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 679992FDC20; Thu, 16 Jul 2026 14:26:48 +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=1784212009; cv=none; b=NWJsTgniBN+vWNW9P0B6okeRoy6QXlnLOK5wYbapmmlSWpUx5VoEh6Iq8AiPRysCk9GdJ6L1h58FveuR9++wqt3J5d1lSnlVkyAKTHwX5UmGdNsVxG3hQJwIl3R3RRavGTnW7IiqzgW+8CZxi8mWtuFKFH1CukwkemXYAv0U4CI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784212009; c=relaxed/simple; bh=qba0TF9F/KoQlVdHncpDnWy6a3NChxwu+UCT76GMfNY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ndPPwGozBo7RTuQ77HAMQ6aX68IC4WMoQWw92FHZm7SGfF0QYLwkp9TgCa4fjt1VoIK/XOA6PTEtwFy88KTBc6YzBCkfAftZAcw+krlyzPe6GBiFv+QYfPAE/xWa+Ya1OprMr3XIserb6IBgn1wFphtJiEiLb6p61Kqv/g5rwI0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=IiW+BVsv; 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="IiW+BVsv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9230F1F00A3E; Thu, 16 Jul 2026 14:26:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784212008; bh=vINGTTpNEXaeEvYNYkEhZRnNkA4wgP7aXR7HqeR5smc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=IiW+BVsv/8v5gT8bMEIv8239tpe7REUpGGLwFSFKFn0wNndUThPQo29IInkPWV9W8 svOyEeoXh1VzgEY4BambIzfa9I8MG6fzP1SnrviiU4Qu/3rAuqNpwMLEVX4qYH06zV e0ZmIrodMDaTBmycFzbNBaSRVFmJNISU1OZChPuM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gil Portnoy , Namjae Jeon , Steve French Subject: [PATCH 6.12 164/349] ksmbd: add a permission check for FSCTL_SET_ZERO_DATA Date: Thu, 16 Jul 2026 15:31:38 +0200 Message-ID: <20260716133037.052784538@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260716133033.287196923@linuxfoundation.org> References: <20260716133033.287196923@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-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gil Portnoy commit 3320ba068198adc144c89d6661b805acce01735b upstream. FSCTL_SET_ZERO_DATA in smb2_ioctl() destroys file data via ksmbd_vfs_zero_data() -> vfs_fallocate(PUNCH_HOLE/ZERO_RANGE) after checking only the share-level KSMBD_TREE_CONN_FLAG_WRITABLE, with no per-handle access check. A handle opened with only FILE_WRITE_ATTRIBUTES still yields an FMODE_WRITE filp (FILE_WRITE_ATTRIBUTES is part of FILE_WRITE_DESIRE_ACCESS_LE, so smb2_create_open_flags() opens it O_WRONLY), so the vfs_fallocate FMODE_WRITE check does not stop it; only the missing fp->daccess gate would. Reproduced on mainline 7.1-rc7 with KASAN by an authenticated SMB client: a FILE_WRITE_ATTRIBUTES-only handle zeroed 4096 bytes of file data it had no FILE_WRITE_DATA right to (6/6; a FILE_READ_DATA-only handle was correctly denied). This is the unfixed sibling of commit cc57232cae23 ("ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE"). Because SET_ZERO_DATA writes data (not an attribute), require FILE_WRITE_DATA. Cc: stable@vger.kernel.org Signed-off-by: Gil Portnoy Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman --- fs/smb/server/smb2pdu.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -8417,6 +8417,12 @@ int smb2_ioctl(struct ksmbd_work *work) goto out; } + if (!(fp->daccess & FILE_WRITE_DATA_LE)) { + ksmbd_fd_put(work, fp); + ret = -EACCES; + goto out; + } + ret = ksmbd_vfs_zero_data(work, fp, off, len); ksmbd_fd_put(work, fp); if (ret < 0)