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KVM: PPC: Book3S: Suppress failed alloc warning in H_COPY_TOFROM_GUEST

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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>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210901084550.1658699-1-aik@ozlabs.ru
This commit is contained in:
Alexey Kardashevskiy 2021-09-01 18:45:50 +10:00 committed by Michael Ellerman
parent 511d25d6b7
commit 792020907b
1 changed files with 1 additions and 1 deletions
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2
arch/powerpc/kvm/book3s_hv_nested.c
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@ -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;