linux-kernel - [PATCH] kvm/vfio: Fix potential deadlock problem in vfio

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Message-Id: <20220517023441.4258-1-wanjiabing@vivo.com>
Date:   Tue, 17 May 2022 10:34:41 +0800
From:   Wan Jiabing <wanjiabing@...o.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Yi Liu <yi.l.liu@...el.com>, Kevin Tian <kevin.tian@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Wan Jiabing <wanjiabing@...o.com>
Subject: [PATCH] kvm/vfio: Fix potential deadlock problem in vfio

Fix following coccicheck warning:
./virt/kvm/vfio.c:258:1-7: preceding lock on line 236

If kvm_vfio_file_iommu_group() failed, code would goto err_fdput with
mutex_lock acquired and then return ret. It might cause potential
deadlock. Move mutex_unlock bellow err_fdput tag to fix it. 

Fixes: d55d9e7a45721 ("kvm/vfio: Store the struct file in the kvm_vfio_group")
Signed-off-by: Wan Jiabing <wanjiabing@...o.com>
---
 virt/kvm/vfio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
index 8f9f7fffb96a..ce1b01d02c51 100644
--- a/virt/kvm/vfio.c
+++ b/virt/kvm/vfio.c
@@ -252,8 +252,8 @@ static int kvm_vfio_group_set_spapr_tce(struct kvm_device *dev,
 		break;
 	}
 
-	mutex_unlock(&kv->lock);
 err_fdput:
+	mutex_unlock(&kv->lock);
 	fdput(f);
 	return ret;
 }
-- 
2.36.1