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Thu, 02 Apr 2026 12:12:30 +0200 Received: from [::1] (helo=dude02.red.stw.pengutronix.de) by dude02.red.stw.pengutronix.de with esmtp (Exim 4.98.2) (envelope-from ) id 1w8F2M-00000004I4C-04az; Thu, 02 Apr 2026 12:12:30 +0200 From: Sascha Hauer Date: Thu, 02 Apr 2026 12:12:29 +0200 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260402-fs-ext4-buffer-overflows-v1-1-b9f8a909fe58@pengutronix.de> References: <20260402-fs-ext4-buffer-overflows-v1-0-b9f8a909fe58@pengutronix.de> In-Reply-To: <20260402-fs-ext4-buffer-overflows-v1-0-b9f8a909fe58@pengutronix.de> To: BAREBOX X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1775124749; l=1413; i=s.hauer@pengutronix.de; s=20230412; h=from:subject:message-id; bh=Dq7lFzZTts3lICz1zi6ii9s90bMMOBrv8HTjT/CwObI=; b=4AGHS5Mk2fmmeUhn3oIWjt9Qi98orOGhhH2BN8ozP2xFYOXciIUfHiCVXZZVmpNPUfb8+4ccY TT9EBkO1VT7CjCkl9Xp6nIlQJmeEer8MFzMxDkZQ3M1Gk+v/xyad8me X-Developer-Key: i=s.hauer@pengutronix.de; a=ed25519; pk=4kuc9ocmECiBJKWxYgqyhtZOHj5AWi7+d0n/UjhkwTg= X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260402_111238_995630_24CAC560 X-CRM114-Status: GOOD ( 10.80 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Claude Opus 4.6 \(1M context\)" Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:3::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.whiteo.stw.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-5.2 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Subject: [PATCH 1/5] fs: ext4: validate log2_block_size from superblock at mount X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.whiteo.stw.pengutronix.de) The superblock's log2_block_size field is read from disk and used throughout the ext4 code without validation. EXT2_BLOCK_SIZE() computes 1 << (log2_block_size + 10), so a crafted value of 22 or larger causes undefined behavior from shifting an int by >= 32 bits. This leads to wrong allocation sizes for indirect block buffers and enables downstream buffer overflows in every function that reads block-sized data. Validate that log2_block_size does not exceed the maximum defined by EXT2_MAX_BLOCK_LOG_SIZE (65536 byte blocks) at mount time, rejecting the filesystem early if it does. Signed-off-by: Sascha Hauer Co-Authored-By: Claude Opus 4.6 (1M context) --- fs/ext4/ext4_common.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c index a38593105f..094293a069 100644 --- a/fs/ext4/ext4_common.c +++ b/fs/ext4/ext4_common.c @@ -514,6 +514,14 @@ int ext4fs_mount(struct ext_filesystem *fs) goto fail; } + if (le32_to_cpu(data->sblock.log2_block_size) > + EXT2_MAX_BLOCK_LOG_SIZE - EXT2_MIN_BLOCK_LOG_SIZE) { + dev_err(fs->dev, "invalid block size %u\n", + le32_to_cpu(data->sblock.log2_block_size)); + ret = -EINVAL; + goto fail; + } + if (le32_to_cpu(data->sblock.revision_level) == 0) { fs->inodesz = 128; fs->gdsize = 32; -- 2.47.3