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.

Link: http://lkml.kernel.org/r/20190220204058.11676-1-daniel.vetter@ffwll.chSigned-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Stancek <jstancek@redhat.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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);