Re: [PATCH] kasan: avoid overflowing quarantine size on low memory systems
From: <hidden>
Date: 2016-08-31 04:16:04
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On Monday, August 1, 2016 at 10:59:29 AM UTC-4, Alexander Potapenko 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. 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", + ); + new_quarantine_size = 0; + } else { + new_quarantine_size -= percpu_quarantines; + } WRITE_ONCE(quarantine_size, new_quarantine_size); last = global_quarantine.head;-- 2.8.0.rc3.226.g39d4020
On Monday, August 1, 2016 at 10:59:29 AM UTC-4, Alexander Potapenko 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. 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", + ); + new_quarantine_size = 0; + } else { + new_quarantine_size -= percpu_quarantines; + } WRITE_ONCE(quarantine_size, new_quarantine_size); last = global_quarantine.head;-- 2.8.0.rc3.226.g39d4020