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authorPaul E. McKenney <paulmck@linux.ibm.com>2019-02-12 21:44:33 +0300
committerPaul E. McKenney <paulmck@linux.ibm.com>2019-03-27 00:39:24 +0300
commit5cdfd174ea6c2dc1d331b61bdc9572698658600a (patch)
treee038dc46ffae28bfda548887b93056e6a5741afb /kernel/rcu/srcutree.c
parent9e98c678c2d6ae3a17cb2de55d17f69dddaa231b (diff)
downloadlinux-5cdfd174ea6c2dc1d331b61bdc9572698658600a.tar.xz
srcu: Check for in-flight callbacks in _cleanup_srcu_struct()
If someone fails to drain the corresponding SRCU callbacks (for example, by failing to invoke srcu_barrier()) before invoking either cleanup_srcu_struct() or cleanup_srcu_struct_quiesced(), the resulting diagnostic is an ambiguous use-after-free diagnostic, and even then only if you are running something like KASAN. This commit therefore improves SRCU diagnostics by adding checks for in-flight callbacks at _cleanup_srcu_struct() time. Note that these diagnostics can still be defeated, for example, by invoking call_srcu() concurrently with cleanup_srcu_struct(). Which is a really bad idea, but sometimes all too easy to do. But even then, these diagnostics have at least some probability of catching the problem. Reported-by: Sagi Grimberg <sagi@grimberg.me> Reported-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Tested-by: Bart Van Assche <bvanassche@acm.org>
Diffstat (limited to 'kernel/rcu/srcutree.c')
-rw-r--r--kernel/rcu/srcutree.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index a60b8ba9e1ac..4f30f3ecabc1 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -387,6 +387,8 @@ void _cleanup_srcu_struct(struct srcu_struct *ssp, bool quiesced)
del_timer_sync(&sdp->delay_work);
flush_work(&sdp->work);
}
+ if (WARN_ON(rcu_segcblist_n_cbs(&sdp->srcu_cblist)))
+ return; /* Forgot srcu_barrier(), so just leak it! */
}
if (WARN_ON(rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) != SRCU_STATE_IDLE) ||
WARN_ON(srcu_readers_active(ssp))) {