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, 52 insertions, 32 deletions

diff --git a/ipc/sem.c b/ipc/sem.c
index 971e75d28364..ae8d9104b0a0 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -1984,46 +1984,34 @@ out:
 	return un;
 }
 
-static long do_semtimedop(int semid, struct sembuf __user *tsops,
-		unsigned nsops, const struct timespec64 *timeout)
+long __do_semtimedop(int semid, struct sembuf *sops,
+		unsigned nsops, const struct timespec64 *timeout,
+		struct ipc_namespace *ns)
 {
 	int error = -EINVAL;
 	struct sem_array *sma;
-	struct sembuf fast_sops[SEMOPM_FAST];
-	struct sembuf *sops = fast_sops, *sop;
+	struct sembuf *sop;
 	struct sem_undo *un;
 	int max, locknum;
 	bool undos = false, alter = false, dupsop = false;
 	struct sem_queue queue;
 	unsigned long dup = 0, jiffies_left = 0;
-	struct ipc_namespace *ns;
-
-	ns = current->nsproxy->ipc_ns;
 
 	if (nsops < 1 || semid < 0)
 		return -EINVAL;
 	if (nsops > ns->sc_semopm)
 		return -E2BIG;
-	if (nsops > SEMOPM_FAST) {
-		sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL);
-		if (sops == NULL)
-			return -ENOMEM;
-	}
-
-	if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
-		error =  -EFAULT;
-		goto out_free;
-	}
 
 	if (timeout) {
 		if (timeout->tv_sec < 0 || timeout->tv_nsec < 0 ||
 			timeout->tv_nsec >= 1000000000L) {
 			error = -EINVAL;
-			goto out_free;
+			goto out;
 		}
 		jiffies_left = timespec64_to_jiffies(timeout);
 	}
 
+
 	max = 0;
 	for (sop = sops; sop < sops + nsops; sop++) {
 		unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG);
@@ -2052,7 +2040,7 @@ static long do_semtimedop(int semid, struct sembuf __user *tsops,
 		un = find_alloc_undo(ns, semid);
 		if (IS_ERR(un)) {
 			error = PTR_ERR(un);
-			goto out_free;
+			goto out;
 		}
 	} else {
 		un = NULL;
@@ -2063,25 +2051,25 @@ static long do_semtimedop(int semid, struct sembuf __user *tsops,
 	if (IS_ERR(sma)) {
 		rcu_read_unlock();
 		error = PTR_ERR(sma);
-		goto out_free;
+		goto out;
 	}
 
 	error = -EFBIG;
 	if (max >= sma->sem_nsems) {
 		rcu_read_unlock();
-		goto out_free;
+		goto out;
 	}
 
 	error = -EACCES;
 	if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) {
 		rcu_read_unlock();
-		goto out_free;
+		goto out;
 	}
 
 	error = security_sem_semop(&sma->sem_perm, sops, nsops, alter);
 	if (error) {
 		rcu_read_unlock();
-		goto out_free;
+		goto out;
 	}
 
 	error = -EIDRM;
@@ -2095,7 +2083,7 @@ static long do_semtimedop(int semid, struct sembuf __user *tsops,
 	 * entangled here and why it's RMID race safe on comments at sem_lock()
 	 */
 	if (!ipc_valid_object(&sma->sem_perm))
-		goto out_unlock_free;
+		goto out_unlock;
 	/*
 	 * semid identifiers are not unique - find_alloc_undo may have
 	 * allocated an undo structure, it was invalidated by an RMID
@@ -2104,7 +2092,7 @@ static long do_semtimedop(int semid, struct sembuf __user *tsops,
 	 * "un" itself is guaranteed by rcu.
 	 */
 	if (un && un->semid == -1)
-		goto out_unlock_free;
+		goto out_unlock;
 
 	queue.sops = sops;
 	queue.nsops = nsops;
@@ -2130,10 +2118,10 @@ static long do_semtimedop(int semid, struct sembuf __user *tsops,
 		rcu_read_unlock();
 		wake_up_q(&wake_q);
 
-		goto out_free;
+		goto out;
 	}
 	if (error < 0) /* non-blocking error path */
-		goto out_unlock_free;
+		goto out_unlock;
 
 	/*
 	 * We need to sleep on this operation, so we put the current
@@ -2198,14 +2186,14 @@ static long do_semtimedop(int semid, struct sembuf __user *tsops,
 		if (error != -EINTR) {
 			/* see SEM_BARRIER_2 for purpose/pairing */
 			smp_acquire__after_ctrl_dep();
-			goto out_free;
+			goto out;
 		}
 
 		rcu_read_lock();
 		locknum = sem_lock(sma, sops, nsops);
 
 		if (!ipc_valid_object(&sma->sem_perm))
-			goto out_unlock_free;
+			goto out_unlock;
 
 		/*
 		 * No necessity for any barrier: We are protect by sem_lock()
@@ -2217,7 +2205,7 @@ static long do_semtimedop(int semid, struct sembuf __user *tsops,
 		 * Leave without unlink_queue(), but with sem_unlock().
 		 */
 		if (error != -EINTR)
-			goto out_unlock_free;
+			goto out_unlock;
 
 		/*
 		 * If an interrupt occurred we have to clean up the queue.
@@ -2228,13 +2216,45 @@ static long do_semtimedop(int semid, struct sembuf __user *tsops,
 
 	unlink_queue(sma, &queue);
 
-out_unlock_free:
+out_unlock:
 	sem_unlock(sma, locknum);
 	rcu_read_unlock();
+out:
+	return error;
+}
+
+static long do_semtimedop(int semid, struct sembuf __user *tsops,
+		unsigned nsops, const struct timespec64 *timeout)
+{
+	struct sembuf fast_sops[SEMOPM_FAST];
+	struct sembuf *sops = fast_sops;
+	struct ipc_namespace *ns;
+	int ret;
+
+	ns = current->nsproxy->ipc_ns;
+	if (nsops > ns->sc_semopm)
+		return -E2BIG;
+	if (nsops < 1)
+		return -EINVAL;
+
+	if (nsops > SEMOPM_FAST) {
+		sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL);
+		if (sops == NULL)
+			return -ENOMEM;
+	}
+
+	if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
+		ret =  -EFAULT;
+		goto out_free;
+	}
+
+	ret = __do_semtimedop(semid, sops, nsops, timeout, ns);
+
 out_free:
 	if (sops != fast_sops)
 		kvfree(sops);
-	return error;
+
+	return ret;
 }
 
 long ksys_semtimedop(int semid, struct sembuf __user *tsops,