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Commit f409adf5 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

futex: Protect pid lookup in compat code with RCU 



find_task_by_vpid() in compat_sys_get_robust_list() does not require
tasklist_lock. It can be protected with rcu_read_lock as done in
sys_get_robust_list() already.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Darren Hart <dvhltc@us.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
parent 2b876f95

kernel/futex_compat.c

+3 −3
Original line number Diff line number Diff line
@@ -146,7 +146,7 @@ compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr, 
		struct task_struct *p;



		ret = -ESRCH;

		read_lock(&tasklist_lock);

		rcu_read_lock();

		p = find_task_by_vpid(pid);

		if (!p)

			goto err_unlock;
@@ -157,7 +157,7 @@ compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr, 
		    !capable(CAP_SYS_PTRACE))

			goto err_unlock;

		head = p->compat_robust_list;

		read_unlock(&tasklist_lock);

		rcu_read_unlock();

	}



	if (put_user(sizeof(*head), len_ptr))
@@ -165,7 +165,7 @@ compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr, 
	return put_user(ptr_to_compat(head), head_ptr);



err_unlock:

	read_unlock(&tasklist_lock);

	rcu_read_unlock();



	return ret;

}