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Wed, 27 Dec 2023 22:41:27 -0800 (PST) Received: from [10.255.185.101] ([139.177.225.235]) by smtp.gmail.com with ESMTPSA id h32-20020a63f920000000b005b9083b81f0sm12314663pgi.36.2023.12.27.22.41.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 Dec 2023 22:41:27 -0800 (PST) Message-ID: <23b76f56-dd91-470b-9967-8482951e5364@bytedance.com> Date: Thu, 28 Dec 2023 14:41:20 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 1/6] mm/zswap: change dstmem size to one page Content-Language: en-US To: Nhat Pham , Andrew Morton Cc: Barry Song <21cnbao@gmail.com>, Seth Jennings , Johannes Weiner , Vitaly Wool , Chris Li , Yosry Ahmed , Dan Streetman , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Chris Li References: <20231213-zswap-dstmem-v4-0-f228b059dd89@bytedance.com> <20231213-zswap-dstmem-v4-1-f228b059dd89@bytedance.com> <20231227125853.2dd07cd61f8a8df95042677c@linux-foundation.org> From: Chengming Zhou In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: EE1C6180012 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: wpajcs3erzcw4akzrhcu55brj8kfnho6 X-HE-Tag: 1703745688-17265 X-HE-Meta: U2FsdGVkX19MbBewGPeuaevlLzhFJ6eUWFLcBlCFkM3P+x/N+mJ7ZSoIbMuwmEFpNzjm5cEKrDLGnPdgt1e22w4ZdtfweNzUJeYCe7Bun0A6kITxa2JbZKcHgUwAr2MR69LuohmXpjcLUAjS8P0dDDjUPuO2z2IXwXRrKIq1AMKHs5yxF3PN/a62WCqDIUUgs13RXxamjFyUzQotxxHvOaCDMTbwDesL5pN2sTpkSEoTBdDAfulIlfR9YK+d9oCSb+/UaILLr77S6RjfBoiH49nSSpVEg3iyvf9wH8iJxNp6xmQwiwY64jp/ZRvuvzq1Wnl20jX8i1ShVFPxaKMfH73kMqEoU6QZRlKfki987w6e9DKHqKUiNYLkEl7ptHYNvhnMmisS6guB/uNhS6WIThRTE5g/M1jCLFk9KZvWpx1CuKqFIOxWghdPGMSK3IQP40giNW+16rcR645Yv3lL/9ZOb5XOUALWDqvGmwz6nhJLzX5aBlGtjmU5cEikwsWYc8s92XUkIpOX6tEELZrgrV35IpKsvgC61ZwWDx1KlNDbM2gSw/WEdr2EMR6hRQqdRR3KuFa6kS0WNSltrKWhw5BFGT1izfZAEmKT13inxAWfDTpouqFGHsVOMMxVkaZja6kGTr5alyEgcEmnyAX5vLeXAbufb13JhG3rGSe4C5eH3xKQwPb5VeI5oSRS/B6SSpty5hcrvKvvCaPQvfKonGQW+A3nzx81MjkOsAZLvYop675E+evPbjDrbOSoqczgiGkztBebMlNjpxuINxcMEFxWvBtDQOm2TVq12y9jdCCyTrECzhz4vQPWWxaHL5NDw/mG4P5/DZoNNwNJEv2eNQqDbPpmIk9088WE6fGxlkE5JIRE0rgJhvUOeB03s6hcRRbt5ewtrkpwJeaUY0Svmp6m8FuC+KjpELx0Y8OGMdT6FXx8NOMVZ2Yk13RioDe+nFA1fCU8QSGga3okdua cvxmGuTU CQGkeXGY9n8LARWgGRr6N6r22cRk5w66XU0+umh6ASugey59fgRSvz2FHc52r6Upa/QIKEoM73poMuAfyy7aoS61dmZcrdFHCwBQm3lrixwTlZoY/dzZnx7qHpB7Bet/BXw5a X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2023/12/28 07:21, Nhat Pham wrote: > On Wed, Dec 27, 2023 at 12:58 PM Andrew Morton > wrote: >> >> On Wed, 27 Dec 2023 14:11:06 +0800 Chengming Zhou wrote: >> >>>> i remember there was an over-compression case, that means the compressed >>>> data can be bigger than the source data. the similar thing is also done in zram >>>> drivers/block/zram/zcomp.c >>> >>> Right, there is a buffer overflow report[1] that I just +to you. >> >> What does "[1]" refer to? Is there a bug report about this series? > > I think Chengming was referring to this: > > https://lore.kernel.org/lkml/0000000000000b05cd060d6b5511@google.com/ > > Syzkaller/syzbot found an edge case where the page's "compressed" form > was larger than one page, which tripped up the compression code (since > we reduced the compression buffer size to 1 page here). Right, thanks Nhat! The reported bug can be fixed by a patch I posted: https://lore.kernel.org/all/20231227093523.2735484-1-chengming.zhou@linux.dev/ Although this bug is fixed, we still have to revert the first patch to use 2 pages buffer in zswap, since not all compressor drivers would respect the buffer size we passed in and may overflow our output buffer. Barry Song has explained the background in: https://lore.kernel.org/all/CAGsJ_4xuuaPnQzkkQVaRyZL6ZdwkiQ_B7_c2baNaCKVg_O7ZQA@mail.gmail.com/ I will send an updated series later. Thanks!