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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org,
        "Martin Schwidefsky" <schwidefsky@de.ibm.com>,
        "Heiko Carstens" <heiko.carstens@de.ibm.com>,
        "Eugene Syromiatnikov" <esyr@redhat.com>
Date:   Thu, 07 Jun 2018 15:05:21 +0100
Message-ID: <lsq.1528380321.443712909@decadent.org.uk>
Subject: [PATCH 3.16 161/410] s390: fix handling of -1 in set{,fs}[gu]id16
 syscalls
In-Reply-To: <lsq.1528380320.647747352@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
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3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Eugene Syromiatnikov <esyr@redhat.com>

commit 6dd0d2d22aa363fec075cb2577ba273ac8462e94 upstream.

For some reason, the implementation of some 16-bit ID system calls
(namely, setuid16/setgid16 and setfsuid16/setfsgid16) used type cast
instead of low2highgid/low2highuid macros for converting [GU]IDs, which
led to incorrect handling of value of -1 (which ought to be considered
invalid).

Discovered by strace test suite.

Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 arch/s390/kernel/compat_linux.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/arch/s390/kernel/compat_linux.c
+++ b/arch/s390/kernel/compat_linux.c
@@ -110,7 +110,7 @@ COMPAT_SYSCALL_DEFINE2(s390_setregid16,
 
 COMPAT_SYSCALL_DEFINE1(s390_setgid16, u16, gid)
 {
-	return sys_setgid((gid_t)gid);
+	return sys_setgid(low2highgid(gid));
 }
 
 COMPAT_SYSCALL_DEFINE2(s390_setreuid16, u16, ruid, u16, euid)
@@ -120,7 +120,7 @@ COMPAT_SYSCALL_DEFINE2(s390_setreuid16,
 
 COMPAT_SYSCALL_DEFINE1(s390_setuid16, u16, uid)
 {
-	return sys_setuid((uid_t)uid);
+	return sys_setuid(low2highuid(uid));
 }
 
 COMPAT_SYSCALL_DEFINE3(s390_setresuid16, u16, ruid, u16, euid, u16, suid)
@@ -173,12 +173,12 @@ COMPAT_SYSCALL_DEFINE3(s390_getresgid16,
 
 COMPAT_SYSCALL_DEFINE1(s390_setfsuid16, u16, uid)
 {
-	return sys_setfsuid((uid_t)uid);
+	return sys_setfsuid(low2highuid(uid));
 }
 
 COMPAT_SYSCALL_DEFINE1(s390_setfsgid16, u16, gid)
 {
-	return sys_setfsgid((gid_t)gid);
+	return sys_setfsgid(low2highgid(gid));
 }
 
 static int groups16_to_user(u16 __user *grouplist, struct group_info *group_info)