linux-kernel - [PATCH] mm: Don't let userspace spam allocations warnings

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Date:   Wed, 20 Feb 2019 21:40:58 +0100
From:   Daniel Vetter <daniel.vetter@...ll.ch>
To:     DRI Development <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Michal Hocko <mhocko@...e.com>, Roman Gushchin <guro@...com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Jan Stancek <jstancek@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Huang Ying <ying.huang@...el.com>,
        Bartosz Golaszewski <brgl@...ev.pl>, linux-mm@...ck.org
Subject: [PATCH] mm: Don't let userspace spam allocations warnings

memdump_user usually gets fed unchecked userspace input. Blasting a
full backtrace into dmesg every time is a bit excessive - I'm not sure
on the kernel rule in general, but at least in drm we're trying not to
let unpriviledge userspace spam the logs freely. Definitely not entire
warning backtraces.

It also means more filtering for our CI, because our testsuite
exercises these corner cases and so hits these a lot.

Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Mike Rapoport <rppt@...ux.vnet.ibm.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Roman Gushchin <guro@...com>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Jan Stancek <jstancek@...hat.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc: "Michael S. Tsirkin" <mst@...hat.com>
Cc: Huang Ying <ying.huang@...el.com>
Cc: Bartosz Golaszewski <brgl@...ev.pl>
Cc: linux-mm@...ck.org
---
 mm/util.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/util.c b/mm/util.c
index 1ea055138043..379319b1bcfd 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -150,7 +150,7 @@ void *memdup_user(const void __user *src, size_t len)
 {
 	void *p;
 
-	p = kmalloc_track_caller(len, GFP_USER);
+	p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN);
 	if (!p)
 		return ERR_PTR(-ENOMEM);
 
-- 
2.20.1