From nobody Fri Dec 19 17:18:28 2025 Received: from mail-pl1-f227.google.com (mail-pl1-f227.google.com [209.85.214.227]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 20AA12652AF for ; Thu, 4 Dec 2025 22:43:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.227 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764888219; cv=none; b=sOJoWW0/iDN698u/eXB0it6ejNd81DGuVTYz97ttwsiBReeUpfWhCuZz62WpLLrPiWBqwcyDEwG47Apr8QPq80Vo5QnVimhGN2vfPm9g94EaoO+dX+JQ0jmLIp10LcN0JPJkoVN1XNA3gjUtM41GU+gkQ7hkgo7Uw+HtRsj7OSY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764888219; c=relaxed/simple; bh=fKji5UW4qQnxmds1k5RC/OxIA1Jh6yZN4K7RxDG0990=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=FBXre1MTEYbEcB1LehVnTXkHds/Fv8i4GnFEm6VtECEHAALwMwXCG0KMJLFT/WA+Ioj78p7pRyvHl1cnyX5N82gOWrV1Tn6W1MV/jH30skPyNE1pDr8s5V14r8jdsfH2+PHyo0OBQg8x6FLpqOZ6kSA53aks65f0lx56sP955S4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=purestorage.com; spf=fail smtp.mailfrom=purestorage.com; dkim=pass (2048-bit key) header.d=purestorage.com header.i=@purestorage.com header.b=b3Nw/9pC; arc=none smtp.client-ip=209.85.214.227 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=purestorage.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=purestorage.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=purestorage.com header.i=@purestorage.com header.b="b3Nw/9pC" Received: by mail-pl1-f227.google.com with SMTP id d9443c01a7336-297e2736308so1614165ad.1 for ; Thu, 04 Dec 2025 14:43:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=purestorage.com; s=google2022; t=1764888217; x=1765493017; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=yUQAkBnTqkldE0MNFpzbBZDBYWqzkXqzRwim8JXEfT8=; b=b3Nw/9pCUw0XrlBFL8YJig0uyClDMBN21MtKHo+/MAMd+VWxPqF8snDv+jddYzDUHe SNV4P+GNy5lgKvuuuwXSVvmH1Z7TP5Lx9gOTEhyK+gDDWP3vISSJcLT3tEcDlczdhUiE e0FadU6Ldt+ynT+uPyzDM+goflROX/SppPfMRJzybQgCTq7zY995QlrYUx0wdHioyqyA ULU6tCmxWJgJMa817wrBF98P2CZm+JNE/KQTzA/UcV+3wAtfavuJPXO+mE0MpP7+XdF5 h9xzh8eV1GMRYAquyJyK/oke3CIa78Fe+1+t8epQOZZSOZLGcvVdB2xVnC6EgWNMu+tR a6hA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1764888217; x=1765493017; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=yUQAkBnTqkldE0MNFpzbBZDBYWqzkXqzRwim8JXEfT8=; b=uZrfCMRDuK6+QC2zTPYBFqeVRtSkDeHrLox9bB2ebSpnHcruI/phdUgg3/UyCBwgwe c8MgZsnV3xGhpJq9DvJEo+QkohO0bmT30LZn+7yck8fA1Mtd3htya6fm7m6mgBQovVvF FHM7qe3xI00UMZ1y8R4oCLM5gKdmnRNEKM2N/KyWo+17fTWUOvXNL5j1BgblScZjEobH 1oNMUOgAu5fH70V0UA69V1or8iF42dZ0Ztx3PXIlCDcepVTiZtZ4FjRFI2MkKkq820d0 rXO6/QtfYM/1RHFatuHnSL3CrRdfaWZ7H+yFj6uJH7oXiBSDF6qaHHcS6tQQygdViST2 1fsQ== X-Forwarded-Encrypted: i=1; AJvYcCXuk03Jg/C9/GsmnlIhbp8OvNkkDXrshjxeC8dLkMAzBp2PpEZXCM/Hlr5ku7j99zj/OUsBgtt2sqI9z+g=@vger.kernel.org X-Gm-Message-State: AOJu0YwpGW1qwdj8ndv7/YlzjaaXgirdBrQLA1NUXXeT9MgM8S13NR4D z4q8ePDLP5DS9aN1NaM3VwqdJgqlCrhuNRlxGAgLQTom26+8oT2+U+yL8K65aE96ibMJZaGu7oB RNtdGoKUr3h550Xd6xOkOycJ5BHo8WKmQsnVB X-Gm-Gg: ASbGncvPDxffaW3Ay1uOTldUx1D3lZ5Bgph7MWUrk5HpQsxe3WmI4ozVkSwe9m/gYEj vp50LOvjW9Siq4I7X681kgJmuhR1a86XDJuHeU4HxG2Odix38p8xDuqv/+Y8ImfE0E3Mj7SMp75 KkAW2mjUXbTdNe4gmdh39kCyZhOmz2VlaMddoKVPqPmlcU/H54LZn9AsiBJLHB/l3OwE7QVkCpn I4ksaxt9JfHDzbNQah/iWLjUNgtKdZBLUyPRWSNuHlcQNrZ4erkzIirexvIK71qgRCfxiVeLWgI TOy/M5ZdlJQQf18yKeLUE6POHAM44haefELwSvelUG9pTg/X50R/p5zjzXM2/B8YmC4m0iC7Mml /PeEI/pzhG1wd1UEurkLhz8vP1OSSgdcoj79U9Zmx5A== X-Google-Smtp-Source: AGHT+IEt9ug7nEQAm2LDkRUFBItANDF870I5/sEI6n4aXjKv+4LBOhHOR3cOuk0Y23FkZAwlHH5prB4sCoTt X-Received: by 2002:a17:902:f606:b0:29d:7e23:629 with SMTP id d9443c01a7336-29d7e2307e3mr42480665ad.0.1764888217329; Thu, 04 Dec 2025 14:43:37 -0800 (PST) Received: from c7-smtp-2023.dev.purestorage.com ([208.88.159.128]) by smtp-relay.gmail.com with ESMTPS id d9443c01a7336-29dae49cc11sm3869575ad.14.2025.12.04.14.43.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Dec 2025 14:43:37 -0800 (PST) X-Relaying-Domain: purestorage.com Received: from dev-csander.dev.purestorage.com (unknown [IPv6:2620:125:9007:640:ffff::1199]) by c7-smtp-2023.dev.purestorage.com (Postfix) with ESMTP id D77613400EA; Thu, 4 Dec 2025 15:43:36 -0700 (MST) Received: by dev-csander.dev.purestorage.com (Postfix, from userid 1557716354) id C6533E42318; Thu, 4 Dec 2025 15:43:36 -0700 (MST) From: Caleb Sander Mateos To: Jens Axboe Cc: Caleb Sander Mateos , Joanne Koong , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] io_uring/kbuf: use READ_ONCE() for userspace-mapped memory Date: Thu, 4 Dec 2025 15:43:31 -0700 Message-ID: <20251204224332.1181383-1-csander@purestorage.com> X-Mailer: git-send-email 2.45.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The struct io_uring_buf elements in a buffer ring are in a memory region accessible from userspace. A malicious/buggy userspace program could therefore write to them at any time, so they should be accessed with READ_ONCE() in the kernel. Commit 98b6fa62c84f ("io_uring/kbuf: always use READ_ONCE() to read ring provided buffer lengths") already switched the reads of the len field to READ_ONCE(). Do the same for bid and addr. Signed-off-by: Caleb Sander Mateos Fixes: c7fb19428d67 ("io_uring: add support for ring mapped supplied buffer= s") Cc: Joanne Koong --- io_uring/kbuf.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c index 8a329556f8df..52b636d00a6b 100644 --- a/io_uring/kbuf.c +++ b/io_uring/kbuf.c @@ -42,11 +42,11 @@ static bool io_kbuf_inc_commit(struct io_buffer_list *b= l, int len) buf_len =3D READ_ONCE(buf->len); this_len =3D min_t(u32, len, buf_len); buf_len -=3D this_len; /* Stop looping for invalid buffer length of 0 */ if (buf_len || !this_len) { - buf->addr +=3D this_len; + buf->addr =3D READ_ONCE(buf->addr) + this_len; buf->len =3D buf_len; return false; } buf->len =3D 0; bl->head++; @@ -196,13 +196,13 @@ static struct io_br_sel io_ring_buffer_select(struct = io_kiocb *req, size_t *len, buf =3D io_ring_head_to_buf(br, head, bl->mask); buf_len =3D READ_ONCE(buf->len); if (*len =3D=3D 0 || *len > buf_len) *len =3D buf_len; req->flags |=3D REQ_F_BUFFER_RING | REQ_F_BUFFERS_COMMIT; - req->buf_index =3D buf->bid; + req->buf_index =3D READ_ONCE(buf->bid); sel.buf_list =3D bl; - sel.addr =3D u64_to_user_ptr(buf->addr); + sel.addr =3D u64_to_user_ptr(READ_ONCE(buf->addr)); =20 if (io_should_commit(req, issue_flags)) { io_kbuf_commit(req, sel.buf_list, *len, 1); sel.buf_list =3D NULL; } @@ -278,11 +278,11 @@ static int io_ring_buffers_peek(struct io_kiocb *req,= struct buf_sel_arg *arg, =20 /* set it to max, if not set, so we can use it unconditionally */ if (!arg->max_len) arg->max_len =3D INT_MAX; =20 - req->buf_index =3D buf->bid; + req->buf_index =3D READ_ONCE(buf->bid); do { u32 len =3D READ_ONCE(buf->len); =20 /* truncate end piece, if needed, for non partial buffers */ if (len > arg->max_len) { @@ -293,11 +293,11 @@ static int io_ring_buffers_peek(struct io_kiocb *req,= struct buf_sel_arg *arg, break; buf->len =3D len; } } =20 - iov->iov_base =3D u64_to_user_ptr(buf->addr); + iov->iov_base =3D u64_to_user_ptr(READ_ONCE(buf->addr)); iov->iov_len =3D len; iov++; =20 arg->out_len +=3D len; arg->max_len -=3D len; --=20 2.45.2