* [PATCH kernel] KVM: PPC: Book3S: Suppress failed alloc warning in H_COPY_TOFROM_GUEST
@ 2021-09-01 8:45 Alexey Kardashevskiy
2021-09-01 14:45 ` Fabiano Rosas
2021-12-15 0:40 ` Michael Ellerman
0 siblings, 2 replies; 3+ messages in thread
From: Alexey Kardashevskiy @ 2021-09-01 8:45 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Alexey Kardashevskiy, kvm-ppc
H_COPY_TOFROM_GUEST is an hcall for an upper level VM to access its nested
VMs memory. The userspace can trigger WARN_ON_ONCE(!(gfp & __GFP_NOWARN))
in __alloc_pages() by constructing a tiny VM which only does
H_COPY_TOFROM_GUEST with a too big GPR9 (number of bytes to copy).
This silences the warning by adding __GFP_NOWARN.
Spotted by syzkaller.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
arch/powerpc/kvm/book3s_hv_nested.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
index e57c08b968c0..a2e34efb8d31 100644
--- a/arch/powerpc/kvm/book3s_hv_nested.c
+++ b/arch/powerpc/kvm/book3s_hv_nested.c
@@ -580,7 +580,7 @@ long kvmhv_copy_tofrom_guest_nested(struct kvm_vcpu *vcpu)
if (eaddr & (0xFFFUL << 52))
return H_PARAMETER;
- buf = kzalloc(n, GFP_KERNEL);
+ buf = kzalloc(n, GFP_KERNEL | __GFP_NOWARN);
if (!buf)
return H_NO_MEM;
--
2.30.2
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH kernel] KVM: PPC: Book3S: Suppress failed alloc warning in H_COPY_TOFROM_GUEST
2021-09-01 8:45 [PATCH kernel] KVM: PPC: Book3S: Suppress failed alloc warning in H_COPY_TOFROM_GUEST Alexey Kardashevskiy
@ 2021-09-01 14:45 ` Fabiano Rosas
2021-12-15 0:40 ` Michael Ellerman
1 sibling, 0 replies; 3+ messages in thread
From: Fabiano Rosas @ 2021-09-01 14:45 UTC (permalink / raw)
To: Alexey Kardashevskiy, linuxppc-dev; +Cc: Alexey Kardashevskiy, kvm-ppc
Alexey Kardashevskiy <aik@ozlabs.ru> writes:
> H_COPY_TOFROM_GUEST is an hcall for an upper level VM to access its nested
> VMs memory. The userspace can trigger WARN_ON_ONCE(!(gfp & __GFP_NOWARN))
> in __alloc_pages() by constructing a tiny VM which only does
> H_COPY_TOFROM_GUEST with a too big GPR9 (number of bytes to copy).
>
> This silences the warning by adding __GFP_NOWARN.
>
> Spotted by syzkaller.
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
> arch/powerpc/kvm/book3s_hv_nested.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
> index e57c08b968c0..a2e34efb8d31 100644
> --- a/arch/powerpc/kvm/book3s_hv_nested.c
> +++ b/arch/powerpc/kvm/book3s_hv_nested.c
> @@ -580,7 +580,7 @@ long kvmhv_copy_tofrom_guest_nested(struct kvm_vcpu *vcpu)
> if (eaddr & (0xFFFUL << 52))
> return H_PARAMETER;
>
> - buf = kzalloc(n, GFP_KERNEL);
> + buf = kzalloc(n, GFP_KERNEL | __GFP_NOWARN);
> if (!buf)
> return H_NO_MEM;
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH kernel] KVM: PPC: Book3S: Suppress failed alloc warning in H_COPY_TOFROM_GUEST
2021-09-01 8:45 [PATCH kernel] KVM: PPC: Book3S: Suppress failed alloc warning in H_COPY_TOFROM_GUEST Alexey Kardashevskiy
2021-09-01 14:45 ` Fabiano Rosas
@ 2021-12-15 0:40 ` Michael Ellerman
1 sibling, 0 replies; 3+ messages in thread
From: Michael Ellerman @ 2021-12-15 0:40 UTC (permalink / raw)
To: Alexey Kardashevskiy, linuxppc-dev; +Cc: kvm-ppc
On Wed, 1 Sep 2021 18:45:50 +1000, Alexey Kardashevskiy wrote:
> H_COPY_TOFROM_GUEST is an hcall for an upper level VM to access its nested
> VMs memory. The userspace can trigger WARN_ON_ONCE(!(gfp & __GFP_NOWARN))
> in __alloc_pages() by constructing a tiny VM which only does
> H_COPY_TOFROM_GUEST with a too big GPR9 (number of bytes to copy).
>
> This silences the warning by adding __GFP_NOWARN.
>
> [...]
Applied to powerpc/next.
[1/1] KVM: PPC: Book3S: Suppress failed alloc warning in H_COPY_TOFROM_GUEST
https://git.kernel.org/powerpc/c/792020907b11c6f9246c21977cab3bad985ae4b6
cheers
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-09-01 8:45 [PATCH kernel] KVM: PPC: Book3S: Suppress failed alloc warning in H_COPY_TOFROM_GUEST Alexey Kardashevskiy
2021-09-01 14:45 ` Fabiano Rosas
2021-12-15 0:40 ` Michael Ellerman
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