linux-kernel - [PATCH] sysfs: tightened sysfs permission checks

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <1430482103-21248-1-git-send-email-gobinda.cemk07@gmail.com>
Date:	Fri,  1 May 2015 17:38:23 +0530
From:	Gobinda Charan Maji <gobinda.cemk07@...il.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Linux Next <linux-next@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH] sysfs: tightened sysfs permission checks

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 <gobinda.cemk07@...il.com>
---
 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@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/