diff mbox series

KVM: x86: Reduce refcount if single_open() fails in kvm_mmu_rmaps_stat_open()

Message ID a75900413bb8b1e556be690e9588a0f92e946a30.1665733883.git.houwenlong.hwl@antgroup.com
State New
Headers
Series KVM: x86: Reduce refcount if single_open() fails in kvm_mmu_rmaps_stat_open() |

Commit Message

Hou Wenlong Oct. 14, 2022, 7:55 a.m. UTC 
  Refcount is increased before calling single_open() in
kvm_mmu_rmaps_stat_open(), If single_open() fails, refcount should be
restored, otherwise the vm couldn't be destroyed.

Fixes: 3bcd0662d66fd ("KVM: X86: Introduce mmu_rmaps_stat per-vm debugfs file")
Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
---
 arch/x86/kvm/debugfs.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Comments

Peter Xu Oct. 14, 2022, 2:09 p.m. UTC | #1 
On Fri, Oct 14, 2022 at 03:55:11PM +0800, Hou Wenlong wrote:
> Refcount is increased before calling single_open() in
> kvm_mmu_rmaps_stat_open(), If single_open() fails, refcount should be
> restored, otherwise the vm couldn't be destroyed.
> 
> Fixes: 3bcd0662d66fd ("KVM: X86: Introduce mmu_rmaps_stat per-vm debugfs file")
> Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
> ---
>  arch/x86/kvm/debugfs.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/debugfs.c b/arch/x86/kvm/debugfs.c
> index cfed36aba2f7..412ed1b341fa 100644
> --- a/arch/x86/kvm/debugfs.c
> +++ b/arch/x86/kvm/debugfs.c
> @@ -162,7 +162,12 @@ static int kvm_mmu_rmaps_stat_open(struct inode *inode, struct file *file)
>  	if (!kvm_get_kvm_safe(kvm))
>  		return -ENOENT;
>  
> -	return single_open(file, kvm_mmu_rmaps_stat_show, kvm);
> +	if (single_open(file, kvm_mmu_rmaps_stat_show, kvm)) {
> +		kvm_put_kvm(kvm);
> +		return -ENOMEM;
> +	}

Thanks for fixing this.  Would it be nicer to wire the single_open retval
(even though it'll only fail with -ENOMEM with current code base)?
Hou Wenlong Oct. 17, 2022, 2:54 a.m. UTC | #2 
On Fri, Oct 14, 2022 at 10:09:55PM +0800, Peter Xu wrote:
> On Fri, Oct 14, 2022 at 03:55:11PM +0800, Hou Wenlong wrote:
> > Refcount is increased before calling single_open() in
> > kvm_mmu_rmaps_stat_open(), If single_open() fails, refcount should be
> > restored, otherwise the vm couldn't be destroyed.
> > 
> > Fixes: 3bcd0662d66fd ("KVM: X86: Introduce mmu_rmaps_stat per-vm debugfs file")
> > Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
> > ---
> >  arch/x86/kvm/debugfs.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/kvm/debugfs.c b/arch/x86/kvm/debugfs.c
> > index cfed36aba2f7..412ed1b341fa 100644
> > --- a/arch/x86/kvm/debugfs.c
> > +++ b/arch/x86/kvm/debugfs.c
> > @@ -162,7 +162,12 @@ static int kvm_mmu_rmaps_stat_open(struct inode *inode, struct file *file)
> >  	if (!kvm_get_kvm_safe(kvm))
> >  		return -ENOENT;
> >  
> > -	return single_open(file, kvm_mmu_rmaps_stat_show, kvm);
> > +	if (single_open(file, kvm_mmu_rmaps_stat_show, kvm)) {
> > +		kvm_put_kvm(kvm);
> > +		return -ENOMEM;
> > +	}
> 
> Thanks for fixing this.  Would it be nicer to wire the single_open retval
> (even though it'll only fail with -ENOMEM with current code base)?
> 
I agree, it would be nicer to return the single_open() retval directly.
I just follow how failure of simple_attr_open() is handled in kvm_debugfs_open(),
but I think it should be changed too. 

> -- 
> Peter Xu
diff mbox series

Patch

diff --git a/arch/x86/kvm/debugfs.c b/arch/x86/kvm/debugfs.c
index cfed36aba2f7..412ed1b341fa 100644
--- a/arch/x86/kvm/debugfs.c
+++ b/arch/x86/kvm/debugfs.c
@@ -162,7 +162,12 @@  static int kvm_mmu_rmaps_stat_open(struct inode *inode, struct file *file)
 	if (!kvm_get_kvm_safe(kvm))
 		return -ENOENT;
 
-	return single_open(file, kvm_mmu_rmaps_stat_show, kvm);
+	if (single_open(file, kvm_mmu_rmaps_stat_show, kvm)) {
+		kvm_put_kvm(kvm);
+		return -ENOMEM;
+	}
+
+	return 0;
 }
 
 static int kvm_mmu_rmaps_stat_release(struct inode *inode, struct file *file)