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Mon, 21 Sep 2026 21:46:04 -0700 (PDT) From: Yuchao Zhang To: Yu Kuai , Song Liu Cc: Xiao Ni , NeilBrown , linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Yuchao Zhang Subject: Re: [PATCH 1/2] md: fix bblog_size-driven OOB read in super_1_load() and super_1_sync() Date: Tue, 22 Sep 2026 12:45:56 +0800 Message-ID: <20260922044556.30746-1-ndaugoing@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: 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=UTF-8 Content-Transfer-Encoding: 8bit Hi Kuai, Thanks for the review. The 'else if (sb->bblog_offset != 0)' branch handles the valid on-disk state where bblog space was reserved at array creation but no bad blocks have been recorded yet (MD_FEATURE_BAD_BLOCKS clear). A corrupted or forged superblock - hardware fault, fuzzing, or a malicious shared disk - can carry an oversized bblog_size (e.g. 0xFFFF) in that state, bypassing the existing validation in the MD_FEATURE_BAD_BLOCKS branch. When the first bad block is later recorded, super_1_sync() copies sb->bblog_size into bb->size, and md_write_metadata() then builds a bio larger than the backing rdev->bb_page, reading past it and leaking kernel memory contents to disk. You are right that fixing super_1_load() alone is sufficient: the kernel never modifies sb->bblog_size between load and sync, and with the -EINVAL check the device never enters the array, so super_1_sync() is never reached with an oversized value. v2 keeps only the super_1_load() validation. Thanks, Yuchao