Re: [PATCH] kasan: avoid overflowing quarantine size on low memory systems
From: Andrey Ryabinin <hidden>
Date: 2016-08-02 15:08:13
Also in:
lkml
On 08/01/2016 05:59 PM, Alexander Potapenko 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.
Just curious, how did find this? Overflow is possible if system has more than 32 cpus per GB of memory. AFIAK this quite unusual.
quoted hunk ↗ jump to hunk
Reported-by: Dmitry Vyukov <dvyukov@google.com> Fixes: 55834c59098d ("mm: kasan: initial memory quarantine implementation") Signed-off-by: Alexander Potapenko <glider@google.com> --- mm/kasan/quarantine.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c index 65793f1..416d3b0 100644 --- 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 +214,15 @@ 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(); + if (new_quarantine_size < percpu_quarantines) { + WARN_ONCE(1, + "Too little memory, disabling global KASAN quarantine.\n", + );
Why WARN? I'd suggest pr_warn_once();
+ new_quarantine_size = 0;
+ } else {
+ new_quarantine_size -= percpu_quarantines;
+ }
WRITE_ONCE(quarantine_size, new_quarantine_size);
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