From: Vlastimil Babka <vbabka@suse.cz>
To: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@kernel.org>
Cc: Kyungtae Kim <kt0755@gmail.com>,
pavel.tatashin@microsoft.com, osalvador@suse.de,
rppt@linux.vnet.ibm.com, aaron.lu@intel.com,
iamjoonsoo.kim@lge.com, alexander.h.duyck@linux.intel.com,
mgorman@techsingularity.net, lifeasageek@gmail.com,
threeearcat@gmail.com, syzkaller@googlegroups.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Subject: Re: UBSAN: Undefined behaviour in mm/page_alloc.c
Date: Wed, 14 Nov 2018 00:23:28 +0100 [thread overview]
Message-ID: <d88fae5c-e12d-ca35-d200-587a2ff02ec9@suse.cz> (raw)
In-Reply-To: <20181113151503.fd370e28cb9df5a0933e9b04@linux-foundation.org>
On 11/14/18 12:15 AM, Andrew Morton wrote:
> On Tue, 13 Nov 2018 10:43:05 +0100 Michal Hocko <mhocko@kernel.org> wrote:
>
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -4364,6 +4353,15 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
>> gfp_t alloc_mask; /* The gfp_t that was actually used for allocation */
>> struct alloc_context ac = { };
>>
>> + /*
>> + * There are several places where we assume that the order value is sane
>> + * so bail out early if the request is out of bound.
>> + */
>> + if (unlikely(order >= MAX_ORDER)) {
>> + WARN_ON_ONCE(!(gfp_mask & __GFP_NOWARN));
>> + return NULL;
>> + }
>> +
>
> I know "everybody enables CONFIG_DEBUG_VM", but given this is fastpath,
> we could help those who choose not to enable it by using
>
> #ifdef CONFIG_DEBUG_VM
> if (WARN_ON_ONCE(order >= MAX_ORDER && !(gfp_mask & __GFP_NOWARN)))
> return NULL;
> #endif
Hmm, but that would mean there's still potential undefined behavior for
!CONFIG_DEBUG_VM, so I would prefer not to do it like that.
>
> (Again curses 91241681c62 ("include/linux/mmdebug.h: make VM_WARN* non-rvals"))
>
next prev parent reply other threads:[~2018-11-13 23:26 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-09 4:09 UBSAN: Undefined behaviour in mm/page_alloc.c Kyungtae Kim
2018-11-09 8:42 ` Vlastimil Babka
2018-11-09 8:43 ` Michal Hocko
2018-11-09 9:41 ` Tetsuo Handa
2018-11-09 9:56 ` Michal Hocko
2018-11-09 10:07 ` Tetsuo Handa
2018-11-09 10:25 ` Michal Hocko
2018-11-09 10:10 ` Vlastimil Babka
2018-11-09 10:22 ` Michal Hocko
2018-11-09 10:24 ` Tetsuo Handa
2018-11-09 10:28 ` Michal Hocko
2018-11-09 10:52 ` Balbir Singh
2018-11-09 9:56 ` Mel Gorman
2018-11-13 9:43 ` Michal Hocko
2018-11-13 23:15 ` Andrew Morton
2018-11-13 23:23 ` Vlastimil Babka [this message]
2018-11-13 23:32 ` Andrew Morton
2018-11-14 0:05 ` Vlastimil Babka
2018-11-19 23:57 ` Pavel Machek
2018-11-13 23:29 ` Andrew Morton
2018-11-14 7:10 ` Michal Hocko
2018-11-16 23:43 ` Dmitry Vyukov
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