From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=pass header.oldest-pass=0 smtp.remote-ip=165.173.180.11 ARC-Seal: i=2; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=pass; t=1792541240; b=qGMsJq4Uuz5JOvF2DgROlbuSFYPqwhDvBZbabN0cQJn2EE2RrNi4xLBLxXz3SBOaZJJh Ruf/FRFldnJ8o4XIepmpvxvfIHi0azZa9ikslpsAL5z4SDQUMj4Fe2ZVNYN/cH6mldkw3 9R98zyvTnPrTPNBu/YgZn5ewXH4LOgVGgVQ/sM3feghMhrpTbOVsHLi1caK3d0OdRl+HY jWXaW3zhKFkq/IEWfbRBnuiRyDCTMtYFlzbK1A6QLlwk/m7F6M7eouSCkdaFNxaQtNOuD 6FnBqzdY1+E23hW7+2mGbMURUNzDEstCRVgq2Wm51HMR4vH2kfHkWtwwuxn+VS0TNJQ== ARC-Message-Signature: i=2; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792541240; h=DMARC-Filter:DKIM-Signature:Received:From:Date:Subject:MIME-Version: Content-Type:Content-Transfer-Encoding:Message-Id:References: In-Reply-To:To:Cc:X-Mailer:X-Developer-Signature:X-Developer-Key; bh=2lDEC0DuiMPcWNbSfDdjSTczo+Sc4lF7TDFSyMLbmz4=; b=3bk8UGH8QbB3IU3A+oCGSP+h1U3Lqy+wUN07a+jQuY9hS1K7OtV6T2RpqOG5H5EiViA6 ypph8JLrwIorSLJ4eFTNkWxyxXkswyigACzxqyYcPMV2QlCZqmXwCAqNccdw+uX4t1AvQ j85WL8dIppADTylx2vN3oOtpkRwqDXQ+rdA63T3fKSnaK4trsInuKgcpQZJ9vDxe2q4y0 R5Pnksk3cA2WdNiAK7YlTx19E3m5/hCaKemC6POdHFvIn5oZnf9N/oSDxRwBue8Sy4DM8 KZ990NUry5SvCkeJhBoYv8a4nKB4JDTEqtE0CeAE6hz0Dj2TGpusTzi1LwvVgn5p9Dg== ARC-Authentication-Results: i=2; smtp.subspace.kernel.org; dmarc=pass header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass header.d=collabora.com header.i=deborah.brouwer@collabora.com header.a=rsa-sha256 header.s=zohomail header.b=PxwNPOQ9; arc=pass header.oldest-pass=0 smtp.remote-ip=165.173.180.11 Received: from sender6-op-o11.zoho.com (sender6-op-o11.zoho.com [165.173.180.11]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1D8AB606A31C; Wed, 21 Oct 2026 00:07:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 1D8AB606A31C Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=collabora.com header.i=deborah.brouwer@collabora.com header.a=rsa-sha256 header.s=zohomail header.b=PxwNPOQ9 ARC-Seal: i=1; a=rsa-sha256; t=1792541210; cv=none; d=zohomail.com; s=zohoarc; b=G+3U0M//Gf6SjnFjXackPZD+hwSfuehH2KmsRUyiCh92lzVjIK5Xj/x0Nk/pusKBaPQ7gZEz4eja1vzJejHvav/EZ2etAoIU1hqYCWNz+rYk0q2DhzoOaGH6nIaHB6Z/k8gXTvqGHK4ovMx3CfOanrx8Hu1UNVg63IJtZCN+eVw= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1792541210; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:Subject:Subject:To:To:Message-Id:Reply-To; bh=2lDEC0DuiMPcWNbSfDdjSTczo+Sc4lF7TDFSyMLbmz4=; b=nAGiUTpdpdXzQpD80nr2YG89xBCptD0Y8Nd2g56JyhKKDRZrRmGDA5G1h5iD7B09ehfaBx7jmxEmqE0Gbii5gBY7fc87TMKR+k3hMq+t6jIBpKXi4Qj2nm4g/aUKEA1n54U2g0vuyXF82Q/0ZTH6ubzsa+dBxjW2g0YhwPqyFvI= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=collabora.com; spf=pass smtp.mailfrom=deborah.brouwer@collabora.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1792541210; s=zohomail; d=collabora.com; i=deborah.brouwer@collabora.com; h=From:From:Date:Date:Subject:Subject:MIME-Version:Content-Type:Content-Transfer-Encoding:Message-Id:Message-Id:In-Reply-To:To:To:Cc:Cc:Reply-To; bh=2lDEC0DuiMPcWNbSfDdjSTczo+Sc4lF7TDFSyMLbmz4=; b=PxwNPOQ9hDOm3OBvHhHVu/ywj4V0vRnFCSs++tasDkr7UCS8B3EGOq4QzxrXrnPq m06cSk0Z1B/qBNBLVT5O1msEderWI5pf0yFBRpEPx8lBB5DFyKqlcOdgYV1ZjIMAn/l QkCc/tZs9aOgvkzEQBxo9yf1Pl0PXf0HrqKMC8l0= Received: by smtp.zohomail.com with SMTPS id 1792541208022378.16433192325917; Tue, 20 Oct 2026 17:06:48 -0700 (PDT) From: Deborah Brouwer Date: Tue, 20 Oct 2026 17:06:45 -0700 Subject: [PATCH v4 1/3] rust: uaccess: add UserSliceWriter::clear() X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261020-b4-dev_query_fixes-v4-1-df66b4c98bc6@collabora.com> References: <20261020-b4-dev_query_fixes-v4-0-df66b4c98bc6@collabora.com> In-Reply-To: <20261020-b4-dev_query_fixes-v4-0-df66b4c98bc6@collabora.com> To: Miguel Ojeda , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Daniel Almeida , Tamir Duberstein , Alexandre Courbot , =?utf-8?q?Onur_=C3=96zkan?= , David Airlie , Simona Vetter Cc: rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Deborah Brouwer X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=2481; i=deborah.brouwer@collabora.com; h=from:subject:message-id; bh=BifXMQ3wf5nytHVx4Vm26QkPbWTrCBV8j2ShsC9B2/4=; b=owGbwMvMwCVWuULzOU9c7WvG02pJDFk3mES3aNlFc1y+0Hzz79LKz/JqV7/t5no6yVrl69sNL dcXTqk27yhlYRDjYpAVU2Q5a2/UI1713kh3/v9mmDmsTCBDGLg4BWAiE7czMjS8aLv2tct3ysQ1 Emn3FqzeJ+Yao1Cyo0XN5nBGGPfDu+wM/+On/Dj7PShmoWfhblklT8lnpeZl/j4v+7nN17/f+dr iJwcA X-Developer-Key: i=deborah.brouwer@collabora.com; a=openpgp; fpr=CD3F328C177AEF322D9FFF8379A829E70C5E7DEB Add a method to zero the remaining bytes in a UserSliceWriter. If userspace provides a buffer that is larger than necessary, provide a method to zero out the remaining UserSliceWriter buffer. This avoids userspace consuming potentially uninitialized memory and/or mistaking it for data intentionally provided by the kernel. Use the #[inline] annotation to make this clear() method available for inlining outside of the kernel crate. Since clear_user() is architecturally defined and may be a macro or inline function, add a rust helper to make clear_user() callable from rust. Reviewed-by: Alice Ryhl Signed-off-by: Deborah Brouwer --- rust/helpers/uaccess.c | 6 ++++++ rust/kernel/uaccess.rs | 24 ++++++++++++++++++++++++ 2 files changed, 30 insertions(+) diff --git a/rust/helpers/uaccess.c b/rust/helpers/uaccess.c index 6e59cc9c665c..e799d9ac9804 100644 --- a/rust/helpers/uaccess.c +++ b/rust/helpers/uaccess.c @@ -27,3 +27,9 @@ unsigned long rust_helper__copy_to_user(void __user *to, const void *from, unsig return _inline_copy_to_user(to, from, n); } #endif + +__rust_helper unsigned long +rust_helper_clear_user(void __user *to, unsigned long n) +{ + return clear_user(to, n); +} diff --git a/rust/kernel/uaccess.rs b/rust/kernel/uaccess.rs index f1aecda7a90c..8e18285ec44b 100644 --- a/rust/kernel/uaccess.rs +++ b/rust/kernel/uaccess.rs @@ -638,6 +638,30 @@ pub fn write(&mut self, value: &T) -> Result { pub fn write_truncated(&mut self, value: &T) -> Result { self.write_slice_partial(value.as_bytes(), 0) } + + /// Zeros remaining bytes in the userspace buffer. + /// + /// Fails with [`EFAULT`] if the userspace memory cannot be cleared. + #[inline] + pub fn clear(&mut self) -> Result { + let len = self.length; + + if len == 0 { + return Ok(()); + } + // SAFETY: `clear_user` checks the userspace address and range and handles + // faults when accessing userspace memory + let res = unsafe { bindings::clear_user(self.ptr.as_mut_ptr(), len) }; + + if res != 0 { + return Err(EFAULT); + } + + self.ptr = self.ptr.wrapping_byte_add(len); + self.length = 0; + + Ok(()) + } } /// Reads a nul-terminated string into `dst` and returns the length. -- 2.56.0