linux-kernel - [PATCH] KVM: explain missing kvm_put

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Date:   Tue, 27 Jun 2017 15:46:57 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     imbrenda@...ux.vnet.ibm.com, Al Viro <viro@...IV.linux.org.uk>,
        borntraeger@...ibm.com, frankja@...ux.vnet.ibm.com
Subject: [PATCH] KVM: explain missing kvm_put_kvm in case of failure

The call to kvm_put_kvm was removed from error handling in commit
506cfba9e726 ("KVM: don't use anon_inode_getfd() before possible
failures"), but it is _not_ a memory leak.  Reuse Al's explanation
to avoid that someone else makes the same mistake.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 virt/kvm/kvm_main.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 3863cf7ae1a3..19f0ecb9b93e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3191,6 +3191,12 @@ static int kvm_dev_ioctl_create_vm(unsigned long type)
 		return PTR_ERR(file);
 	}
 
+	/*
+	 * Don't call kvm_put_kvm anymore at this point; file->f_op is
+	 * already set, with ->release() being kvm_vm_release().  In error
+	 * cases it will be called by the final fput(file) and will take
+	 * care of doing kvm_put_kvm(kvm).
+	 */
 	if (kvm_create_vm_debugfs(kvm, r) < 0) {
 		put_unused_fd(r);
 		fput(file);
-- 
1.8.3.1