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 54D2D4CCDC7; Fri, 4 Sep 2026 05:42:18 +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=1788500539; cv=none; b=eHl32QfxSMumgIhT/W6/XJi/qqoW3KL1372ZQiZjwp/zdkdJioMqkyonHhcoPxsNBTMpT4X3vGxLNYIVhhd+cVmPSZUQn+/33+uaX0lnbZ7l9TIkTk2RCrATK7xC6ZZuVS5vE+RZIuaqdraL07UHCoeVGOoF/U4Qj+pKZ23r97w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788500539; c=relaxed/simple; bh=CUNPZJKR8zvr8rSmZnv6kusiFKqVx0SWWNFkMIgrx5A=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=QCYZsuqT+WAslBHK8F21D44gC1wObDZkNVqssoHS5+exhhT3O/8A8eKr934Uc82pF/kGfx/Yt3WMDOD0VtBTrNIxnDrlKxgySfXfwNKlpZb4lmQqIAo4rbok1WdsTpynQ/3i+2/axsL066Z7J0+OVOjCssG6IfGAMMEg+EkaoHM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=nH66cQfG; 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="nH66cQfG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A77FB1F00A3D; Fri, 4 Sep 2026 05:42:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788500538; bh=1Tvc8Ksz3nWOgmCfzNIsOruyOKSqmS3USnNp6HC84DI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=nH66cQfGvr9XWg/luoBYxtSDT9MDmXC5QfUXwlxX6cK0QF4LEsRK8ZdB/bXWGLKN3 HjoVoRqr1QwLeQUVlv4WZbG99/ZsPxRMWsg5NDvjkVxP2A2X/BjAnebHJA4TJSeWzD pCSR/QLIDL2lUArQkYnRoWkJ2Nvok1TPzJEKFmDE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?Krzysztof=20Wilczy=C5=84ski?= Subject: [PATCH 6.18 092/552] PCI/sysfs: Fix out-of-bounds read in pci_write_legacy_io() Date: Fri, 4 Sep 2026 06:54:09 +0200 Message-ID: <20260904045749.965729678@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045747.813364717@linuxfoundation.org> References: <20260904045747.813364717@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Krzysztof Wilczyński commit dc76258d0132df1d831a5a29758bd448ca9c566e upstream. pci_write_legacy_io() loads 4 bytes from the kernfs write buffer regardless of how many bytes userspace wrote: if (count != 1 && count != 2 && count != 4) return -EINVAL; return pci_legacy_write(bus, off, *(u32 *)buf, count); kernfs_fop_write_iter() allocates the buffer with kmalloc(len + 1), so a 1-byte write to the legacy_io sysfs file allocates 2 bytes and the unconditional u32 load reads up to 2 bytes past the end of the allocation, which KASAN reports as a slab-out-of-bounds read. Similarly, a 2-byte write overreads by 1 byte. Thus, read only the number of bytes requested using get_unaligned_le16() and get_unaligned_le32() for the 2 and 4 byte cases, interpreting the buffer as little-endian to match the byte ordering of PCI I/O port space. The PowerPC implementation previously compensated for the generic code's native-endian 32-bit load by shifting the value into place for the 1 and 2 byte cases. The shifts were only correct on big-endian kernels. On little-endian PowerPC (POWER8 and later), they extracted the wrong bytes, so a 1-byte write wrote an out-of-bounds byte instead of the requested value. On big-endian, the native load also caused out_le16() and out_le32() to reverse the user's bytes on the wire for 2 and 4 byte writes. The little-endian helpers resolve both issues, so the shifts are removed. No changes are needed for the Alpha platform. The legacy_io file is root-only and exists only on Alpha and PowerPC, the two architectures that define HAVE_PCI_LEGACY. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260616163131.2763281-1-kwilczynski@kernel.org Signed-off-by: Krzysztof Wilczyński Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kernel/pci-common.c | 9 ++------- drivers/pci/pci-sysfs.c | 18 +++++++++++++++--- 2 files changed, 17 insertions(+), 10 deletions(-) --- a/arch/powerpc/kernel/pci-common.c +++ b/arch/powerpc/kernel/pci-common.c @@ -626,19 +626,14 @@ int pci_legacy_write(struct pci_bus *bus return -ENXIO; addr = hose->io_base_virt + port; - /* WARNING: The generic code is idiotic. It gets passed a pointer - * to what can be a 1, 2 or 4 byte quantity and always reads that - * as a u32, which means that we have to correct the location of - * the data read within those 32 bits for size 1 and 2 - */ switch(size) { case 1: - out_8(addr, val >> 24); + out_8(addr, val); return 1; case 2: if (port & 1) return -EINVAL; - out_le16(addr, val >> 16); + out_le16(addr, val); return 2; case 4: if (port & 3) --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -931,12 +931,24 @@ static ssize_t pci_write_legacy_io(struc char *buf, loff_t off, size_t count) { struct pci_bus *bus = to_pci_bus(kobj_to_dev(kobj)); + u32 val; - /* Only support 1, 2 or 4 byte accesses */ - if (count != 1 && count != 2 && count != 4) + /* Only support 1, 2 or 4 byte accesses. */ + switch (count) { + case 1: + val = *(u8 *)buf; + break; + case 2: + val = get_unaligned_le16(buf); + break; + case 4: + val = get_unaligned_le32(buf); + break; + default: return -EINVAL; + } - return pci_legacy_write(bus, off, *(u32 *)buf, count); + return pci_legacy_write(bus, off, val, count); } /**