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([2409:8a00:79b4:1a90:a428:f9f:5def:1227]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-296019982c7sm29883325ad.25.2025.11.04.07.05.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Nov 2025 07:05:53 -0800 (PST) Message-ID: Date: Tue, 4 Nov 2025 23:05:49 +0800 Precedence: bulk X-Mailing-List: linux-fscrypt@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] fscrypt: fix left shift underflow when inode->i_blkbits > PAGE_SHIFT To: Christoph Hellwig , Eric Biggers Cc: Jaegeuk Kim , Theodore Ts'o , linux-fscrypt@vger.kernel.org, Yongpeng Yang , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, Luis Chamberlain References: <20251030072956.454679-1-yangyongpeng.storage@gmail.com> <20251103164829.GC1735@sol> Content-Language: en-US From: Yongpeng Yang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 11/4/2025 7:12 PM, Christoph Hellwig wrote: > On Mon, Nov 03, 2025 at 08:48:29AM -0800, Eric Biggers wrote: >>> *inode_ret = inode; >>> - *lblk_num_ret = ((u64)folio->index << (PAGE_SHIFT - inode->i_blkbits)) + >>> + *lblk_num_ret = (((u64)folio->index << PAGE_SHIFT) >> inode->i_blkbits) + > > This should be using folio_pos() instead of open coding the arithmetics. > How about this modification: using "<< PAGE_SHIFT" instead of "* PAGE_SIZE" for page_offset and folio_pos? --- a/fs/crypto/inline_crypt.c +++ b/fs/crypto/inline_crypt.c @@ -333,7 +333,7 @@ static bool bh_get_inode_and_lblk_num(const struct buffer_head *bh, inode = mapping->host; *inode_ret = inode; - *lblk_num_ret = ((u64)folio->index << (PAGE_SHIFT - inode->i_blkbits)) + + *lblk_num_ret = ((u64)folio_pos(folio) >> inode->i_blkbits) + (bh_offset(bh) >> inode->i_blkbits); return true; } diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 09b581c1d878..72eeb1841bc3 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -1026,7 +1026,7 @@ static inline pgoff_t page_pgoff(const struct folio *folio, */ static inline loff_t folio_pos(const struct folio *folio) { - return ((loff_t)folio->index) * PAGE_SIZE; + return ((loff_t)folio->index) << PAGE_SHIFT; } /* @@ -1036,7 +1036,7 @@ static inline loff_t page_offset(struct page *page) { struct folio *folio = page_folio(page); - return folio_pos(folio) + folio_page_idx(folio, page) * PAGE_SIZE; + return folio_pos(folio) + (folio_page_idx(folio, page) << PAGE_SHIFT); } Yongpeng,