pids: introduce find_get_task_by_vpid() helper

There are several functions that do find_task_by_vpid() followed by
get_task_struct().  We can use a helper function instead.

Link: http://lkml.kernel.org/r/1509602027-11337-1-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 21 insertions, 45 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index 7f719d1..1f450e0 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -862,24 +862,6 @@ static void put_pi_state(struct futex_pi_state *pi_state)
 	}
 }
 
-/*
- * Look up the task based on what TID userspace gave us.
- * We dont trust it.
- */
-static struct task_struct *futex_find_get_task(pid_t pid)
-{
-	struct task_struct *p;
-
-	rcu_read_lock();
-	p = find_task_by_vpid(pid);
-	if (p)
-		get_task_struct(p);
-
-	rcu_read_unlock();
-
-	return p;
-}
-
 #ifdef CONFIG_FUTEX_PI
 
 /*
@@ -1183,7 +1165,7 @@ static int attach_to_pi_owner(u32 uval, union futex_key *key,
 	 */
 	if (!pid)
 		return -ESRCH;
-	p = futex_find_get_task(pid);
+	p = find_get_task_by_vpid(pid);
 	if (!p)
 		return -ESRCH;
 
diff --git a/kernel/pid.c b/kernel/pid.c
index 5d30c87..ed6c343 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -343,6 +343,19 @@ struct task_struct *find_task_by_vpid(pid_t vnr)
 	return find_task_by_pid_ns(vnr, task_active_pid_ns(current));
 }
 
+struct task_struct *find_get_task_by_vpid(pid_t nr)
+{
+	struct task_struct *task;
+
+	rcu_read_lock();
+	task = find_task_by_vpid(nr);
+	if (task)
+		get_task_struct(task);
+	rcu_read_unlock();
+
+	return task;
+}
+
 struct pid *get_task_pid(struct task_struct *task, enum pid_type type)
 {
 	struct pid *pid;
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 5e1d713..21fec73 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -1103,21 +1103,6 @@ int ptrace_request(struct task_struct *child, long request,
 	return ret;
 }
 
-static struct task_struct *ptrace_get_task_struct(pid_t pid)
-{
-	struct task_struct *child;
-
-	rcu_read_lock();
-	child = find_task_by_vpid(pid);
-	if (child)
-		get_task_struct(child);
-	rcu_read_unlock();
-
-	if (!child)
-		return ERR_PTR(-ESRCH);
-	return child;
-}
-
 #ifndef arch_ptrace_attach
 #define arch_ptrace_attach(child)	do { } while (0)
 #endif
@@ -1135,9 +1120,9 @@ SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr,
 		goto out;
 	}
 
-	child = ptrace_get_task_struct(pid);
-	if (IS_ERR(child)) {
-		ret = PTR_ERR(child);
+	child = find_get_task_by_vpid(pid);
+	if (!child) {
+		ret = -ESRCH;
 		goto out;
 	}
 
@@ -1281,9 +1266,9 @@ COMPAT_SYSCALL_DEFINE4(ptrace, compat_long_t, request, compat_long_t, pid,
 		goto out;
 	}
 
-	child = ptrace_get_task_struct(pid);
-	if (IS_ERR(child)) {
-		ret = PTR_ERR(child);
+	child = find_get_task_by_vpid(pid);
+	if (!child) {
+		ret = -ESRCH;
 		goto out;
 	}
 
diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index 4559e91..4e62a4a 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -194,11 +194,7 @@ static int fill_stats_for_pid(pid_t pid, struct taskstats *stats)
 {
 	struct task_struct *tsk;
 
-	rcu_read_lock();
-	tsk = find_task_by_vpid(pid);
-	if (tsk)
-		get_task_struct(tsk);
-	rcu_read_unlock();
+	tsk = find_get_task_by_vpid(pid);
 	if (!tsk)
 		return -ESRCH;
 	fill_stats(current_user_ns(), task_active_pid_ns(current), tsk, stats);