Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758912Ab3DBWyB (ORCPT ); Tue, 2 Apr 2013 18:54:01 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:34082 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757911Ab3DBWu5 (ORCPT ); Tue, 2 Apr 2013 18:50:57 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Frederic Crozat , Matthew Garrett , Josh Boyer , Michael Schroeder , "Lee, Chun-Yi" , Lingzhu Xiang , Seiji Aguchi , Matt Fleming , CAI Qian Subject: [ 36/56] efivars: explicitly calculate length of VariableName Date: Tue, 2 Apr 2013 15:50:03 -0700 Message-Id: <20130402224716.051505943@linuxfoundation.org> X-Mailer: git-send-email 1.8.1.rc1.5.g7e0651a In-Reply-To: <20130402224711.840825715@linuxfoundation.org> References: <20130402224711.840825715@linuxfoundation.org> User-Agent: quilt/0.60-5.1.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3694 Lines: 102 3.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Matt Fleming commit ec50bd32f1672d38ddce10fb1841cbfda89cfe9a upstream. It's not wise to assume VariableNameSize represents the length of VariableName, as not all firmware updates VariableNameSize in the same way (some don't update it at all if EFI_SUCCESS is returned). There are even implementations out there that update VariableNameSize with values that are both larger than the string returned in VariableName and smaller than the buffer passed to GetNextVariableName(), which resulted in the following bug report from Michael Schroeder, > On HP z220 system (firmware version 1.54), some EFI variables are > incorrectly named : > > ls -d /sys/firmware/efi/vars/*8be4d* | grep -v -- -8be returns > /sys/firmware/efi/vars/dbxDefault-pport8be4df61-93ca-11d2-aa0d-00e098032b8c > /sys/firmware/efi/vars/KEKDefault-pport8be4df61-93ca-11d2-aa0d-00e098032b8c > /sys/firmware/efi/vars/SecureBoot-pport8be4df61-93ca-11d2-aa0d-00e098032b8c > /sys/firmware/efi/vars/SetupMode-Information8be4df61-93ca-11d2-aa0d-00e098032b8c The issue here is that because we blindly use VariableNameSize without verifying its value, we can potentially read garbage values from the buffer containing VariableName if VariableNameSize is larger than the length of VariableName. Since VariableName is a string, we can calculate its size by searching for the terminating NULL character. [Backported for 3.8-stable. Removed workqueue code added in a93bc0c 3.9-rc1.] Reported-by: Frederic Crozat Cc: Matthew Garrett Cc: Josh Boyer Cc: Michael Schroeder Cc: Lee, Chun-Yi Cc: Lingzhu Xiang Cc: Seiji Aguchi Signed-off-by: Matt Fleming Signed-off-by: Lingzhu Xiang Reviewed-by: CAI Qian Signed-off-by: Greg Kroah-Hartman --- drivers/firmware/efivars.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) --- a/drivers/firmware/efivars.c +++ b/drivers/firmware/efivars.c @@ -731,6 +731,31 @@ static ssize_t efivar_delete(struct file } /* + * Returns the size of variable_name, in bytes, including the + * terminating NULL character, or variable_name_size if no NULL + * character is found among the first variable_name_size bytes. + */ +static unsigned long var_name_strnsize(efi_char16_t *variable_name, + unsigned long variable_name_size) +{ + unsigned long len; + efi_char16_t c; + + /* + * The variable name is, by definition, a NULL-terminated + * string, so make absolutely sure that variable_name_size is + * the value we expect it to be. If not, return the real size. + */ + for (len = 2; len <= variable_name_size; len += sizeof(c)) { + c = variable_name[(len / sizeof(c)) - 1]; + if (!c) + break; + } + + return min(len, variable_name_size); +} + +/* * Let's not leave out systab information that snuck into * the efivars driver */ @@ -957,6 +982,8 @@ int register_efivars(struct efivars *efi &vendor_guid); switch (status) { case EFI_SUCCESS: + variable_name_size = var_name_strnsize(variable_name, + variable_name_size); efivar_create_sysfs_entry(efivars, variable_name_size, variable_name, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/