[PATCH] KVM: PPC: Replace zero-length array with flexible array member

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 <redacted>
---
 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

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 <redacted>

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

Thanks
--
Gustavo

On Mon, Sep 20, 2021 at 07:05:07PM -0500, Gustavo A. R. Silva wrote:

On 9/18/21 09:21, Len Baker wrote:

quoted

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 <redacted>

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

I'm taking this in my -next tree.

Thanks
--
Gustavo