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From:   Daniel Jordan <daniel.m.jordan@oracle.com>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Sasha Levin <sashal@kernel.org>
Cc:     Daniel Jordan <daniel.m.jordan@oracle.com>,
        Yang Yingliang <yangyingliang@huawei.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Steffen Klassert <steffen.klassert@secunet.com>,
        linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: [PATCH for 4.19-stable] padata: fix null pointer deref of pd->pinst
Date:   Fri, 14 Feb 2020 13:28:21 -0500
Message-Id: <20200214182821.337706-1-daniel.m.jordan@oracle.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

The 4.19 backport dc34710a7aba ("padata: Remove broken queue flushing")
removed padata_alloc_pd()'s assignment to pd->pinst, resulting in:

    Unable to handle kernel NULL pointer dereference ...
    ...
    pc : padata_reorder+0x144/0x2e0
    ...
    Call trace:
     padata_reorder+0x144/0x2e0
     padata_do_serial+0xc8/0x128
     pcrypt_aead_enc+0x60/0x70 [pcrypt]
     padata_parallel_worker+0xd8/0x138
     process_one_work+0x1bc/0x4b8
     worker_thread+0x164/0x580
     kthread+0x134/0x138
     ret_from_fork+0x10/0x18

This happened because the backport was based on an enhancement that
moved this assignment but isn't in 4.19:

  bfde23ce200e ("padata: unbind parallel jobs from specific CPUs")

Simply restore the assignment to fix the crash.

Fixes: dc34710a7aba ("padata: Remove broken queue flushing")
Reported-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
---
 kernel/padata.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/padata.c b/kernel/padata.c
index 11c5f9c8779e..cfab62923c45 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -510,6 +510,7 @@ static struct parallel_data *padata_alloc_pd(struct padata_instance *pinst,
 	atomic_set(&pd->seq_nr, -1);
 	atomic_set(&pd->reorder_objects, 0);
 	atomic_set(&pd->refcnt, 1);
+	pd->pinst = pinst;
 	spin_lock_init(&pd->lock);
 
 	return pd;
-- 
2.25.0