linux-kernel - [PATCH] [S390] do not clobber personality flags in sys_32

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Message-ID: <alpine.LNX.2.00.1208012045500.14910@pobox.suse.cz>
Date:	Wed, 1 Aug 2012 20:48:48 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	linux390@...ibm.com, linux-s390@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] [S390] do not clobber personality flags in
 sys_32_personality()

There are multiple errors in how sys_32_personality() handles personality
flags stored in top three bytes.

- directly comparing current->personality against PER_LINUX32 doesn't work
  in cases when any of the personality flags stored in the top three bytes
  are used.
- directly forcefully setting personality to PER_LINUX32 or PER_LINUX
  discards any flags stored in the top three bytes

Fix the first one by properly using personality() macro to compare only
bytes covered by PER_MASK.
Fix the second one by setting only the bits that should be set, instead of
overwriting the whole value.

Signed-off-by: Jiri Kosina <jkosina@...e.cz>
---
 arch/s390/kernel/sys_s390.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/s390/kernel/sys_s390.c b/arch/s390/kernel/sys_s390.c
index b4a29ee..6afcfd9 100644
--- a/arch/s390/kernel/sys_s390.c
+++ b/arch/s390/kernel/sys_s390.c
@@ -81,11 +81,12 @@ SYSCALL_DEFINE1(s390_personality, unsigned int, personality)
 {
 	unsigned int ret;
 
-	if (current->personality == PER_LINUX32 && personality == PER_LINUX)
-		personality = PER_LINUX32;
+	if (personality(current->personality) == PER_LINUX32 &&
+	    personality(personality) == PER_LINUX)
+		personality &= ~PER_LINUX | PER_LINUX32;
 	ret = sys_personality(personality);
-	if (ret == PER_LINUX32)
-		ret = PER_LINUX;
+	if (personality(ret) == PER_LINUX32)
+		ret &= ~PER_LINUX32 | PER_LINUX;
 
 	return ret;
 }

-- 
Jiri Kosina
SUSE Labs
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