct timer
>  /* Add new entry @t to @heap. Return TRUE if new top of heap. */
>  static int add_to_heap(struct timer **heap, struct timer *t)
>  {
> -    int sz = heap_metadata(heap)->size;
> +    unsigned int sz = heap_metadata(heap)->size;
>  
>      /* Fail if the heap is full. */
>      if ( unlikely(sz == heap_metadata(heap)->limit) )
> @@ -463,9 +463,17 @@ static void timer_softirq_action(void)
>      if ( unlikely(ts->list != NULL) )
>      {
>          /* old_limit == (2^n)-1; new_limit == (2^(n+4))-1 */
> -        int old_limit = heap_metadata(heap)->limit;
> -        int new_limit = ((old_limit + 1) << 4) - 1;
> -        struct timer **newheap = xmalloc_array(struct timer *, new_limit + 
> 1);
> +        unsigned int old_limit = heap_metadata(heap)->limit;
> +        unsigned int new_limit = ((old_limit + 1) << 4) - 1;
> +        struct timer **newheap = NULL;
> +
> +        /* Don't grow the heap beyond what is representable in its 
> metadata. */
> +        if ( new_limit == (typeof(heap_metadata(heap)->limit))new_limit &&
> +             new_limit + 1 )
> +            newheap = xmalloc_array(struct timer *, new_limit + 1);
> +        else
> +            printk_once(XENLOG_WARNING "CPU%u: timer heap limit reached\n",
> +                        smp_processor_id());
>          if ( newheap != NULL )
>          {
>              spin_lock_irq(&ts->lock);
> @@ -544,7 +549,7 @@ static void dump_timerq(unsigned char ke
>      struct timers *ts;
>      unsigned long  flags;
>      s_time_t       now = NOW();
> -    int            i, j;
> +    unsigned int   i, j;
>  
>      printk("Dumping timer queues:\n");
>  
> @@ -556,7 +561,7 @@ static void dump_timerq(unsigned char ke
>          spin_lock_irqsave(&ts->lock, flags);
>          for ( j = 1; j <= heap_metadata(ts->heap)->size; j++ )
>              dump_timer(ts->heap[j], now);
> -        for ( t = ts->list, j = 0; t != NULL; t = t->list_next, j++ )
> +        for ( t = ts->list; t != NULL; t = t->list_next )
>              dump_timer(t, now);
>          spin_unlock_irqrestore(&ts->lock, flags);
>      }
> 
> 
> 
> 
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel