ptrace: don't take tasklist to get/set ->last_siginfo

Change ptrace_getsiginfo/ptrace_setsiginfo to use lock_task_sighand()
without tasklist_lock.  Perhaps it makes sense to make a single helper
with "bool rw" argument.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 10 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index a64fe75a48b..61c78b2c07b 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -424,37 +424,33 @@ static int ptrace_setoptions(struct task_struct *child, long data)
 
 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
 {
+        unsigned long flags;
         int error = -ESRCH;
 
-        read_lock(&tasklist_lock);
-        if (likely(child->sighand != NULL)) {
+        if (lock_task_sighand(child, &flags)) {
                 error = -EINVAL;
-                spin_lock_irq(&child->sighand->siglock);
                 if (likely(child->last_siginfo != NULL)) {
                         *info = *child->last_siginfo;
                         error = 0;
                 }
-                spin_unlock_irq(&child->sighand->siglock);
+                unlock_task_sighand(child, &flags);
         }
-        read_unlock(&tasklist_lock);
         return error;
 }
 
 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
 {
+        unsigned long flags;
         int error = -ESRCH;
 
-        read_lock(&tasklist_lock);
-        if (likely(child->sighand != NULL)) {
+        if (lock_task_sighand(child, &flags)) {
                 error = -EINVAL;
-                spin_lock_irq(&child->sighand->siglock);
                 if (likely(child->last_siginfo != NULL)) {
                         *child->last_siginfo = *info;
                         error = 0;
                 }
-                spin_unlock_irq(&child->sighand->siglock);
+                unlock_task_sighand(child, &flags);
         }
-        read_unlock(&tasklist_lock);
         return error;
 }