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Subject[PATCH v2] s390: fix handling of -1 in set{,fs}[gu]id16 syscalls
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>
---
arch/s390/kernel/compat_linux.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/s390/kernel/compat_linux.c b/arch/s390/kernel/compat_linux.c
index f04db37..9ba2ab2 100644
--- a/arch/s390/kernel/compat_linux.c
+++ b/arch/s390/kernel/compat_linux.c
@@ -110,7 +110,7 @@ COMPAT_SYSCALL_DEFINE2(s390_setregid16, u16, rgid, u16, egid)

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, u16, ruid, u16, euid)

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, u16 __user *, rgidp,

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)
--
2.9.3
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