4.20-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ingo Molnar <mingo@xxxxxxxxxx>
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" <yao.jin@xxxxxxxxxxxxxxx>
Bisected-by: Borislav Petkov <bp@xxxxxxxxx>
Analyzed-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Julien Thierry <julien.thierry@xxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 9dff0aa95a32 ("perf/core: Don't WARN() for impossible ring-buffer sizes")
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/events/ring_buffer.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -734,7 +734,7 @@ struct ring_buffer *rb_alloc(int nr_page
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);
