2024-06-11 10:48:24

by Paolo Bonzini

Subject: [PATCH v2] virt: guest_memfd: fix reference leak on hwpoisoned page

If __kvm_gmem_get_pfn() detects an hwpoisoned page, it returns -EHWPOISON
but it does not put back the reference that kvm_gmem_get_folio() had
grabbed. Add the forgotten folio_put().

Fixes: a7800aa80ea4 ("KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory")
Cc: [email protected]
Signed-off-by: Paolo Bonzini <[email protected]>
---
Sent v1 from the wrong directory, sorry about that.

virt/kvm/guest_memfd.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 3bfe1824ec2d..19c220ec1efd 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -549,7 +549,6 @@ static int __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot,
struct kvm_gmem *gmem = file->private_data;
struct folio *folio;
struct page *page;
- int r;

if (file != slot->gmem.file) {
WARN_ON_ONCE(slot->gmem.file);
@@ -567,8 +566,9 @@ static int __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot,
return PTR_ERR(folio);

if (folio_test_hwpoison(folio)) {
- r = -EHWPOISON;
- goto out_unlock;
+ folio_unlock(folio);
+ folio_put(folio);
+ return -EHWPOISON;
}

page = folio_file_page(folio, index);
@@ -577,12 +577,8 @@ static int __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot,
if (max_order)
*max_order = 0;

- r = 0;
-
-out_unlock:
folio_unlock(folio);
-
- return r;
+ return 0;
}

int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
--
2.43.0

2024-06-12 12:22:47

by Liam Merwick

Subject: Re: [PATCH v2] virt: guest_memfd: fix reference leak on hwpoisoned page

On 11/06/2024 11:25, Paolo Bonzini wrote:
> If __kvm_gmem_get_pfn() detects an hwpoisoned page, it returns -EHWPOISON
> but it does not put back the reference that kvm_gmem_get_folio() had
> grabbed. Add the forgotten folio_put().
>
> Fixes: a7800aa80ea4 ("KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory")
> Cc: [email protected]
> Signed-off-by: Paolo Bonzini <[email protected]>


Reviewed-by: Liam Merwick <[email protected]>

2024-06-12 23:36:46

by Isaku Yamahata

Subject: Re: [PATCH v2] virt: guest_memfd: fix reference leak on hwpoisoned page

On Tue, Jun 11, 2024 at 06:25:15AM -0400,
Paolo Bonzini <[email protected]> wrote:

> If __kvm_gmem_get_pfn() detects an hwpoisoned page, it returns -EHWPOISON
> but it does not put back the reference that kvm_gmem_get_folio() had
> grabbed. Add the forgotten folio_put().
>
> Fixes: a7800aa80ea4 ("KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory")
> Cc: [email protected]
> Signed-off-by: Paolo Bonzini <[email protected]>

Reviewed-by: Isaku Yamahata <[email protected]>

--
Isaku Yamahata <[email protected]>