[patch] sched: signedness bug in yield_to()

[patch] sched: signedness bug in yield_to()

[Dan Carpenter]

In 7b270f6099 "sched: Bail out of yield_to when source and target
runqueue has one task" we changed this to store -ESRCH so it needs to
be signed.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 3e7b280..7ba7ea5 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4384,7 +4384,7 @@ bool __sched yield_to(struct task_struct *p, bool preempt)
 	struct task_struct *curr = current;
 	struct rq *rq, *p_rq;
 	unsigned long flags;
-	bool yielded = 0;
+	int yielded = 0;
 
 	local_irq_save(flags);
 	rq = this_rq();

[patch] sched: signedness bug in yield_to()

[Dan Carpenter]

yield_to() is supposed to return -ESRCH if there is no task to
yield to, but because the type is bool that is the same as returning
true.

The only place I see which cares is kvm_vcpu_on_spin().

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9112646..7c72b14 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2173,7 +2173,7 @@ static inline void sched_autogroup_fork(struct signal_struct *sig) { }
 static inline void sched_autogroup_exit(struct signal_struct *sig) { }
 #endif
 
-extern bool yield_to(struct task_struct *p, bool preempt);
+extern int yield_to(struct task_struct *p, bool preempt);
 extern void set_user_nice(struct task_struct *p, long nice);
 extern int task_prio(const struct task_struct *p);
 /**
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 927fa33..40f8de4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4209,7 +4209,7 @@ EXPORT_SYMBOL(yield);
  *	false (0) if we failed to boost the target.
  *	-ESRCH if there's no task to yield to.
  */
-bool __sched yield_to(struct task_struct *p, bool preempt)
+int __sched yield_to(struct task_struct *p, bool preempt)
 {
 	struct task_struct *curr = current;
 	struct rq *rq, *p_rq;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 970c681..ec4e3bd 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -586,7 +586,7 @@ void mark_page_dirty(struct kvm *kvm, gfn_t gfn);
 
 void kvm_vcpu_block(struct kvm_vcpu *vcpu);
 void kvm_vcpu_kick(struct kvm_vcpu *vcpu);
-bool kvm_vcpu_yield_to(struct kvm_vcpu *target);
+int kvm_vcpu_yield_to(struct kvm_vcpu *target);
 void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu);
 void kvm_load_guest_fpu(struct kvm_vcpu *vcpu);
 void kvm_put_guest_fpu(struct kvm_vcpu *vcpu);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 95b4c2b..9458196 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1713,11 +1713,11 @@ void kvm_vcpu_kick(struct kvm_vcpu *vcpu)
 EXPORT_SYMBOL_GPL(kvm_vcpu_kick);
 #endif /* !CONFIG_S390 */
 
-bool kvm_vcpu_yield_to(struct kvm_vcpu *target)
+int kvm_vcpu_yield_to(struct kvm_vcpu *target)
 {
 	struct pid *pid;
 	struct task_struct *task = NULL;
-	bool ret = false;
+	int ret = 0;
 
 	rcu_read_lock();
 	pid = rcu_dereference(target->pid);

Re: [patch] sched: signedness bug in yield_to()

[Peter Zijlstra]

[-- Attachment #1: Type: text/plain, Size: 352 bytes --]

On Fri, May 23, 2014 at 01:20:42PM +0300, Dan Carpenter wrote:
> yield_to() is supposed to return -ESRCH if there is no task to
> yield to, but because the type is bool that is the same as returning
> true.
> 
> The only place I see which cares is kvm_vcpu_on_spin().
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Thanks Dan!

[-- Attachment #2: Type: application/pgp-signature, Size: 836 bytes --]

Re: [patch] sched: signedness bug in yield_to()

[Raghavendra KT]

On Fri, May 23, 2014 at 3:50 PM, Dan Carpenter <dan.carpenter@oracle.com> wrote:
> yield_to() is supposed to return -ESRCH if there is no task to
> yield to, but because the type is bool that is the same as returning
> true.
>
> The only place I see which cares is kvm_vcpu_on_spin().
>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Thanks,  Please feel free to add
Reviewed-by: Raghavendra <raghavendra.kt@linux.vnet.ibm.com>