[PATCH 4.15 026/163] s390: fix handling of -1 in set{,fs}[gu]id16 syscalls

Greg Kroah-Hartman
2018-02-21T12:47:35Z

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.

Cc: stable@vger.kernel.org
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
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)