4.7-stable review patch. If anyone has any objections, please let me know.
------------------ From: Alexander Potapenko <[email protected]> commit c3cee372282cb6bcdf19ac1457581d5dd5ecb554 upstream. 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. [[email protected]: cleanup: use WARN_ONCE return value] Link: http://lkml.kernel.org/r/[email protected] Fixes: 55834c59098d ("mm: kasan: initial memory quarantine implementation") Signed-off-by: Alexander Potapenko <[email protected]> Reported-by: Dmitry Vyukov <[email protected]> Cc: Andrey Ryabinin <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- mm/kasan/quarantine.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) --- a/mm/kasan/quarantine.c +++ b/mm/kasan/quarantine.c @@ -196,7 +196,7 @@ void quarantine_put(struct kasan_free_me 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 +214,12 @@ 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;
