Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).
While there, use struct_size() helper, instead of the open-coded
version, to calculate the size for the allocation of the whole
flexible structure, including of course, the flexible-array member.
This code was found with the help of Coccinelle, and audited and
fixed manually.
Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
drivers/iommu/virtio-iommu.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
index 17dcd826f5c2..379ebe03efb6 100644
--- a/drivers/iommu/virtio-iommu.c
+++ b/drivers/iommu/virtio-iommu.c
@@ -85,7 +85,7 @@ struct viommu_request {
void *writeback;
unsigned int write_offset;
unsigned int len;
- char buf[];
+ char buf[] __counted_by(len);
};
#define VIOMMU_FAULT_RESV_MASK 0xffffff00
@@ -230,7 +230,7 @@ static int __viommu_add_req(struct viommu_dev *viommu, void *buf, size_t len,
if (write_offset <= 0)
return -EINVAL;
- req = kzalloc(sizeof(*req) + len, GFP_ATOMIC);
+ req = kzalloc(struct_size(req, buf, len), GFP_ATOMIC);
if (!req)
return -ENOMEM;
--
2.34.1
On Mon, Oct 9, 2023 at 11:24 AM Gustavo A. R. Silva
<[email protected]> wrote:
>
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
> array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
>
> While there, use struct_size() helper, instead of the open-coded
> version, to calculate the size for the allocation of the whole
> flexible structure, including of course, the flexible-array member.
>
> This code was found with the help of Coccinelle, and audited and
> fixed manually.
>
> Signed-off-by: Gustavo A. R. Silva <[email protected]>
> ---
> drivers/iommu/virtio-iommu.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
> index 17dcd826f5c2..379ebe03efb6 100644
> --- a/drivers/iommu/virtio-iommu.c
> +++ b/drivers/iommu/virtio-iommu.c
> @@ -85,7 +85,7 @@ struct viommu_request {
> void *writeback;
> unsigned int write_offset;
> unsigned int len;
> - char buf[];
> + char buf[] __counted_by(len);
> };
>
> #define VIOMMU_FAULT_RESV_MASK 0xffffff00
> @@ -230,7 +230,7 @@ static int __viommu_add_req(struct viommu_dev *viommu, void *buf, size_t len,
> if (write_offset <= 0)
> return -EINVAL;
>
> - req = kzalloc(sizeof(*req) + len, GFP_ATOMIC);
> + req = kzalloc(struct_size(req, buf, len), GFP_ATOMIC);
> if (!req)
> return -ENOMEM;
>
> --
> 2.34.1
>
>
The __counted_by annotation and the usage of struct_size look right!
Reviewed-by: Justin Stitt <[email protected]>
On Mon, Oct 09, 2023 at 12:24:27PM -0600, Gustavo A. R. Silva wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
> array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
>
> While there, use struct_size() helper, instead of the open-coded
> version, to calculate the size for the allocation of the whole
> flexible structure, including of course, the flexible-array member.
>
> This code was found with the help of Coccinelle, and audited and
> fixed manually.
>
> Signed-off-by: Gustavo A. R. Silva <[email protected]>
Reviewed-by: Jean-Philippe Brucker <[email protected]>
> ---
> drivers/iommu/virtio-iommu.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
> index 17dcd826f5c2..379ebe03efb6 100644
> --- a/drivers/iommu/virtio-iommu.c
> +++ b/drivers/iommu/virtio-iommu.c
> @@ -85,7 +85,7 @@ struct viommu_request {
> void *writeback;
> unsigned int write_offset;
> unsigned int len;
> - char buf[];
> + char buf[] __counted_by(len);
> };
>
> #define VIOMMU_FAULT_RESV_MASK 0xffffff00
> @@ -230,7 +230,7 @@ static int __viommu_add_req(struct viommu_dev *viommu, void *buf, size_t len,
> if (write_offset <= 0)
> return -EINVAL;
>
> - req = kzalloc(sizeof(*req) + len, GFP_ATOMIC);
> + req = kzalloc(struct_size(req, buf, len), GFP_ATOMIC);
> if (!req)
> return -ENOMEM;
>
> --
> 2.34.1
>
On Mon, Oct 09, 2023 at 12:24:27PM -0600, Gustavo A. R. Silva wrote:
> drivers/iommu/virtio-iommu.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
Applied, thanks.