ARM: 9114/1: oabi-compat: rework sys_semtimedop emulation

sys_oabi_semtimedop() is one of the last users of set_fs() on Arm. To
remove this one, expose the internal code of the actual implementation
that operates on a kernel pointer and call it directly after copying.

There should be no measurable impact on the normal execution of this
function, and it makes the overly long function a little shorter, which
may help readability.

While reworking the oabi version, make it behave a little more like
the native one, using kvmalloc_array() and restructure the code
flow in a similar way.

The naming of __do_semtimedop() is not very good, I hope someone can
come up with a better name.

One regression was spotted by kernel test robot <rong.a.chen@intel.com>
and fixed before the first mailing list submission.

Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

1 files changed, 44 insertions, 16 deletions

diff --git a/arch/arm/kernel/sys_oabi-compat.c b/arch/arm/kernel/sys_oabi-compat.c
index 1f6a433200f1..5ea365c35ca5 100644
--- a/arch/arm/kernel/sys_oabi-compat.c
+++ b/arch/arm/kernel/sys_oabi-compat.c
@@ -80,6 +80,7 @@
 #include <linux/socket.h>
 #include <linux/net.h>
 #include <linux/ipc.h>
+#include <linux/ipc_namespace.h>
 #include <linux/uaccess.h>
 #include <linux/slab.h>
 
@@ -302,46 +303,52 @@ struct oabi_sembuf {
 	unsigned short	__pad;
 };
 
+#define sc_semopm     sem_ctls[2]
+
+#ifdef CONFIG_SYSVIPC
 asmlinkage long sys_oabi_semtimedop(int semid,
 				    struct oabi_sembuf __user *tsops,
 				    unsigned nsops,
 				    const struct old_timespec32 __user *timeout)
 {
+	struct ipc_namespace *ns;
 	struct sembuf *sops;
-	struct old_timespec32 local_timeout;
 	long err;
 	int i;
 
+	ns = current->nsproxy->ipc_ns;
+	if (nsops > ns->sc_semopm)
+		return -E2BIG;
 	if (nsops < 1 || nsops > SEMOPM)
 		return -EINVAL;
-	if (!access_ok(tsops, sizeof(*tsops) * nsops))
-		return -EFAULT;
-	sops = kmalloc_array(nsops, sizeof(*sops), GFP_KERNEL);
+	sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL);
 	if (!sops)
 		return -ENOMEM;
 	err = 0;
 	for (i = 0; i < nsops; i++) {
 		struct oabi_sembuf osb;
-		err |= __copy_from_user(&osb, tsops, sizeof(osb));
+		err |= copy_from_user(&osb, tsops, sizeof(osb));
 		sops[i].sem_num = osb.sem_num;
 		sops[i].sem_op = osb.sem_op;
 		sops[i].sem_flg = osb.sem_flg;
 		tsops++;
 	}
-	if (timeout) {
-		/* copy this as well before changing domain protection */
-		err |= copy_from_user(&local_timeout, timeout, sizeof(*timeout));
-		timeout = &local_timeout;
-	}
 	if (err) {
 		err = -EFAULT;
-	} else {
-		mm_segment_t fs = get_fs();
-		set_fs(KERNEL_DS);
-		err = sys_semtimedop_time32(semid, sops, nsops, timeout);
-		set_fs(fs);
+		goto out;
+	}
+
+	if (timeout) {
+		struct timespec64 ts;
+		err = get_old_timespec32(&ts, timeout);
+		if (err)
+			goto out;
+		err = __do_semtimedop(semid, sops, nsops, &ts, ns);
+		goto out;
 	}
-	kfree(sops);
+	err = __do_semtimedop(semid, sops, nsops, NULL, ns);
+out:
+	kvfree(sops);
 	return err;
 }
 
@@ -368,6 +375,27 @@ asmlinkage int sys_oabi_ipc(uint call, int first, int second, int third,
 		return sys_ipc(call, first, second, third, ptr, fifth);
 	}
 }
+#else
+asmlinkage long sys_oabi_semtimedop(int semid,
+				    struct oabi_sembuf __user *tsops,
+				    unsigned nsops,
+				    const struct old_timespec32 __user *timeout)
+{
+	return -ENOSYS;
+}
+
+asmlinkage long sys_oabi_semop(int semid, struct oabi_sembuf __user *tsops,
+			       unsigned nsops)
+{
+	return -ENOSYS;
+}
+
+asmlinkage int sys_oabi_ipc(uint call, int first, int second, int third,
+			    void __user *ptr, long fifth)
+{
+	return -ENOSYS;
+}
+#endif
 
 asmlinkage long sys_oabi_bind(int fd, struct sockaddr __user *addr, int addrlen)
 {