On 2023/7/10 20:00, Peter Zijlstra wrote: > On Tue, Jun 13, 2023 at 08:32:11PM +0800, Shuai Xue wrote: > >> kernel/events/ring_buffer.c | 13 +++++++++++++ >> tools/perf/Documentation/perf-record.txt | 3 ++- >> 2 files changed, 15 insertions(+), 1 deletion(-) >> >> diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c >> index a0433f37b024..e514aaba9d42 100644 >> --- a/kernel/events/ring_buffer.c >> +++ b/kernel/events/ring_buffer.c >> @@ -673,6 +673,7 @@ int rb_alloc_aux(struct perf_buffer *rb, struct perf_event *event, >> bool overwrite = !(flags & RING_BUFFER_WRITABLE); >> int node = (event->cpu == -1) ? -1 : cpu_to_node(event->cpu); >> int ret = -ENOMEM, max_order; >> + size_t bytes; >> >> if (!has_aux(event)) >> return -EOPNOTSUPP; >> @@ -699,6 +700,18 @@ int rb_alloc_aux(struct perf_buffer *rb, struct perf_event *event, >> watermark = 0; >> } >> >> + /* >> + * 'rb->aux_pages' allocated by kcalloc() is a pointer array which is >> + * used to maintains AUX trace pages. The allocated page for this array >> + * is physically contiguous (and virtually contiguous) with an order of >> + * 0..MAX_ORDER. If the size of pointer array crosses the limitation set >> + * by MAX_ORDER, it reveals a WARNING. >> + * >> + * So bail out early if the request AUX area is out of bound. >> + */ >> + if (check_mul_overflow(nr_pages, sizeof(void *), &bytes) || >> + get_order(bytes) > MAX_ORDER) >> + return -EINVAL; > > This is all quite horrific :/ What's wrong with something simple: > > /* Can't allocate more than MAX_ORDER */ > if (get_order((unsigned long)nr_pages * sizeof(void*)) > MAX_ORDER) > return -EINVAL; > > If you're on 32bit then nr_pages should never be big enough to overflow, > fundamentally you'll only have 32-PAGE_SHIFT bits in nr_pages. Well, you are right. Thank you for pointing it out. I will send a new version with your simplified code :) Best Regards, Shuai > > >> rb->aux_pages = kcalloc_node(nr_pages, sizeof(void *), GFP_KERNEL, >> node); >
