Re: [PATCH] kasan: avoid overflowing quarantine size on low memory systems
From: Andrew Morton <akpm@linux-foundation.org>
Date: 2016-08-01 20:41:59
Also in:
lkml
On Mon, 1 Aug 2016 16:59:23 +0200 Alexander Potapenko [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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@@ -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", + ); + new_quarantine_size = 0; + } else { + new_quarantine_size -= percpu_quarantines; + } WRITE_ONCE(quarantine_size, new_quarantine_size); last = global_quarantine.head;
This is a little tidier:
--- a/mm/kasan/quarantine.c~kasan-avoid-overflowing-quarantine-size-on-low-memory-systems-fix
+++ a/mm/kasan/quarantine.c@@ -217,14 +217,11 @@ void quarantine_reduce(void) new_quarantine_size = (READ_ONCE(totalram_pages) << PAGE_SHIFT) / QUARANTINE_FRACTION; 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", - ); + if (WARN_ONCE(new_quarantine_size < percpu_quarantines, + "Too little memory, disabling global KASAN quarantine.\n")) new_quarantine_size = 0; - } else { + else new_quarantine_size -= percpu_quarantines; - } WRITE_ONCE(quarantine_size, new_quarantine_size); last = global_quarantine.head;
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