From: Zhen Lei <thunder.leizhen@huawei.com>
To: Ilya Dryomov <idryomov@gmail.com>,
Dongsheng Yang <dongsheng.yang@easystack.cn>,
Jens Axboe <axboe@kernel.dk>,
Yehuda Sadeh <yehuda@hq.newdream.net>,
Sage Weil <sage@newdream.net>,
ceph-devel <ceph-devel@vger.kernel.org>,
linux-block <linux-block@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Cc: Zhen Lei <thunder.leizhen@huawei.com>
Subject: [PATCH] rbd: use kref_put_lock() to fix potential UAF
Date: Thu, 22 Jul 2021 12:02:16 +0800 [thread overview]
Message-ID: <20210722040216.4090-1-thunder.leizhen@huawei.com> (raw)
When the refcount is decreased to 0, the rbd_client_release() is called.
Before CPU0 reaches the race point (1), CPU1 may obtain the spinlock
and traverse the linked list to find 'rbdc'. Although CPU1 will call
kref_get() to increase the refcount, it is obviously too late. CPU0 will
release 'rbdc' directly, CPU1 then accesses 'rbdc' and triggers UAF.
Use kref_put_lock() to ensure that both the operations of decrease
refcount to 0 and link deletion are lock protected eliminates this risk.
CPU0 CPU1
rbd_client_release():
<-------- (1)
spin_lock(&rbd_client_list_lock);
list_del(&rbdc->node);
spin_unlock(&rbd_client_list_lock);
kfree(rbdc);
<-------- use-after-free
Fixes: 602adf400201 ("rbd: introduce rados block device (rbd), based on libceph")
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
drivers/block/rbd.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 531d390902dd..3a8989bf8e9c 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -875,11 +875,11 @@ static void rbd_client_release(struct kref *kref)
{
struct rbd_client *rbdc = container_of(kref, struct rbd_client, kref);
- dout("%s: rbdc %p\n", __func__, rbdc);
- spin_lock(&rbd_client_list_lock);
list_del(&rbdc->node);
spin_unlock(&rbd_client_list_lock);
+ dout("%s: rbdc %p\n", __func__, rbdc);
+
ceph_destroy_client(rbdc->client);
kfree(rbdc);
}
@@ -891,7 +891,8 @@ static void rbd_client_release(struct kref *kref)
static void rbd_put_client(struct rbd_client *rbdc)
{
if (rbdc)
- kref_put(&rbdc->kref, rbd_client_release);
+ kref_put_lock(&rbdc->kref,
+ rbd_client_release, &rbd_client_list_lock);
}
/*
--
2.25.1
reply other threads:[~2021-07-22 4:03 UTC|newest]
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