1 files changed, 21 insertions, 38 deletions

diff --git a/kernel/kcmp.c b/kernel/kcmp.c
index a0e3d7a0e8b8..5353edfad8e1 100644
--- a/kernel/kcmp.c
+++ b/kernel/kcmp.c
@@ -61,39 +61,34 @@ static int kcmp_ptr(void *v1, void *v2, enum kcmp_type type)
 static struct file *
 get_file_raw_ptr(struct task_struct *task, unsigned int idx)
 {
-	struct file *file = NULL;
+	struct file *file;
 
-	task_lock(task);
 	rcu_read_lock();
-
-	if (task->files)
-		file = fcheck_files(task->files, idx);
-
+	file = task_lookup_fd_rcu(task, idx);
 	rcu_read_unlock();
-	task_unlock(task);
 
 	return file;
 }
 
-static void kcmp_unlock(struct mutex *m1, struct mutex *m2)
+static void kcmp_unlock(struct rw_semaphore *l1, struct rw_semaphore *l2)
 {
-	if (likely(m2 != m1))
-		mutex_unlock(m2);
-	mutex_unlock(m1);
+	if (likely(l2 != l1))
+		up_read(l2);
+	up_read(l1);
 }
 
-static int kcmp_lock(struct mutex *m1, struct mutex *m2)
+static int kcmp_lock(struct rw_semaphore *l1, struct rw_semaphore *l2)
 {
 	int err;
 
-	if (m2 > m1)
-		swap(m1, m2);
+	if (l2 > l1)
+		swap(l1, l2);
 
-	err = mutex_lock_killable(m1);
-	if (!err && likely(m1 != m2)) {
-		err = mutex_lock_killable_nested(m2, SINGLE_DEPTH_NESTING);
+	err = down_read_killable(l1);
+	if (!err && likely(l1 != l2)) {
+		err = down_read_killable_nested(l2, SINGLE_DEPTH_NESTING);
 		if (err)
-			mutex_unlock(m1);
+			up_read(l1);
 	}
 
 	return err;
@@ -107,7 +102,6 @@ static int kcmp_epoll_target(struct task_struct *task1,
 {
 	struct file *filp, *filp_epoll, *filp_tgt;
 	struct kcmp_epoll_slot slot;
-	struct files_struct *files;
 
 	if (copy_from_user(&slot, uslot, sizeof(slot)))
 		return -EFAULT;
@@ -116,23 +110,12 @@ static int kcmp_epoll_target(struct task_struct *task1,
 	if (!filp)
 		return -EBADF;
 
-	files = get_files_struct(task2);
-	if (!files)
+	filp_epoll = fget_task(task2, slot.efd);
+	if (!filp_epoll)
 		return -EBADF;
 
-	spin_lock(&files->file_lock);
-	filp_epoll = fcheck_files(files, slot.efd);
-	if (filp_epoll)
-		get_file(filp_epoll);
-	else
-		filp_tgt = ERR_PTR(-EBADF);
-	spin_unlock(&files->file_lock);
-	put_files_struct(files);
-
-	if (filp_epoll) {
-		filp_tgt = get_epoll_tfile_raw_ptr(filp_epoll, slot.tfd, slot.toff);
-		fput(filp_epoll);
-	}
+	filp_tgt = get_epoll_tfile_raw_ptr(filp_epoll, slot.tfd, slot.toff);
+	fput(filp_epoll);
 
 	if (IS_ERR(filp_tgt))
 		return PTR_ERR(filp_tgt);
@@ -173,8 +156,8 @@ SYSCALL_DEFINE5(kcmp, pid_t, pid1, pid_t, pid2, int, type,
 	/*
 	 * One should have enough rights to inspect task details.
 	 */
-	ret = kcmp_lock(&task1->signal->cred_guard_mutex,
-			&task2->signal->cred_guard_mutex);
+	ret = kcmp_lock(&task1->signal->exec_update_lock,
+			&task2->signal->exec_update_lock);
 	if (ret)
 		goto err;
 	if (!ptrace_may_access(task1, PTRACE_MODE_READ_REALCREDS) ||
@@ -229,8 +212,8 @@ SYSCALL_DEFINE5(kcmp, pid_t, pid1, pid_t, pid2, int, type,
 	}
 
 err_unlock:
-	kcmp_unlock(&task1->signal->cred_guard_mutex,
-		    &task2->signal->cred_guard_mutex);
+	kcmp_unlock(&task1->signal->exec_update_lock,
+		    &task2->signal->exec_update_lock);
 err:
 	put_task_struct(task1);
 	put_task_struct(task2);