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Subject[PATCH] user_events: Use alloc_pages instead of kzalloc for register pages
Date
kzalloc virtual addresses do not work with SetPageReserved, use the
actual page virtual addresses instead via alloc_pages.

The issue is reported when booting with user_events and
DEBUG_VM_PGFLAGS=y.

Link: https://lore.kernel.org/linux-trace-devel/CADYN=9+xY5Vku3Ws5E9S60SM5dCFfeGeRBkmDFbcxX0ZMoFing@mail.gmail.com/#R

Reported-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
---
kernel/trace/trace_events_user.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 2b5e9fdb63a0..59c900789757 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -1587,16 +1587,20 @@ static void set_page_reservations(bool set)
static int __init trace_events_user_init(void)
{
int ret;
+ struct page *register_pages;

/* Zero all bits beside 0 (which is reserved for failures) */
bitmap_zero(page_bitmap, MAX_EVENTS);
set_bit(0, page_bitmap);

- register_page_data = kzalloc(MAX_EVENTS, GFP_KERNEL);
+ register_pages = alloc_pages(GFP_KERNEL | __GFP_ZERO,
+ get_order(MAX_EVENTS));

- if (!register_page_data)
+ if (!register_pages)
return -ENOMEM;

+ register_page_data = page_address(register_pages);
+
set_page_reservations(true);

ret = create_user_tracefs();
@@ -1604,7 +1608,7 @@ static int __init trace_events_user_init(void)
if (ret) {
pr_warn("user_events could not register with tracefs\n");
set_page_reservations(false);
- kfree(register_page_data);
+ __free_pages(register_pages, get_order(MAX_EVENTS));
return ret;
}

base-commit: 864ea0e10cc90416a01b46f0d47a6f26dc020820
--
2.17.1

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