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SubjectRe: [syzbot] [net?] [virt?] [kvm?] KASAN: slab-use-after-free Read in vhost_task_fn
Date
please test uaf in vhost_task_fn

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git bb7a2467e6be

diff --git a/kernel/softirq.c b/kernel/softirq.c
index b315b21fb28c..02582017759a 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -508,7 +508,7 @@ static inline bool lockdep_softirq_start(void) { return false; }
static inline void lockdep_softirq_end(bool in_hardirq) { }
#endif

-asmlinkage __visible void __softirq_entry __do_softirq(void)
+static void handle_softirqs(bool ksirqd)
{
unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
unsigned long old_flags = current->flags;
@@ -563,8 +563,7 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
pending >>= softirq_bit;
}

- if (!IS_ENABLED(CONFIG_PREEMPT_RT) &&
- __this_cpu_read(ksoftirqd) == current)
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT) && ksirqd)
rcu_softirq_qs();

local_irq_disable();
@@ -584,6 +583,11 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
current_restore_flags(old_flags, PF_MEMALLOC);
}

+asmlinkage __visible void __softirq_entry __do_softirq(void)
+{
+ handle_softirqs(false);
+}
+
/**
* irq_enter_rcu - Enter an interrupt context with RCU watching
*/
@@ -921,7 +925,7 @@ static void run_ksoftirqd(unsigned int cpu)
* We can safely run softirq on inline stack, as we are not deep
* in the task stack here.
*/
- __do_softirq();
+ handle_softirqs(true);
ksoftirqd_run_end();
cond_resched();
return;
diff --git a/kernel/vhost_task.c b/kernel/vhost_task.c
index 48c289947b99..8800f5acc007 100644
--- a/kernel/vhost_task.c
+++ b/kernel/vhost_task.c
@@ -61,8 +61,8 @@ static int vhost_task_fn(void *data)
set_bit(VHOST_TASK_FLAGS_KILLED, &vtsk->flags);
vtsk->handle_sigkill(vtsk->data);
}
- complete(&vtsk->exited);
mutex_unlock(&vtsk->exit_mutex);
+ complete(&vtsk->exited);

do_exit(0);
}

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