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* [PATCH] KVM: PPC: Replace zero-length array with flexible array member
@ 2021-09-18 14:21 Len Baker
  2021-09-21  0:05 ` Gustavo A. R. Silva
  0 siblings, 1 reply; 3+ messages in thread
From: Len Baker @ 2021-09-18 14:21 UTC (permalink / raw)
  To: Paul Mackerras, Michael Ellerman, Benjamin Herrenschmidt
  Cc: Len Baker, Gustavo A. R. Silva, Kees Cook, kvm-ppc, linuxppc-dev,
	linux-hardening, linux-kernel

There is a regular need in the kernel to provide a way to declare having
a dynamically sized set of trailing elements in a structure. Kernel code
should always use "flexible array members" [1] for these cases. The
older style of one-element or zero-length arrays should no longer be
used[2].

Also, make use of the struct_size() helper in kzalloc().

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays

Signed-off-by: Len Baker <len.baker@gmx.com>
---
 arch/powerpc/include/asm/kvm_host.h | 2 +-
 arch/powerpc/kvm/book3s_64_vio.c    | 3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 080a7feb7731..3aed653373a5 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -190,7 +190,7 @@ struct kvmppc_spapr_tce_table {
 	u64 size;		/* window size in pages */
 	struct list_head iommu_tables;
 	struct mutex alloc_lock;
-	struct page *pages[0];
+	struct page *pages[];
 };

 /* XICS components, defined in book3s_xics.c */
diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
index 6365087f3160..d42b4b6d4a79 100644
--- a/arch/powerpc/kvm/book3s_64_vio.c
+++ b/arch/powerpc/kvm/book3s_64_vio.c
@@ -295,8 +295,7 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
 		return ret;

 	ret = -ENOMEM;
-	stt = kzalloc(sizeof(*stt) + npages * sizeof(struct page *),
-		      GFP_KERNEL);
+	stt = kzalloc(struct_size(stt, pages, npages), GFP_KERNEL);
 	if (!stt)
 		goto fail_acct;

--
2.25.1


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] KVM: PPC: Replace zero-length array with flexible array member
  2021-09-18 14:21 [PATCH] KVM: PPC: Replace zero-length array with flexible array member Len Baker
@ 2021-09-21  0:05 ` Gustavo A. R. Silva
  2021-10-20 23:28   ` Gustavo A. R. Silva
  0 siblings, 1 reply; 3+ messages in thread
From: Gustavo A. R. Silva @ 2021-09-21  0:05 UTC (permalink / raw)
  To: Len Baker, Paul Mackerras, Michael Ellerman, Benjamin Herrenschmidt
  Cc: Gustavo A. R. Silva, Kees Cook, kvm-ppc, linuxppc-dev,
	linux-hardening, linux-kernel



On 9/18/21 09:21, Len Baker wrote:
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use "flexible array members" [1] for these cases. The
> older style of one-element or zero-length arrays should no longer be
> used[2].
> 
> Also, make use of the struct_size() helper in kzalloc().
> 
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays
> 
> Signed-off-by: Len Baker <len.baker@gmx.com>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks
--
Gustavo

> ---
>  arch/powerpc/include/asm/kvm_host.h | 2 +-
>  arch/powerpc/kvm/book3s_64_vio.c    | 3 +--
>  2 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> index 080a7feb7731..3aed653373a5 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -190,7 +190,7 @@ struct kvmppc_spapr_tce_table {
>  	u64 size;		/* window size in pages */
>  	struct list_head iommu_tables;
>  	struct mutex alloc_lock;
> -	struct page *pages[0];
> +	struct page *pages[];
>  };
> 
>  /* XICS components, defined in book3s_xics.c */
> diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
> index 6365087f3160..d42b4b6d4a79 100644
> --- a/arch/powerpc/kvm/book3s_64_vio.c
> +++ b/arch/powerpc/kvm/book3s_64_vio.c
> @@ -295,8 +295,7 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
>  		return ret;
> 
>  	ret = -ENOMEM;
> -	stt = kzalloc(sizeof(*stt) + npages * sizeof(struct page *),
> -		      GFP_KERNEL);
> +	stt = kzalloc(struct_size(stt, pages, npages), GFP_KERNEL);
>  	if (!stt)
>  		goto fail_acct;
> 
> --
> 2.25.1
> 

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] KVM: PPC: Replace zero-length array with flexible array member
  2021-09-21  0:05 ` Gustavo A. R. Silva
@ 2021-10-20 23:28   ` Gustavo A. R. Silva
  0 siblings, 0 replies; 3+ messages in thread
From: Gustavo A. R. Silva @ 2021-10-20 23:28 UTC (permalink / raw)
  To: Gustavo A. R. Silva
  Cc: Len Baker, Paul Mackerras, Michael Ellerman,
	Benjamin Herrenschmidt, Kees Cook, kvm-ppc, linuxppc-dev,
	linux-hardening, linux-kernel

On Mon, Sep 20, 2021 at 07:05:07PM -0500, Gustavo A. R. Silva wrote:
> 
> 
> On 9/18/21 09:21, Len Baker wrote:
> > There is a regular need in the kernel to provide a way to declare having
> > a dynamically sized set of trailing elements in a structure. Kernel code
> > should always use "flexible array members" [1] for these cases. The
> > older style of one-element or zero-length arrays should no longer be
> > used[2].
> > 
> > Also, make use of the struct_size() helper in kzalloc().
> > 
> > [1] https://en.wikipedia.org/wiki/Flexible_array_member
> > [2] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays
> > 
> > Signed-off-by: Len Baker <len.baker@gmx.com>
> 
> Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

I'm taking this in my -next tree.

Thanks
--
Gustavo

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2021-10-20 23:24 UTC | newest]

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2021-09-18 14:21 [PATCH] KVM: PPC: Replace zero-length array with flexible array member Len Baker
2021-09-21  0:05 ` Gustavo A. R. Silva
2021-10-20 23:28   ` Gustavo A. R. Silva

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