2023-10-03 23:19:02

by Kees Cook

Subject: [PATCH] xfrm: Annotate struct xfrm_sec_ctx with __counted_by

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).

As found with Coccinelle[1], add __counted_by for struct xfrm_sec_ctx.

Cc: Steffen Klassert <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: [email protected]
Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
Signed-off-by: Kees Cook <[email protected]>
---
include/uapi/linux/xfrm.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h
index 23543c33fee8..6a77328be114 100644
--- a/include/uapi/linux/xfrm.h
+++ b/include/uapi/linux/xfrm.h
@@ -4,6 +4,7 @@

#include <linux/in6.h>
#include <linux/types.h>
+#include <linux/stddef.h>

/* All of the structures in this file may not change size as they are
* passed into the kernel from userspace via netlink sockets.
@@ -33,7 +34,7 @@ struct xfrm_sec_ctx {
__u8 ctx_alg;
__u16 ctx_len;
__u32 ctx_sid;
- char ctx_str[];
+ char ctx_str[] __counted_by(ctx_len);
};

/* Security Context Domains of Interpretation */
--
2.34.1

2023-10-04 01:52:03

by Gustavo A. R. Silva

Subject: Re: [PATCH] xfrm: Annotate struct xfrm_sec_ctx with __counted_by

On 10/4/23 01:18, Kees Cook 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).
>
> As found with Coccinelle[1], add __counted_by for struct xfrm_sec_ctx.
>
> Cc: Steffen Klassert <[email protected]>
> Cc: Herbert Xu <[email protected]>
> Cc: "David S. Miller" <[email protected]>
> Cc: [email protected]
> Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
> Signed-off-by: Kees Cook <[email protected]>

Reviewed-by: Gustavo A. R. Silva <[email protected]>

Thanks
--
Gustavo

> ---
> include/uapi/linux/xfrm.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h
> index 23543c33fee8..6a77328be114 100644
> --- a/include/uapi/linux/xfrm.h
> +++ b/include/uapi/linux/xfrm.h
> @@ -4,6 +4,7 @@
>
> #include <linux/in6.h>
> #include <linux/types.h>
> +#include <linux/stddef.h>
>
> /* All of the structures in this file may not change size as they are
> * passed into the kernel from userspace via netlink sockets.
> @@ -33,7 +34,7 @@ struct xfrm_sec_ctx {
> __u8 ctx_alg;
> __u16 ctx_len;
> __u32 ctx_sid;
> - char ctx_str[];
> + char ctx_str[] __counted_by(ctx_len);
> };
>
> /* Security Context Domains of Interpretation */

2023-10-06 05:47:52

by Steffen Klassert

Subject: Re: [PATCH] xfrm: Annotate struct xfrm_sec_ctx with __counted_by

On Tue, Oct 03, 2023 at 04:18:28PM -0700, Kees Cook 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).
>
> As found with Coccinelle[1], add __counted_by for struct xfrm_sec_ctx.
>
> Cc: Steffen Klassert <[email protected]>
> Cc: Herbert Xu <[email protected]>
> Cc: "David S. Miller" <[email protected]>
> Cc: [email protected]
> Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
> Signed-off-by: Kees Cook <[email protected]>

Applied to ipsec-next, thanks!