2022-10-17 03:09:37

by Hou Wenlong

Subject: [PATCH v2 1/2] KVM: x86: Reduce refcount if single_open() fails in kvm_mmu_rmaps_stat_open()

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 <[email protected]>
---
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..e6efd0821c59 100644
--- a/arch/x86/kvm/debugfs.c
+++ b/arch/x86/kvm/debugfs.c
@@ -157,12 +157,17 @@ static int kvm_mmu_rmaps_stat_show(struct seq_file *m, void *v)

static int kvm_mmu_rmaps_stat_open(struct inode *inode, struct file *file)
{
+ int ret;
struct kvm *kvm = inode->i_private;

if (!kvm_get_kvm_safe(kvm))
return -ENOENT;

- return single_open(file, kvm_mmu_rmaps_stat_show, kvm);
+ ret = single_open(file, kvm_mmu_rmaps_stat_show, kvm);
+ if (ret)
+ kvm_put_kvm(kvm);
+
+ return ret;
}

static int kvm_mmu_rmaps_stat_release(struct inode *inode, struct file *file)
--
2.31.1

2022-10-17 03:23:22

by Hou Wenlong

Subject: [PATCH v2 2/2] KVM: debugfs: Return retval of simple_attr_open() if it fails

Although simple_attr_open() fails only with -ENOMEM with current code
base, it would be nicer to return retval of simple_attr_open() directly
in kvm_debugfs_open().

No functional change intended.

Signed-off-by: Hou Wenlong <[email protected]>
---
virt/kvm/kvm_main.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e30f1b4ecfa5..f7b06c1e8827 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -5398,6 +5398,7 @@ static int kvm_debugfs_open(struct inode *inode, struct file *file,
int (*get)(void *, u64 *), int (*set)(void *, u64),
const char *fmt)
{
+ int ret;
struct kvm_stat_data *stat_data = (struct kvm_stat_data *)
inode->i_private;

@@ -5409,15 +5410,13 @@ static int kvm_debugfs_open(struct inode *inode, struct file *file,
if (!kvm_get_kvm_safe(stat_data->kvm))
return -ENOENT;

- if (simple_attr_open(inode, file, get,
- kvm_stats_debugfs_mode(stat_data->desc) & 0222
- ? set : NULL,
- fmt)) {
+ ret = simple_attr_open(inode, file, get,
+ kvm_stats_debugfs_mode(stat_data->desc) & 0222
+ ? set : NULL, fmt);
+ if (ret)
kvm_put_kvm(stat_data->kvm);
- return -ENOMEM;
- }

- return 0;
+ return ret;
}

static int kvm_debugfs_release(struct inode *inode, struct file *file)
--
2.31.1

2022-10-17 18:11:46

by Peter Xu

Subject: Re: [PATCH v2 1/2] KVM: x86: Reduce refcount if single_open() fails in kvm_mmu_rmaps_stat_open()

On Mon, Oct 17, 2022 at 11:06:09AM +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 <[email protected]>

Reviewed-by: Peter Xu <[email protected]>

Thanks,

--
Peter Xu

2022-10-22 11:28:48

by Paolo Bonzini

Subject: Re: [PATCH v2 2/2] KVM: debugfs: Return retval of simple_attr_open() if it fails

On 10/17/22 05:06, Hou Wenlong wrote:
> Although simple_attr_open() fails only with -ENOMEM with current code
> base, it would be nicer to return retval of simple_attr_open() directly
> in kvm_debugfs_open().
>
> No functional change intended.
>
> Signed-off-by: Hou Wenlong <[email protected]>
> ---
> virt/kvm/kvm_main.c | 13 ++++++-------
> 1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index e30f1b4ecfa5..f7b06c1e8827 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -5398,6 +5398,7 @@ static int kvm_debugfs_open(struct inode *inode, struct file *file,
> int (*get)(void *, u64 *), int (*set)(void *, u64),
> const char *fmt)
> {
> + int ret;
> struct kvm_stat_data *stat_data = (struct kvm_stat_data *)
> inode->i_private;
>
> @@ -5409,15 +5410,13 @@ static int kvm_debugfs_open(struct inode *inode, struct file *file,
> if (!kvm_get_kvm_safe(stat_data->kvm))
> return -ENOENT;
>
> - if (simple_attr_open(inode, file, get,
> - kvm_stats_debugfs_mode(stat_data->desc) & 0222
> - ? set : NULL,
> - fmt)) {
> + ret = simple_attr_open(inode, file, get,
> + kvm_stats_debugfs_mode(stat_data->desc) & 0222
> + ? set : NULL, fmt);
> + if (ret)
> kvm_put_kvm(stat_data->kvm);
> - return -ENOMEM;
> - }
>
> - return 0;
> + return ret;
> }
>
> static int kvm_debugfs_release(struct inode *inode, struct file *file)

Queued, thanks.

Paolo