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b=MS8uxI9tVsBgWSxJnntJydZYFQUQRYXC1WVZESGMXFMpfLJ9kWzZanXanp5F24u4U 46bggIW0yFZPfhymOcEmbxf5hQw44F/GldAe0aN9PRwbvhWWni/585TjhxIsFWhb/q AccmqfCVCcUqWmmJioOaPcKQWLg4eAxEVq5W9MHAxU4ZkDqIw8rWRQM5GHY9hE0Egh JoBuEiV8Tscb1fOVnof4rS6DdRcgbL7sHOkYR+iI94nEY696sd0ZsV/J0/pA0p1THN oF/4gbTwrmte+i8+VX72e7fzcklktB6dQ6bE8Wy6CyaFxNyogYdcdz5efjqligZYLI qzXk5Pys8Zi2w== From: Pratyush Yadav To: Andrew Morton Cc: Pratyush Yadav , Chenghao Duan , pasha.tatashin@soleen.com, rppt@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, jianghaoran@kylinos.cn Subject: Re: [PATCH v3 7/7] mm/memfd_luo: fix integer overflow in memfd_luo_preserve_folios In-Reply-To: <20260402105845.f4d375734c0b21a1203fb9c0@linux-foundation.org> (Andrew Morton's message of "Thu, 2 Apr 2026 10:58:45 -0700") References: <20260326084727.118437-1-duanchenghao@kylinos.cn> <20260326084727.118437-8-duanchenghao@kylinos.cn> <2vxzv7e9ftwd.fsf@kernel.org> <20260402105845.f4d375734c0b21a1203fb9c0@linux-foundation.org> Date: Fri, 03 Apr 2026 09:06:46 +0000 Message-ID: <2vxzqzowe7kp.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Queue-Id: C3D7B180002 X-Stat-Signature: 4d97ydbzb7uirnoo97hd79rcg7qtozqk X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1775207211-555486 X-HE-Meta: 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 nR2wEmkW 6OP8wiv7115kQl2MbqM/Kr1vxbrBUUfldhWdOVCksgSXMVy3TIh1CJEL5a0/pXSRL5KlVr6PtBgC1XOKQYjEPm0YV3E6+K2IExgi7cJiIRQYHAaBaXr72T12ndtvB8l48qGl3S2GKg2dl8JVS2K/Uxy/4k6YHOwmD+SXYTGbO8PgvvhJADqCDZWjrPVJ4l9SsH5S4pp2Ckc3tmVQ/mYK200vSDRE6H6GCDaM5Axgy9ah2HnigT45yqZCbZw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Apr 02 2026, Andrew Morton wrote: > On Thu, 02 Apr 2026 12:06:58 +0000 Pratyush Yadav wrote: > >> On Thu, Mar 26 2026, Chenghao Duan wrote: >> >> > In memfd_luo_preserve_folios(), two variables had types that could cause >> > silent data loss with large files: >> > >> > 1. 'size' was declared as 'long', truncating the 64-bit result of >> > i_size_read(). On 32-bit systems a 4GB file would be truncated to 0, >> > causing the function to return early and discard all data. >> >> As Pasha said, KHO and LUO are not expected to run on 32-bit systems. >> Plus, since i_size_read() returns loff_t, why use u64 when you can just >> match the type and just use loff_t (which on 64-bit is long anyway)? I >> don't get why u64 is any better than long or loff_t. >> >> > >> > 2. 'max_folios' was declared as 'unsigned int', causing overflow for >> > sparse files larger than 4TB. For example, a 16TB+4KB file would >> > calculate 0x100000001 folios but truncate to 1 when assigned to >> > max_folios, causing memfd_pin_folios() to pin only the first folio. >> >> Using unsigned int was intentional. We pass max_folios to >> memfd_pin_folios(), which expects an unsigned int. So this change is >> pointless unless you go and update memfd_pin_folios() too. >> >> I think making memfd_pin_folios() use unsigned long for max_folios makes >> a lot of sense, so can you please go update that first before making >> this change? And when you do, please match the type of the argument to >> the type you use here instead of using u64. This can be a separate, >> independent patch series. > > Thanks. I'll drop this patch. The preceding six patches are looking > well-reviewed and ready to go? Yes. The first six patches are good to go. I think the changes in this one can be split off as a separate series since it will be a bit more involved. > > Chenghao, please prepare any update for this patch against the > preceding six. Or against tomorrow's mm-unstable or mm-new or > linux-next. > -- Regards, Pratyush Yadav