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 B6F383AFB0C; Tue, 21 Jul 2026 20:19:45 +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=1784665186; cv=none; b=UUsB3GzvYKzB4+NHDWcA3eQMuTic8jbcArF4mCPRcLBPumoWpJwifDmmCTWmu5ovFPoMWHNRXmFG0Jt1bYNC0i+/YDAL08V0TCKsEgr0Gyf/L7vgvfKte47AYx495GbkorV+jnymhRJ0sJPmeCEqyCsKbFdSEAzRkLOk4+eS+Fc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784665186; c=relaxed/simple; bh=OYzUcBIciUpP6aNFVCeeTwkhRsM006HDQtI/Drsc8U0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tKcfBt3kvZ7h7GBCxibMPz0/YEhFZXbdw6h4fjxDVS8QeMTkMA6jbo8G767eaLf6n0Cos98o0HK5Ol8WCfVdmJCj2fCNTJlfyFTT9EFpv7EPQEfWqDRaDI+MPh5Cq3ILD7229tTnrSZct5XWnEqWjqEKyVi159n3k69dhT41jLw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=iNbZcJGO; 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="iNbZcJGO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 293581F000E9; Tue, 21 Jul 2026 20:19:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784665185; bh=L/mrSNzoNsm080BAI8d7sfzE3qgJITys1dTJh5GZdCU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=iNbZcJGOcetVTUq/yIMZXlLL1N0eLRkjIcoNgPSARyr05vZzQtEB3QogzU4QqyrG8 NtQ7e9gQGAcEVO2A5N5HeOg7Rfap4yxZA3pX8epeTazIZ8vGVwqBRmROAjGp/b4fJA p1zMLamIXknrYdKtQ8GIg0NVlbhkg+RiDJ5Ooa8g= 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 6.6 0182/1266] ksmbd: add a permission check for FSCTL_SET_ZERO_DATA Date: Tue, 21 Jul 2026 17:10:19 +0200 Message-ID: <20260721152445.877398678@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152441.786066624@linuxfoundation.org> References: <20260721152441.786066624@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 6.6-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 @@ -8407,6 +8407,12 @@ 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)