From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 684F6438026 for ; Mon, 20 Jul 2026 16:28:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784564921; cv=none; b=DYtGJcbgz3F3zYMqXWYlp8DCXKiq0ieSUY4tGrwv79gvQOR0kOo6k5uu5D0QDipSbxxs3pRMiivohorf5B7I0ujXRNIFFQGuDdWqfCUX+8UFljLsb6QbkqxxFlkGzWbyZQFmallD06hMuYJiEWAI7JIfN1PIGgljBNVGrkADhPI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784564921; c=relaxed/simple; bh=6nykS5uC09nMViVEyTFhRlsQTQJY7xFOBvIUP3rdIH4=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=X4KmxvH12+ftHI2SKEcZL/XJAJJ1yzNBUdUg65PB3jRYh5ihgAAQRHAC5wvq8H11OLkKMxKX6iFyrR08ISyTY9MZ8BRDmdeucEZHkKIJxFuXgKiNiaVjzrspqSBcKdR8155fmxIgtdXTaWvJiU2akqrZcTL+LbfhfpbHO8iEWUk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=0x4K/nQm; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="0x4K/nQm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 604361F00A3D; Mon, 20 Jul 2026 16:28:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784564916; bh=2JYTahUpy0xHa13dJrmuW1hguoN0lNM5Mtp/3dOZJpM=; h=From:To:Cc:Subject:Date:Reply-To; b=0x4K/nQmUxndqmDW4IhoKjgHS8xoQDv1cpBl+8/rVh+z+B19SWaRIafBLT8SPuxl5 8zZBjY3zrUsnti5OW/gd5RbY1K7TVyA6PX57CvRGGpFkLmHygSU4hKBB7yV9xAN88s NRKDUjT3sh3kckdpCoAZadSDlStVJqjav9Okvd8g= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-64191: i2c: stub: Reject I2C block transfers with invalid length Date: Mon, 20 Jul 2026 18:27:54 +0200 Message-ID: <2026072052-CVE-2026-64191-42fe@gregkh> X-Mailer: git-send-email 2.55.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4954; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=ubRRDKM6Z4gBS5WF/mqu2bzoCj/AsM9XK6kX4B1FzDE=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlxPh1VX3uPbD57X+J1zuOnrbLFurt07i1XZJZdUytmU d78M+5qRywLgyATg6yYIsuXbTxH91ccUvQytD0NM4eVCWQIAxenAEzE5DDDPF0/ZdYvEiL5+6pr xXn4779un+Ejz7Bgt7rBiuJnuyfPtCx+vCHfOMmT8aciAA== X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: i2c: stub: Reject I2C block transfers with invalid length The I2C_SMBUS_I2C_BLOCK_DATA case in stub_xfer() uses data->block[0] as the transfer length. The existing check only clamps it to avoid overrunning the chip->words[256] register array, but does not validate it against I2C_SMBUS_BLOCK_MAX (32), which is the limit of the union i2c_smbus_data.block buffer (34 bytes total). The driver is a development/test tool (CONFIG_I2C_STUB=m, not built by default) that must be loaded with a chip_addr= parameter. A local user with access to /dev/i2c-* can issue an I2C_SMBUS ioctl with I2C_SMBUS_I2C_BLOCK_DATA and data->block[0] > 32, causing stub_xfer() to read or write past the end of the union i2c_smbus_data.block buffer: BUG: KASAN: stack-out-of-bounds in stub_xfer (drivers/i2c/i2c-stub.c:223) Read of size 1 at addr ffff88800abcfd92 by task exploit/81 Call Trace: stub_xfer (drivers/i2c/i2c-stub.c:223) __i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:593) i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:536) i2cdev_ioctl_smbus (drivers/i2c/i2c-dev.c:391) i2cdev_ioctl (drivers/i2c/i2c-dev.c:478) __x64_sys_ioctl (fs/ioctl.c:583) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) The bug exists because i2c-stub implements .smbus_xfer directly, bypassing the I2C_SMBUS_BLOCK_MAX validation in i2c_smbus_xfer_emulated(). The I2C_SMBUS_BLOCK_DATA case in the same function correctly validates against I2C_SMBUS_BLOCK_MAX, but the I2C_SMBUS_I2C_BLOCK_DATA case does not. Fix by rejecting transfers with data->block[0] == 0 or data->block[0] > I2C_SMBUS_BLOCK_MAX with -EINVAL, consistent with both the I2C_SMBUS_BLOCK_DATA case in the same function and the I2C_SMBUS_I2C_BLOCK_DATA validation in i2c_smbus_xfer_emulated(). The Linux kernel CVE team has assigned CVE-2026-64191 to this issue. Affected and fixed versions =========================== Issue introduced in 2.6.33 with commit 4710317891e4824ce1510a6b5066abbd3e917750 and fixed in 5.10.260 with commit 7e9072dbd5f2f17934751873450d2c22080ead80 Issue introduced in 2.6.33 with commit 4710317891e4824ce1510a6b5066abbd3e917750 and fixed in 5.15.211 with commit 21e87f336ac6303fed54a69b1d0d79a23b25c8d0 Issue introduced in 2.6.33 with commit 4710317891e4824ce1510a6b5066abbd3e917750 and fixed in 6.1.177 with commit 3fd225f3e4cd67ec8ddab1afed9da03c7c43537c Issue introduced in 2.6.33 with commit 4710317891e4824ce1510a6b5066abbd3e917750 and fixed in 6.6.144 with commit 1c4ffe6b4f04365485ed58d64c9bb86b46fc9037 Issue introduced in 2.6.33 with commit 4710317891e4824ce1510a6b5066abbd3e917750 and fixed in 6.12.95 with commit 4bd8635f28c135a08aac6badcd7d9b5cdb34335f Issue introduced in 2.6.33 with commit 4710317891e4824ce1510a6b5066abbd3e917750 and fixed in 6.18.37 with commit 5f4d2bd028ebb6e4c09a9d64842546022321d4a7 Issue introduced in 2.6.33 with commit 4710317891e4824ce1510a6b5066abbd3e917750 and fixed in 7.0.14 with commit 0526931b16e5a118d367b7bfce7d797e63f7ac69 Issue introduced in 2.6.33 with commit 4710317891e4824ce1510a6b5066abbd3e917750 and fixed in 7.1 with commit 6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2026-64191 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: drivers/i2c/i2c-stub.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/7e9072dbd5f2f17934751873450d2c22080ead80 https://git.kernel.org/stable/c/21e87f336ac6303fed54a69b1d0d79a23b25c8d0 https://git.kernel.org/stable/c/3fd225f3e4cd67ec8ddab1afed9da03c7c43537c https://git.kernel.org/stable/c/1c4ffe6b4f04365485ed58d64c9bb86b46fc9037 https://git.kernel.org/stable/c/4bd8635f28c135a08aac6badcd7d9b5cdb34335f https://git.kernel.org/stable/c/5f4d2bd028ebb6e4c09a9d64842546022321d4a7 https://git.kernel.org/stable/c/0526931b16e5a118d367b7bfce7d797e63f7ac69 https://git.kernel.org/stable/c/6036b5067a8199ba7a2dc7b377d4b9dd276d5f9e