AppArmor: Use GFP_KERNEL for __aa_kvmalloc().

Calling kmalloc(GFP_NOIO) with order == PAGE_ALLOC_COSTLY_ORDER is not
recommended because it might fall into infinite retry loop without
invoking the OOM killer.

Since aa_dfa_unpack() is the only caller of kvzalloc() and
aa_dfa_unpack() which is calling kvzalloc() via unpack_table() is
doing kzalloc(GFP_KERNEL), it is safe to use GFP_KERNEL from
__aa_kvmalloc().

Since aa_simple_write_to_buffer() is the only caller of kvmalloc()
and aa_simple_write_to_buffer() is calling copy_from_user() which
is GFP_KERNEL context (see memdup_user_nul()), it is safe to use
GFP_KERNEL from __aa_kvmalloc().

Therefore, replace GFP_NOIO with GFP_KERNEL. Also, since we have
vmalloc() fallback, add __GFP_NORETRY so that we don't invoke the OOM
killer by kmalloc(GFP_KERNEL) with order == PAGE_ALLOC_COSTLY_ORDER.
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: John Johansen <john.johansen@canonical.com>

security/apparmor/lib.c

@@ -95,7 +95,8 @@ void *__aa_kvmalloc(size_t size, gfp_t flags)
 
 	/* do not attempt kmalloc if we need more than 16 pages at once */
 	if (size <= (16*PAGE_SIZE))
-		buffer = kmalloc(size, flags | GFP_NOIO | __GFP_NOWARN);
+		buffer = kmalloc(size, flags | GFP_KERNEL | __GFP_NORETRY |
+				 __GFP_NOWARN);
 	if (!buffer) {
 		if (flags & __GFP_ZERO)
 			buffer = vzalloc(size);