On Tue, Mar 3, 2026 at 7:42 AM Ricardo Robaina <[email protected]> wrote:
>
> Currently, audit_receive_msg() ignores unknown status bits in AUDIT_SET
> requests, incorrectly returning success to newer user space tools
> querying unsupported features. This breaks forward compatibility.
>
> Fix this by defining AUDIT_STATUS_ALL in the UAPI header and returning
> -EINVAL if any unrecognized bits are set (s.mask & ~AUDIT_STATUS_ALL).
> This ensures invalid requests are safely rejected, allowing user space
> to reliably test for and gracefully handle feature detection on older
> kernels.
>
> Suggested-by: Steve Grubb <[email protected]>
> Signed-off-by: Ricardo Robaina <[email protected]>
> ---
> include/uapi/linux/audit.h | 9 +++++++++
> kernel/audit.c | 2 ++
> 2 files changed, 11 insertions(+)
>
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index 14a1c1fe013a..1d5122b9274a 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -356,6 +356,15 @@ enum {
> #define AUDIT_STATUS_LOST 0x0040
> #define AUDIT_STATUS_BACKLOG_WAIT_TIME_ACTUAL 0x0080
>
> +#define AUDIT_STATUS_ALL (AUDIT_STATUS_ENABLED | \
> + AUDIT_STATUS_FAILURE | \
> + AUDIT_STATUS_PID | \
> + AUDIT_STATUS_RATE_LIMIT | \
> + AUDIT_STATUS_BACKLOG_LIMIT | \
> + AUDIT_STATUS_BACKLOG_WAIT_TIME | \
> + AUDIT_STATUS_LOST | \
> + AUDIT_STATUS_BACKLOG_WAIT_TIME_ACTUAL)
Overall I think this is fine and good, but AUDIT_STATUS_ALL doesn't
need to be in the UAPI so why don't we move it to
include/linux/audit.h? You can put it at the very top, right above
the AUDIT_INO_UNSET macro.
> #define AUDIT_FEATURE_BITMAP_BACKLOG_LIMIT 0x00000001
> #define AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_TIME 0x00000002
> #define AUDIT_FEATURE_BITMAP_EXECUTABLE_PATH 0x00000004
> diff --git a/kernel/audit.c b/kernel/audit.c
> index 5a0216056524..592383dce090 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -1295,6 +1295,8 @@ static int audit_receive_msg(struct sk_buff *skb,
> struct nlmsghdr *nlh,
> memset(&s, 0, sizeof(s));
> /* guard against past and future API changes */
> memcpy(&s, data, min_t(size_t, sizeof(s), data_len));
> + if (s.mask & ~AUDIT_STATUS_ALL)
> + return -EINVAL;
> if (s.mask & AUDIT_STATUS_ENABLED) {
> err = audit_set_enabled(s.enabled);
> if (err < 0)
> --
> 2.53.0
--
paul-moore.com
