From 222b22e1f32d7f96d5a4fdb15f3be3eb82cf340c Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Wed, 13 Feb 2019 07:57:02 +0100 Subject: perf/core: Fix impossible ring-buffer sizes warning commit 528871b456026e6127d95b1b2bd8e3a003dc1614 upstream. The following commit: 9dff0aa95a32 ("perf/core: Don't WARN() for impossible ring-buffer sizes") results in perf recording failures with larger mmap areas: root@skl:/tmp# perf record -g -a failed to mmap with 12 (Cannot allocate memory) The root cause is that the following condition is buggy: if (order_base_2(size) >= MAX_ORDER) goto fail; The problem is that @size is in bytes and MAX_ORDER is in pages, so the right test is: if (order_base_2(size) >= PAGE_SHIFT+MAX_ORDER) goto fail; Fix it. Reported-by: "Jin, Yao" Bisected-by: Borislav Petkov Analyzed-by: Peter Zijlstra Cc: Julien Thierry Cc: Mark Rutland Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Greg Kroah-Hartman Cc: Fixes: 9dff0aa95a32 ("perf/core: Don't WARN() for impossible ring-buffer sizes") Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- kernel/events/ring_buffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 93bfb61506fa..358bb53c1e74 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -637,7 +637,7 @@ struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags) size = sizeof(struct ring_buffer); size += nr_pages * sizeof(void *); - if (order_base_2(size) >= MAX_ORDER) + if (order_base_2(size) >= PAGE_SHIFT+MAX_ORDER) goto fail; rb = kzalloc(size, GFP_KERNEL); -- cgit v1.2.3