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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


WARNING: multiple messages have this Message-ID (diff)
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, 01 Sep 2021 08:45:50 +0000	[thread overview]
Message-ID: <20210901084550.1658699-1-aik@ozlabs.ru> (raw)
In-Reply-To: <20210901084512.1658628-1-aik@ozlabs.ru>

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

             reply	other threads:[~2021-09-01  8:46 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-01  8:45 Alexey Kardashevskiy [this message]
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
2021-09-01 14:45   ` Fabiano Rosas
2021-12-15  0:40 ` Michael Ellerman
2021-12-15  0:40   ` Michael Ellerman
  -- strict thread matches above, loose matches on Subject: below --
2021-09-01  8:45 [PATCH kernel] KVM: PPC: Book3S: Suppress warnings when allocating too big memory slots Alexey Kardashevskiy
2021-09-01  8:45 ` Alexey Kardashevskiy
2021-09-01 14:59 ` Fabiano Rosas
2021-09-01 14:59   ` Fabiano Rosas
2021-09-02  4:25   ` Alexey Kardashevskiy
2021-09-02  4:25     ` Alexey Kardashevskiy
2021-09-02 13:08     ` Fabiano Rosas
2021-09-02 13:08       ` Fabiano Rosas
2021-09-02 13:23       ` David Laight
2021-09-02 13:23         ` David Laight
2021-12-15  0:40 ` Michael Ellerman
2021-12-15  0:40   ` Michael Ellerman

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