Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753791AbbEAMIb (ORCPT ); Fri, 1 May 2015 08:08:31 -0400 Received: from mail-pd0-f178.google.com ([209.85.192.178]:33338 "EHLO mail-pd0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753730AbbEAMI3 (ORCPT ); Fri, 1 May 2015 08:08:29 -0400 From: Gobinda Charan Maji To: Rusty Russell Cc: Linux Next , Linux Kernel Subject: [PATCH] sysfs: tightened sysfs permission checks Date: Fri, 1 May 2015 17:38:23 +0530 Message-Id: <1430482103-21248-1-git-send-email-gobinda.cemk07@gmail.com> X-Mailer: git-send-email 1.8.1.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2414 Lines: 54 There were some inconsistency in restriction to VERIFY_OCTAL_PERMISSIONS(). Previously the test was "User perms >= group perms >= other perms". The permission field of User, Group or Other consists of three bits. LSB is EXECUTE permission, MSB is READ permission and the middle bit is WRITE permission. But logically WRITE is "more privileged" than READ. Say for example, permission value is "0430". Here User has only READ permission whereas Group has both WRITE and EXECUTE permission. So, the checks could be tightened and the tests are separated to USER_READABLE >= GROUP_READABLE >= OTHER_READABLE, USER_WRITABLE >= GROUP_WRITABLE and OTHER_WRITABLE is not permitted. Signed-off-by: Gobinda Charan Maji --- include/linux/kernel.h | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 3a5b48e..cd54b35 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -818,13 +818,15 @@ static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { } #endif /* Permissions on a sysfs file: you didn't miss the 0 prefix did you? */ -#define VERIFY_OCTAL_PERMISSIONS(perms) \ - (BUILD_BUG_ON_ZERO((perms) < 0) + \ - BUILD_BUG_ON_ZERO((perms) > 0777) + \ - /* User perms >= group perms >= other perms */ \ - BUILD_BUG_ON_ZERO(((perms) >> 6) < (((perms) >> 3) & 7)) + \ - BUILD_BUG_ON_ZERO((((perms) >> 3) & 7) < ((perms) & 7)) + \ - /* Other writable? Generally considered a bad idea. */ \ - BUILD_BUG_ON_ZERO((perms) & 2) + \ +#define VERIFY_OCTAL_PERMISSIONS(perms) \ + (BUILD_BUG_ON_ZERO((perms) < 0) + \ + BUILD_BUG_ON_ZERO((perms) > 0777) + \ + /* USER_READABLE >= GROUP_READABLE >= OTHER_READABLE */ \ + BUILD_BUG_ON_ZERO((((perms) >> 6) & 4) < (((perms) >> 3) & 4)) + \ + BUILD_BUG_ON_ZERO((((perms) >> 3) & 4) < ((perms) & 4)) + \ + /* USER_WRITABLE >= GROUP_WRITABLE */ \ + BUILD_BUG_ON_ZERO((((perms) >> 6) & 2) < (((perms) >> 3) & 2)) + \ + /* OTHER_WRITABLE? Generally considered a bad idea. */ \ + BUILD_BUG_ON_ZERO((perms) & 2) + \ (perms)) #endif -- 1.8.1.4 -- 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/