* [PATCH net-next 2/2] KEYS: annotate struct user_key_payload with __counted_by
[not found] <20260406175810.1018681-3-thorsten.blum@linux.dev>
@ 2026-04-06 17:58 ` Thorsten Blum
2026-04-08 9:02 ` Jarkko Sakkinen
0 siblings, 1 reply; 3+ messages in thread
From: Thorsten Blum @ 2026-04-06 17:58 UTC (permalink / raw)
To: David Howells, Jarkko Sakkinen, Kees Cook, Gustavo A. R. Silva
Cc: Thorsten Blum, keyrings, linux-kernel, linux-hardening
Add the __counted_by() compiler attribute to the flexible array member
'data' to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
CONFIG_FORTIFY_SOURCE.
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
include/keys/user-type.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/include/keys/user-type.h b/include/keys/user-type.h
index 386c31432789..2305991f4fcd 100644
--- a/include/keys/user-type.h
+++ b/include/keys/user-type.h
@@ -27,7 +27,8 @@
struct user_key_payload {
struct rcu_head rcu; /* RCU destructor */
unsigned short datalen; /* length of this data */
- char data[] __aligned(__alignof__(u64)); /* actual data */
+ char data[] /* actual data */
+ __aligned(__alignof__(u64)) __counted_by(datalen);
};
extern struct key_type key_type_user;
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH net-next 2/2] KEYS: annotate struct user_key_payload with __counted_by
2026-04-06 17:58 ` [PATCH net-next 2/2] KEYS: annotate struct user_key_payload with __counted_by Thorsten Blum
@ 2026-04-08 9:02 ` Jarkko Sakkinen
2026-04-08 12:21 ` Thorsten Blum
0 siblings, 1 reply; 3+ messages in thread
From: Jarkko Sakkinen @ 2026-04-08 9:02 UTC (permalink / raw)
To: Thorsten Blum
Cc: David Howells, Kees Cook, Gustavo A. R. Silva, keyrings,
linux-kernel, linux-hardening
On Mon, Apr 06, 2026 at 07:58:10PM +0200, Thorsten Blum wrote:
> Add the __counted_by() compiler attribute to the flexible array member
> 'data' to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
> CONFIG_FORTIFY_SOURCE.
>
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> ---
> include/keys/user-type.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/keys/user-type.h b/include/keys/user-type.h
> index 386c31432789..2305991f4fcd 100644
> --- a/include/keys/user-type.h
> +++ b/include/keys/user-type.h
> @@ -27,7 +27,8 @@
> struct user_key_payload {
> struct rcu_head rcu; /* RCU destructor */
> unsigned short datalen; /* length of this data */
> - char data[] __aligned(__alignof__(u64)); /* actual data */
> + char data[] /* actual data */
> + __aligned(__alignof__(u64)) __counted_by(datalen);
> };
>
> extern struct key_type key_type_user;
You don't provide any evidence of any improvement.
BR, Jarkko
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH net-next 2/2] KEYS: annotate struct user_key_payload with __counted_by
2026-04-08 9:02 ` Jarkko Sakkinen
@ 2026-04-08 12:21 ` Thorsten Blum
0 siblings, 0 replies; 3+ messages in thread
From: Thorsten Blum @ 2026-04-08 12:21 UTC (permalink / raw)
To: Jarkko Sakkinen
Cc: David Howells, Kees Cook, Gustavo A. R. Silva, keyrings,
linux-kernel, linux-hardening
On Wed, Apr 08, 2026 at 12:02:25PM +0300, Jarkko Sakkinen wrote:
> On Mon, Apr 06, 2026 at 07:58:10PM +0200, Thorsten Blum wrote:
> > Add the __counted_by() compiler attribute to the flexible array member
> > 'data' to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
> > CONFIG_FORTIFY_SOURCE.
> >
> > Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> > ---
> > include/keys/user-type.h | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/keys/user-type.h b/include/keys/user-type.h
> > index 386c31432789..2305991f4fcd 100644
> > --- a/include/keys/user-type.h
> > +++ b/include/keys/user-type.h
> > @@ -27,7 +27,8 @@
> > struct user_key_payload {
> > struct rcu_head rcu; /* RCU destructor */
> > unsigned short datalen; /* length of this data */
> > - char data[] __aligned(__alignof__(u64)); /* actual data */
> > + char data[] /* actual data */
> > + __aligned(__alignof__(u64)) __counted_by(datalen);
> > };
> >
> > extern struct key_type key_type_user;
>
> You don't provide any evidence of any improvement.
It's a proactive hardening change to help avoid future mistakes.
The __counted_by() annotation makes the bounds visible to the compiler
and at runtime so that future ->data accesses can be checked against
->datalen.
The current code is correct regarding ->data accesses and doesn't
require any changes.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2026-04-06 17:58 ` [PATCH net-next 2/2] KEYS: annotate struct user_key_payload with __counted_by Thorsten Blum
2026-04-08 9:02 ` Jarkko Sakkinen
2026-04-08 12:21 ` Thorsten Blum
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