From mboxrd@z Thu Jan 1 00:00:00 1970 From: Fabiano Rosas Date: Wed, 01 Sep 2021 14:45:09 +0000 Subject: Re: [PATCH kernel] KVM: PPC: Book3S: Suppress failed alloc warning in H_COPY_TOFROM_GUEST Message-Id: <87ilzkuzgq.fsf@linux.ibm.com> List-Id: References: <20210901084550.1658699-1-aik@ozlabs.ru> In-Reply-To: <20210901084550.1658699-1-aik@ozlabs.ru> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Alexey Kardashevskiy , linuxppc-dev@lists.ozlabs.org Cc: Alexey Kardashevskiy , kvm-ppc@vger.kernel.org Alexey Kardashevskiy 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 > --- Reviewed-by: Fabiano Rosas > 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;