From: Alexey Kardashevskiy <aik@ozlabs.ru>
To: linuxppc-dev@lists.ozlabs.org
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>, kvm-ppc@vger.kernel.org
Subject: [PATCH kernel] KVM: PPC: Book3S: Suppress failed alloc warning in H_COPY_TOFROM_GUEST
Date: Wed, 1 Sep 2021 18:45:50 +1000 [thread overview]
Message-ID: <20210901084550.1658699-1-aik@ozlabs.ru> (raw)
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
next reply other threads:[~2021-09-01 8:46 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-01 8:45 Alexey Kardashevskiy [this message]
2021-09-01 14:45 ` [PATCH kernel] KVM: PPC: Book3S: Suppress failed alloc warning in H_COPY_TOFROM_GUEST Fabiano Rosas
2021-12-15 0:40 ` Michael Ellerman
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