On Wednesday, September 24, 2014 10:07:20 AM Richard Guy Briggs wrote:
> A regression was caused by commit 780a7654cee8:
> audit: Make testing for a valid loginuid explicit.
> (which in turn attempted to fix a regression caused by e1760bd)
>
> When audit_krule_to_data() fills in the rules to get a listing, there was a
> missing clause to convert back from AUDIT_LOGINUID_SET to AUDIT_LOGINUID.
>
> This broke userspace by not returning the same information that was sent and
> expected.
>
> The rule:
> auditctl -a exit,never -F auid=-1
> gives:
> auditctl -l
> LIST_RULES: exit,never f24=0 syscall=all
> when it should give:
> LIST_RULES: exit,never auid=-1 (0xffffffff) syscall=all
>
> Tag it so that it is reported the same way it was set.
>
> Note: move the field validation call ahead of the mutation code to have it
> work on the original field set.
>
> Signed-off-by: Richard Guy Briggs <[email protected]>
> ---
> include/uapi/linux/audit.h | 3 +++
> kernel/auditfilter.c | 19 +++++++++++++------
> kernel/auditsc.c | 2 +-
> 3 files changed, 17 insertions(+), 7 deletions(-)
Sorry for the delays, I'm working on cleaning out the audit bug/patch backlog
and it took me a little while to get to this topic ... so, this looks a messy
little problem; Richard, could you help me understand things a bit better?
As I understand it, when old userspace would set a filter with AUDIT_LOGINUID
but when it listed the audit rules in the kernel it would see
AUDIT_LOGINUID_SET, yes? This patch attempts to fix this by marking a legacy
userspace with the AUDIT_LOGINUID_LEGACY bitmask on the internal kernel
representation so that when the rules are dumped to userspace the
AUDIT_LOGINUID_SET rule can be rewritten as AUDIT_LOGINUID, yes?
However, there are some things that are not immediately obvious to me:
* Why are we using a bit in audit_field->type to indicate the legacy nature of
userspace?
* Why are we reusing the AUDIT_NEGATE bit in the type field to indicate a
legacy userspace?
* Why are we not using something in audit_krule? Without looking to in depth
it would appear that there are multiple fields which might be useful, e.g.
"vers_ops", "flags"?
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index 4d100c8..860df86 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -274,6 +274,9 @@
>
> #define AUDIT_FILTERKEY 210
>
> +/* Flag to indicate legacy AUDIT_LOGINUID unset usage */
> +#define AUDIT_LOGINUID_LEGACY 0x80000000
> +
> #define AUDIT_NEGATE 0x80000000
>
> /* These are the supported operators.
> diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
> index 40ed981..39ce3e6 100644
> --- a/kernel/auditfilter.c
> +++ b/kernel/auditfilter.c
> @@ -438,9 +438,13 @@ static struct audit_entry *audit_data_to_entry(struct
> audit_rule_data *data, f->type = data->fields[i];
> f->val = data->values[i];
>
> + err = audit_field_valid(entry, f);
> + if (err)
> + goto exit_free;
> +
> /* Support legacy tests for a valid loginuid */
> if ((f->type == AUDIT_LOGINUID) && (f->val == AUDIT_UID_UNSET))
> {
> - f->type = AUDIT_LOGINUID_SET;
> + f->type = AUDIT_LOGINUID_SET | AUDIT_LOGINUID_LEGACY;
> f->val = 0;
> }
>
> @@ -457,10 +461,6 @@ static struct audit_entry *audit_data_to_entry(struct
> audit_rule_data *data, rcu_read_unlock();
> }
>
> - err = audit_field_valid(entry, f);
> - if (err)
> - goto exit_free;
> -
> err = -EINVAL;
> switch (f->type) {
> case AUDIT_LOGINUID:
> @@ -630,6 +630,13 @@ static struct audit_rule_data
> *audit_krule_to_data(struct audit_krule *krule) data->buflen +=
> data->values[i] =
> audit_pack_string(&bufp, krule->filterkey);
> break;
> + case AUDIT_LOGINUID_SET | AUDIT_LOGINUID_LEGACY:
> + if (!f->val) {
> + data->fields[i] = AUDIT_LOGINUID;
> + data->values[i] = AUDIT_UID_UNSET;
> + break;
> + }
> + /* fallthrough if set */
> default:
> data->values[i] = f->val;
> }
> @@ -1270,7 +1277,7 @@ static int audit_filter_user_rules(struct audit_krule
> *rule, int type, int result = 0;
> u32 sid;
>
> - switch (f->type) {
> + switch (f->type & ~AUDIT_LOGINUID_LEGACY) {
> case AUDIT_PID:
> pid = task_pid_nr(current);
> result = audit_comparator(pid, f->op, f->val);
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 8933572..ef25cbc 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -452,7 +452,7 @@ static int audit_filter_rules(struct task_struct *tsk,
> int result = 0;
> pid_t pid;
>
> - switch (f->type) {
> + switch (f->type & ~AUDIT_LOGINUID_LEGACY) {
> case AUDIT_PID:
> pid = task_pid_nr(tsk);
> result = audit_comparator(pid, f->op, f->val);
--
paul moore
security and virtualization @ redhat
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