Commit c3cee372 authored by Alexander Potapenko's avatar Alexander Potapenko Committed by Linus Torvalds

kasan: avoid overflowing quarantine size on low memory systems

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.

[akpm@linux-foundation.org: cleanup: use WARN_ONCE return value]
Link: http://lkml.kernel.org/r/1470063563-96266-1-git-send-email-glider@google.com
Fixes: 55834c59 ("mm: kasan: initial memory quarantine implementation")
Signed-off-by: default avatarAlexander Potapenko <glider@google.com>
Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7e088978
......@@ -198,7 +198,7 @@ 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;
......@@ -216,7 +216,12 @@ 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 (WARN_ONCE(new_quarantine_size < percpu_quarantines,
"Too little memory, disabling global KASAN quarantine.\n"))
new_quarantine_size = 0;
else
new_quarantine_size -= percpu_quarantines;
WRITE_ONCE(quarantine_size, new_quarantine_size);
last = global_quarantine.head;
......
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