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
PER_MASK bytes.
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@suse.cz>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/kernel/sys_s390.c b/arch/s390/kernel/sys_s390.c
index b4a29ee..d0964d2 100644 (file)
--- 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_LINUX32;
        ret = sys_personality(personality);
-       if (ret == PER_LINUX32)
-               ret = PER_LINUX;
+       if (personality(ret) == PER_LINUX32)
+               ret &= ~PER_LINUX32;
 
        return ret;
 }