From: Chris Li <chrisl@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: Kairui Song <kasong@tencent.com>, linux-mm <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Huang, Ying" <ying.huang@intel.com>,
David Hildenbrand <david@redhat.com>,
Hugh Dickins <hughd@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@suse.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 01/24] mm/swap: fix a potential undefined behavior issue
Date: Sun, 19 Nov 2023 19:35:42 -0800 [thread overview]
Message-ID: <CAF8kJuOGUQNyZesw5BY3dfwBNhL6_RG_=tXc1ZQ4VRGRtGPuMw@mail.gmail.com> (raw)
In-Reply-To: <ZVp2UE+MqkifJG4B@casper.infradead.org>
Hi Kairui,
On Sun, Nov 19, 2023 at 12:55 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Mon, Nov 20, 2023 at 03:47:17AM +0800, Kairui Song wrote:
> > From: Kairui Song <kasong@tencent.com>
> >
> > When folio is NULL, taking the address of its struct member is an
> > undefined behavior, the UB is caused by applying -> operator
I think dereferencing the NULL pointer is undefined behavior. There is
no dereferencing here. It is just pointer arithmetic of NULL pointers,
which is adding offset of page to the NULL pointer, you got NULL.
> > won't lead to a real issue, still better to fix it, also makes the
> > code less error-prone, when folio is NULL, page is also NULL,
> > instead of a meanless offset value.
I consider your reasoning is invalid. NULL pointer arithmetic should
be legal. This patch is not needed.
Chris
next prev parent reply other threads:[~2023-11-20 3:36 UTC|newest]
Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-19 19:47 [PATCH 00/24] Swapin path refactor for optimization and bugfix Kairui Song
2023-11-19 19:47 ` [PATCH 01/24] mm/swap: fix a potential undefined behavior issue Kairui Song
2023-11-19 20:55 ` Matthew Wilcox
2023-11-20 3:35 ` Chris Li [this message]
2023-11-20 11:14 ` Kairui Song
2023-11-20 17:34 ` Chris Li
2023-11-19 19:47 ` [PATCH 02/24] mm/swapfile.c: add back some comment Kairui Song
2023-11-19 19:47 ` [PATCH 03/24] mm/swap: move no readahead swapin code to a stand alone helper Kairui Song
2023-11-19 21:00 ` Matthew Wilcox
2023-11-20 11:14 ` Kairui Song
2023-11-20 14:55 ` Dan Carpenter
2023-11-21 5:34 ` Chris Li
2023-11-22 17:33 ` Kairui Song
2023-11-19 19:47 ` [PATCH 04/24] mm/swap: avoid setting page lock bit and doing extra unlock check Kairui Song
2023-11-20 4:17 ` Chris Li
2023-11-20 11:15 ` Kairui Song
2023-11-20 17:44 ` Chris Li
2023-11-22 17:32 ` Kairui Song
2023-11-22 20:57 ` Chris Li
2023-11-24 8:14 ` Kairui Song
2023-11-24 8:37 ` Christopher Li
2023-11-19 19:47 ` [PATCH 05/24] mm/swap: move readahead policy checking into swapin_readahead Kairui Song
2023-11-21 6:15 ` Chris Li
2023-11-21 6:35 ` Kairui Song
2023-11-21 7:41 ` Chris Li
2023-11-21 8:32 ` Kairui Song
2023-11-21 15:24 ` Chris Li
2023-11-19 19:47 ` [PATCH 06/24] swap: rework swapin_no_readahead arguments Kairui Song
2023-11-20 0:20 ` kernel test robot
2023-11-21 6:44 ` Chris Li
2023-11-23 10:51 ` Kairui Song
2023-11-19 19:47 ` [PATCH 07/24] mm/swap: move swap_count to header to be shared Kairui Song
2023-11-21 6:51 ` Chris Li
2023-11-21 7:03 ` Kairui Song
2023-11-19 19:47 ` [PATCH 08/24] mm/swap: check readahead policy per entry Kairui Song
2023-11-20 6:04 ` Huang, Ying
2023-11-20 11:17 ` Kairui Song
2023-11-21 1:10 ` Huang, Ying
2023-11-21 5:20 ` Chris Li
2023-11-21 5:13 ` Chris Li
2023-11-21 7:54 ` Chris Li
2023-11-23 10:52 ` Kairui Song
2023-11-19 19:47 ` [PATCH 09/24] mm/swap: inline __swap_count Kairui Song
2023-11-20 7:41 ` Huang, Ying
2023-11-21 8:02 ` Chris Li
2023-11-19 19:47 ` [PATCH 10/24] mm/swap: remove nr_rotate_swap and related code Kairui Song
2023-11-21 15:45 ` Chris Li
2023-11-19 19:47 ` [PATCH 11/24] mm/swap: also handle swapcache lookup in swapin_readahead Kairui Song
2023-11-20 0:47 ` kernel test robot
2023-11-21 16:06 ` Chris Li
2023-11-24 8:42 ` Kairui Song
2023-11-24 9:10 ` Chris Li
2023-11-19 19:47 ` [PATCH 12/24] mm/swap: simplify arguments for swap_cache_get_folio Kairui Song
2023-11-21 16:36 ` Chris Li
2023-11-19 19:47 ` [PATCH 13/24] swap: simplify swap_cache_get_folio Kairui Song
2023-11-21 16:50 ` Chris Li
2023-11-19 19:47 ` [PATCH 14/24] mm/swap: do shadow lookup as well when doing swap cache lookup Kairui Song
2023-11-21 16:55 ` Chris Li
2023-11-19 19:47 ` [PATCH 15/24] mm/swap: avoid an duplicated swap cache lookup for SYNCHRONOUS_IO device Kairui Song
2023-11-21 17:15 ` Chris Li
2023-11-22 18:08 ` Kairui Song
2023-11-19 19:47 ` [PATCH 16/24] mm/swap: reduce scope of get_swap_device in swapin path Kairui Song
2023-11-19 21:12 ` Matthew Wilcox
2023-11-20 11:14 ` Kairui Song
2023-11-21 17:25 ` Chris Li
2023-11-22 0:36 ` Huang, Ying
2023-11-23 11:13 ` Kairui Song
2023-11-24 0:40 ` Huang, Ying
2023-11-19 19:47 ` [PATCH 17/24] mm/swap: fix false error when swapoff race with swapin Kairui Song
2023-11-19 19:47 ` [PATCH 18/24] mm/swap: introduce a helper non fault swapin Kairui Song
2023-11-20 1:07 ` kernel test robot
2023-11-22 4:40 ` Chris Li
2023-11-28 11:22 ` Kairui Song
2023-12-13 2:22 ` Chris Li
2023-11-19 19:47 ` [PATCH 19/24] shmem, swap: refactor error check on OOM or race Kairui Song
2023-11-20 7:04 ` Chris Li
2023-11-20 11:17 ` Kairui Song
2023-11-19 19:47 ` [PATCH 20/24] swap: simplify and make swap_find_cache static Kairui Song
2023-11-22 5:01 ` Chris Li
2023-11-19 19:47 ` [PATCH 21/24] swap: make swapin_readahead result checking argument mandatory Kairui Song
2023-11-22 5:15 ` Chris Li
2023-11-24 8:14 ` Kairui Song
2023-11-19 19:47 ` [PATCH 22/24] swap: make swap_cluster_readahead static Kairui Song
2023-11-22 5:20 ` Chris Li
2023-11-19 19:47 ` [PATCH 23/24] swap: fix multiple swap leak when after cgroup migrate Kairui Song
2023-11-20 7:35 ` Huang, Ying
2023-11-20 11:17 ` Kairui Song
2023-11-22 5:34 ` Chris Li
2023-11-19 19:47 ` [PATCH 24/24] mm/swap: change swapin_readahead to swapin_page_fault Kairui Song
2023-11-20 19:09 ` [PATCH 00/24] Swapin path refactor for optimization and bugfix Yosry Ahmed
2023-11-20 20:22 ` Chris Li
2023-11-22 6:46 ` Kairui Song
2023-11-22 6:43 ` Kairui Song
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