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Wed, 05 Aug 2026 19:41:47 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:8002:2a47:a704:5a58]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2d0aa4cf714sm23091755ad.67.2026.08.05.19.41.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Aug 2026 19:41:47 -0700 (PDT) Date: Thu, 6 Aug 2026 11:41:43 +0900 From: Sergey Senozhatsky To: Andrew Morton Cc: Longlong Xia , minchan@kernel.org, senozhatsky@chromium.org, axboe@kernel.dk, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Longlong Xia Subject: Re: [PATCH 1/1] zram: reject disksizes that exceed slot index range Message-ID: References: <20260804143832.146129-1-xialonglong2025@163.com> <20260805115424.a0c8abdb9bbd2f7caa6fb66a@linux-foundation.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260805115424.a0c8abdb9bbd2f7caa6fb66a@linux-foundation.org> On (26/08/05 11:54), Andrew Morton wrote: > > From: Longlong Xia > > > > zram uses u32 slot indexes, while disksize_store() accepts a u64 > > size. On 32-bit systems, a disksize larger than U32_MAX pages is > > truncated when zram_meta_alloc() assigns the page count to size_t. > > array_size() then sees only the truncated count, so a small table can > > be allocated while the original capacity is published. Valid I/O > > within that capacity can subsequently access beyond zram->table. > > > > The same oversized capacity also lets full-device scanners compare a > > u32 index with an upper bound larger than U32_MAX, so the index can > > wrap instead of terminating. > > > > Reject disksizes larger than U32_MAX pages before aligning and > > allocating the table. This keeps the table size, published capacity and > > slot index range consistent. > > Oh. Rejecting large devices sounds severe. Can't we just fix the > 32-bit trucation issues? zram historically used u32, I never thought that anyone would want a 16TB+ device. But we don't really have reasons to limit it. I can look into converting to unsigned long, Longlong is already looking into it.