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SubjectRe: [PATCH v2] kasan: avoid overflowing quarantine size on low memory systems
On Tue,  2 Aug 2016 12:27:00 +0200 Alexander Potapenko <glider@google.com> wrote:

> If the total amount of memory assigned to quarantine is less than the
> amount of memory assigned to per-cpu quarantines, |new_quarantine_size|
> may overflow. Instead, set it to zero.
>
> ...
>
> --- a/mm/kasan/quarantine.c
> +++ b/mm/kasan/quarantine.c
> @@ -196,7 +196,7 @@ void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache)
>
> void quarantine_reduce(void)
> {
> - size_t new_quarantine_size;
> + size_t new_quarantine_size, percpu_quarantines;
> unsigned long flags;
> struct qlist_head to_free = QLIST_INIT;
> size_t size_to_free = 0;
> @@ -214,7 +214,9 @@ void quarantine_reduce(void)
> */
> new_quarantine_size = (READ_ONCE(totalram_pages) << PAGE_SHIFT) /
> QUARANTINE_FRACTION;
> - new_quarantine_size -= QUARANTINE_PERCPU_SIZE * num_online_cpus();
> + percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus();
> + new_quarantine_size = (new_quarantine_size < percpu_quarantines) ?
> + 0 : new_quarantine_size - percpu_quarantines;
> WRITE_ONCE(quarantine_size, new_quarantine_size);
>
> last = global_quarantine.head;

Confused. Which kernel version is this supposed to apply to?

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