linux-kernel - [PATCH v2] crypto: pcrypt: Fix possible deadlock in padata_sysfs

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Message-ID: <20190601092332.136481-1-wangkefeng.wang@huawei.com>
Date:   Sat, 1 Jun 2019 17:23:32 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>
CC:     <linuxcrypto@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Hulk Robot <hulkci@...wei.com>
Subject: [PATCH v2] crypto: pcrypt: Fix possible deadlock in padata_sysfs_release

There is a deadlock issue in pcrypt_init_padata(),

pcrypt_init_padata()
    cpus_read_lock()
      padata_free()
        padata_sysfs_release()
          cpus_read_lock()

Narrow rcu_read_lock/unlock() and move put_online_cpus()
before padata_free() to fix it.

Reported-by: Hulk Robot <hulkci@...wei.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
---
 crypto/pcrypt.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/crypto/pcrypt.c b/crypto/pcrypt.c
index 0e9ce329fd47..f3dacb714cd4 100644
--- a/crypto/pcrypt.c
+++ b/crypto/pcrypt.c
@@ -407,16 +407,19 @@ static int pcrypt_init_padata(struct padata_pcrypt *pcrypt,
 	int ret = -ENOMEM;
 	struct pcrypt_cpumask *mask;
 
-	get_online_cpus();
 
 	pcrypt->wq = alloc_workqueue("%s", WQ_MEM_RECLAIM | WQ_CPU_INTENSIVE,
 				     1, name);
 	if (!pcrypt->wq)
 		goto err;
 
+	get_online_cpus();
+
 	pcrypt->pinst = padata_alloc_possible(pcrypt->wq);
-	if (!pcrypt->pinst)
+	if (!pcrypt->pinst) {
+		put_online_cpus();
 		goto err_destroy_workqueue;
+	}
 
 	mask = kmalloc(sizeof(*mask), GFP_KERNEL);
 	if (!mask)
@@ -448,12 +451,11 @@ static int pcrypt_init_padata(struct padata_pcrypt *pcrypt,
 	free_cpumask_var(mask->mask);
 	kfree(mask);
 err_free_padata:
+	put_online_cpus();
 	padata_free(pcrypt->pinst);
 err_destroy_workqueue:
 	destroy_workqueue(pcrypt->wq);
 err:
-	put_online_cpus();
-
 	return ret;
 }
 
-- 
2.20.1