[PATCH] secure unlock_task_sighand() call

[Ajeet Yadav]

Since the return value was not checked for lock_task_sighand(),
there was a chance that spin_unlock_irqrestore being called
from unlock_task_sighand gets called wihout actually acquire
the lock, which inturn can lead to kernel crash.

Signed-off-by: Ajeet Yadav <ajeet.yadav.77@xxxxxxxxx>
Signed-off-by: Vaibhav Shinde <v.bhav.shinde@xxxxxxxxx>

---
 fs/coredump.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index 6d8b4cd..447b02c 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -357,9 +357,10 @@ static inline int zap_threads(struct task_struct
*tsk, struct mm_struct *mm,
                do {
                        if (p->mm) {
                                if (unlikely(p->mm == mm)) {
-                                       lock_task_sighand(p, &flags);
-                                       nr += zap_process(p, exit_code);
-                                       unlock_task_sighand(p, &flags);
+                                       if (lock_task_sighand(p, &flags) {
+                                               nr += zap_process(p, exit_code);
+                                               unlock_task_sighand(p, &flags);
+                                       }
                                }
                                break;
                        }
--
1.7.9.5
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