[PATCH v3] pids: introduce find_get_task_by_vpid helper
From: Mike Rapoport
Date: Thu Nov 02 2017 - 01:54:05 EST
There are several functions that do find_task_by_vpid() followed by
get_task_struct(). We can use a helper function instead.
Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---
v3: update arch/ia64/kernel/perfmon.c and security/yama/yama_lsm.c that
were missing in the previous versions
v2: remove futex_find_get_task() and ptrace_get_task_struct() as Oleg
suggested
arch/ia64/kernel/perfmon.c | 13 +++----------
include/linux/sched.h | 5 +++++
kernel/futex.c | 20 +-------------------
kernel/pid.c | 13 +++++++++++++
kernel/ptrace.c | 27 ++++++---------------------
kernel/taskstats.c | 6 +-----
mm/process_vm_access.c | 6 +-----
security/yama/yama_lsm.c | 11 +++--------
8 files changed, 33 insertions(+), 68 deletions(-)
diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c
index 09f86ebfcc7b..496b3f87ffab 100644
--- a/arch/ia64/kernel/perfmon.c
+++ b/arch/ia64/kernel/perfmon.c
@@ -2610,17 +2610,10 @@ pfm_get_task(pfm_context_t *ctx, pid_t pid, struct task_struct **task)
if (pid < 2) return -EPERM;
if (pid != task_pid_vnr(current)) {
-
- read_lock(&tasklist_lock);
-
- p = find_task_by_vpid(pid);
-
/* make sure task cannot go away while we operate on it */
- if (p) get_task_struct(p);
-
- read_unlock(&tasklist_lock);
-
- if (p == NULL) return -ESRCH;
+ p = find_get_task_by_vpid(pid);
+ if (!p)
+ return -ESRCH;
}
ret = pfm_task_incompatible(ctx, p);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 26a7df4e558c..4c3af5255fcf 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1484,6 +1484,11 @@ static inline struct thread_info *task_thread_info(struct task_struct *task)
extern struct task_struct *find_task_by_vpid(pid_t nr);
extern struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns);
+/*
+ * find a task by its virtual pid and get the task struct
+ */
+extern struct task_struct *find_get_task_by_vpid(pid_t nr);
+
extern int wake_up_state(struct task_struct *tsk, unsigned int state);
extern int wake_up_process(struct task_struct *tsk);
extern void wake_up_new_task(struct task_struct *tsk);
diff --git a/kernel/futex.c b/kernel/futex.c
index 0518a0bfc746..e2a160549a0c 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
/*
@@ -1166,7 +1148,7 @@ 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 020dedbdf066..ead086b0ef8e 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -462,6 +462,19 @@ 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 84b1367935e4..6f3de14313f5 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -1099,21 +1099,6 @@ 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
@@ -1131,9 +1116,9 @@ 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;
}
@@ -1278,9 +1263,9 @@ 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 4559e914452b..4e62a4a8fa91 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);
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
index 8973cd231ece..16424b9ae424 100644
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -197,11 +197,7 @@ static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter,
}
/* Get process information */
- rcu_read_lock();
- task = find_task_by_vpid(pid);
- if (task)
- get_task_struct(task);
- rcu_read_unlock();
+ task = find_get_task_by_vpid(pid);
if (!task) {
rc = -ESRCH;
goto free_proc_pages;
diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index 8298e094f4f7..ffda91a4a1aa 100644
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -250,15 +250,10 @@ int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
} else {
struct task_struct *tracer;
- rcu_read_lock();
- tracer = find_task_by_vpid(arg2);
- if (tracer)
- get_task_struct(tracer);
- else
+ tracer = find_get_task_by_vpid(arg2);
+ if (!tracer) {
rc = -EINVAL;
- rcu_read_unlock();
-
- if (tracer) {
+ } else {
rc = yama_ptracer_add(tracer, myself);
put_task_struct(tracer);
}
--
2.7.4