Replace the single skb pointer in an audit_buffer with
a list of skb pointers. Add the audit_stamp information
to the audit_buffer as there's no guarantee that there
will be an audit_context containing the stamp associated
with the event. At audit_log_end() time create auxiliary
records (none are currently defined) as have been added
to the list.
Suggested-by: Paul Moore <[email protected]>
Signed-off-by: Casey Schaufler <[email protected]>
---
kernel/audit.c | 62 +++++++++++++++++++++++++++++++-------------------
1 file changed, 39 insertions(+), 23 deletions(-)
diff --git a/kernel/audit.c b/kernel/audit.c
index 6b6c089512f7..4d44c05053b0 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -197,8 +197,10 @@ static struct audit_ctl_mutex {
* to place it on a transmit queue. Multiple audit_buffers can be in
* use simultaneously. */
struct audit_buffer {
- struct sk_buff *skb; /* formatted skb ready to send */
+ struct sk_buff *skb; /* the skb for audit_log functions */
+ struct sk_buff_head skb_list; /* formatted skbs, ready to send */
struct audit_context *ctx; /* NULL or associated context */
+ struct audit_stamp stamp; /* audit stamp for these records */
gfp_t gfp_mask;
};
@@ -1765,10 +1767,13 @@ __setup("audit_backlog_limit=", audit_backlog_limit_set);
static void audit_buffer_free(struct audit_buffer *ab)
{
+ struct sk_buff *skb;
+
if (!ab)
return;
- kfree_skb(ab->skb);
+ while((skb = skb_dequeue(&ab->skb_list)))
+ kfree_skb(skb);
kmem_cache_free(audit_buffer_cache, ab);
}
@@ -1784,8 +1789,12 @@ static struct audit_buffer *audit_buffer_alloc(struct audit_context *ctx,
ab->skb = nlmsg_new(AUDIT_BUFSIZ, gfp_mask);
if (!ab->skb)
goto err;
+
+ skb_queue_head_init(&ab->skb_list);
+ skb_queue_tail(&ab->skb_list, ab->skb);
+
if (!nlmsg_put(ab->skb, 0, 0, type, 0, 0))
- goto err;
+ kfree_skb(ab->skb);
ab->ctx = ctx;
ab->gfp_mask = gfp_mask;
@@ -1849,7 +1858,6 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
int type)
{
struct audit_buffer *ab;
- struct audit_stamp stamp;
if (audit_initialized != AUDIT_INITIALIZED)
return NULL;
@@ -1904,14 +1912,14 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
return NULL;
}
- audit_get_stamp(ab->ctx, &stamp);
+ audit_get_stamp(ab->ctx, &ab->stamp);
/* cancel dummy context to enable supporting records */
if (ctx)
ctx->dummy = 0;
audit_log_format(ab, "audit(%llu.%03lu:%u): ",
- (unsigned long long)stamp.ctime.tv_sec,
- stamp.ctime.tv_nsec/1000000,
- stamp.serial);
+ (unsigned long long)ab->stamp.ctime.tv_sec,
+ ab->stamp.ctime.tv_nsec/1000000,
+ ab->stamp.serial);
return ab;
}
@@ -2402,26 +2410,14 @@ int audit_signal_info(int sig, struct task_struct *t)
}
/**
- * audit_log_end - end one audit record
- * @ab: the audit_buffer
- *
- * We can not do a netlink send inside an irq context because it blocks (last
- * arg, flags, is not set to MSG_DONTWAIT), so the audit buffer is placed on a
- * queue and a kthread is scheduled to remove them from the queue outside the
- * irq context. May be called in any context.
+ * __audit_log_end - enqueue one audit record
+ * @skb: the buffer to send
*/
-void audit_log_end(struct audit_buffer *ab)
+static void __audit_log_end(struct sk_buff *skb)
{
- struct sk_buff *skb;
struct nlmsghdr *nlh;
- if (!ab)
- return;
-
if (audit_rate_check()) {
- skb = ab->skb;
- ab->skb = NULL;
-
/* setup the netlink header, see the comments in
* kauditd_send_multicast_skb() for length quirks */
nlh = nlmsg_hdr(skb);
@@ -2432,6 +2428,26 @@ void audit_log_end(struct audit_buffer *ab)
wake_up_interruptible(&kauditd_wait);
} else
audit_log_lost("rate limit exceeded");
+}
+
+/**
+ * audit_log_end - end one audit record
+ * @ab: the audit_buffer
+ *
+ * We can not do a netlink send inside an irq context because it blocks (last
+ * arg, flags, is not set to MSG_DONTWAIT), so the audit buffer is placed on a
+ * queue and a kthread is scheduled to remove them from the queue outside the
+ * irq context. May be called in any context.
+ */
+void audit_log_end(struct audit_buffer *ab)
+{
+ struct sk_buff *skb;
+
+ if (!ab)
+ return;
+
+ while ((skb = skb_dequeue(&ab->skb_list)))
+ __audit_log_end(skb);
audit_buffer_free(ab);
}
--
2.35.1
On Mon, Apr 18, 2022 at 11:12 AM Casey Schaufler <[email protected]> wrote:
>
> Replace the single skb pointer in an audit_buffer with
> a list of skb pointers. Add the audit_stamp information
> to the audit_buffer as there's no guarantee that there
> will be an audit_context containing the stamp associated
> with the event. At audit_log_end() time create auxiliary
> records (none are currently defined) as have been added
> to the list.
>
> Suggested-by: Paul Moore <[email protected]>
> Signed-off-by: Casey Schaufler <[email protected]>
> ---
> kernel/audit.c | 62 +++++++++++++++++++++++++++++++-------------------
> 1 file changed, 39 insertions(+), 23 deletions(-)
I believe the audit_buffer_aux_new() and audit_buffer_aux_end()
functions from patch 26/29 belong in this patch, but otherwise it
looks okay to me.
Acked-by: Paul Moore <[email protected]>
--
paul-moore.com
On 4/18/22 07:59, Casey Schaufler wrote:
> Replace the single skb pointer in an audit_buffer with
> a list of skb pointers. Add the audit_stamp information
> to the audit_buffer as there's no guarantee that there
> will be an audit_context containing the stamp associated
> with the event. At audit_log_end() time create auxiliary
> records (none are currently defined) as have been added
> to the list.
>
> Suggested-by: Paul Moore <[email protected]>
> Signed-off-by: Casey Schaufler <[email protected]>
I agree with Paul that audit_buffer_aux_new() and
audit_buffer_aux_end() belong in this patch
> ---
> kernel/audit.c | 62 +++++++++++++++++++++++++++++++-------------------
> 1 file changed, 39 insertions(+), 23 deletions(-)
>
> diff --git a/kernel/audit.c b/kernel/audit.c
> index 6b6c089512f7..4d44c05053b0 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -197,8 +197,10 @@ static struct audit_ctl_mutex {
> * to place it on a transmit queue. Multiple audit_buffers can be in
> * use simultaneously. */
> struct audit_buffer {
> - struct sk_buff *skb; /* formatted skb ready to send */
> + struct sk_buff *skb; /* the skb for audit_log functions */
> + struct sk_buff_head skb_list; /* formatted skbs, ready to send */
> struct audit_context *ctx; /* NULL or associated context */
> + struct audit_stamp stamp; /* audit stamp for these records */
> gfp_t gfp_mask;
> };
>
> @@ -1765,10 +1767,13 @@ __setup("audit_backlog_limit=", audit_backlog_limit_set);
>
> static void audit_buffer_free(struct audit_buffer *ab)
> {
> + struct sk_buff *skb;
> +
> if (!ab)
> return;
>
> - kfree_skb(ab->skb);
> + while((skb = skb_dequeue(&ab->skb_list)))
> + kfree_skb(skb);
we still have and ab->skb can we have a debug check that its freed by walking the queue?
> kmem_cache_free(audit_buffer_cache, ab);
> }
>
> @@ -1784,8 +1789,12 @@ static struct audit_buffer *audit_buffer_alloc(struct audit_context *ctx,
> ab->skb = nlmsg_new(AUDIT_BUFSIZ, gfp_mask);
> if (!ab->skb)
> goto err;
> +
> + skb_queue_head_init(&ab->skb_list);
> + skb_queue_tail(&ab->skb_list, ab->skb);
> +
> if (!nlmsg_put(ab->skb, 0, 0, type, 0, 0))
> - goto err;
> + kfree_skb(ab->skb);
why is this no longer an error?
>
> ab->ctx = ctx;
> ab->gfp_mask = gfp_mask;
> @@ -1849,7 +1858,6 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
> int type)
> {
> struct audit_buffer *ab;
> - struct audit_stamp stamp;
>
> if (audit_initialized != AUDIT_INITIALIZED)
> return NULL;
> @@ -1904,14 +1912,14 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
> return NULL;
> }
>
> - audit_get_stamp(ab->ctx, &stamp);
> + audit_get_stamp(ab->ctx, &ab->stamp);
> /* cancel dummy context to enable supporting records */
> if (ctx)
> ctx->dummy = 0;
> audit_log_format(ab, "audit(%llu.%03lu:%u): ",
> - (unsigned long long)stamp.ctime.tv_sec,
> - stamp.ctime.tv_nsec/1000000,
> - stamp.serial);
> + (unsigned long long)ab->stamp.ctime.tv_sec,
> + ab->stamp.ctime.tv_nsec/1000000,
> + ab->stamp.serial);
>
> return ab;
> }
> @@ -2402,26 +2410,14 @@ int audit_signal_info(int sig, struct task_struct *t)
> }
>
> /**
> - * audit_log_end - end one audit record
> - * @ab: the audit_buffer
> - *
> - * We can not do a netlink send inside an irq context because it blocks (last
> - * arg, flags, is not set to MSG_DONTWAIT), so the audit buffer is placed on a
> - * queue and a kthread is scheduled to remove them from the queue outside the
> - * irq context. May be called in any context.
> + * __audit_log_end - enqueue one audit record
> + * @skb: the buffer to send
> */
> -void audit_log_end(struct audit_buffer *ab)
> +static void __audit_log_end(struct sk_buff *skb)
> {
> - struct sk_buff *skb;
> struct nlmsghdr *nlh;
>
> - if (!ab)
> - return;
> -
> if (audit_rate_check()) {
> - skb = ab->skb;
> - ab->skb = NULL;
> -
> /* setup the netlink header, see the comments in
> * kauditd_send_multicast_skb() for length quirks */
> nlh = nlmsg_hdr(skb);
> @@ -2432,6 +2428,26 @@ void audit_log_end(struct audit_buffer *ab)
> wake_up_interruptible(&kauditd_wait);
> } else
> audit_log_lost("rate limit exceeded");
> +}
> +
> +/**
> + * audit_log_end - end one audit record
> + * @ab: the audit_buffer
> + *
> + * We can not do a netlink send inside an irq context because it blocks (last
> + * arg, flags, is not set to MSG_DONTWAIT), so the audit buffer is placed on a
> + * queue and a kthread is scheduled to remove them from the queue outside the
> + * irq context. May be called in any context.
> + */
> +void audit_log_end(struct audit_buffer *ab)
> +{
> + struct sk_buff *skb;
> +
> + if (!ab)
> + return;
> +
> + while ((skb = skb_dequeue(&ab->skb_list)))
> + __audit_log_end(skb);
>
> audit_buffer_free(ab);
> }
On Mon, Apr 25, 2022 at 9:06 PM John Johansen
<[email protected]> wrote:
> On 4/18/22 07:59, Casey Schaufler wrote:
> > Replace the single skb pointer in an audit_buffer with
> > a list of skb pointers. Add the audit_stamp information
> > to the audit_buffer as there's no guarantee that there
> > will be an audit_context containing the stamp associated
> > with the event. At audit_log_end() time create auxiliary
> > records (none are currently defined) as have been added
> > to the list.
> >
> > Suggested-by: Paul Moore <[email protected]>
> > Signed-off-by: Casey Schaufler <[email protected]>
>
> I agree with Paul that audit_buffer_aux_new() and
> audit_buffer_aux_end() belong in this patch
>
>
> > ---
> > kernel/audit.c | 62 +++++++++++++++++++++++++++++++-------------------
> > 1 file changed, 39 insertions(+), 23 deletions(-)
> >
> > diff --git a/kernel/audit.c b/kernel/audit.c
> > index 6b6c089512f7..4d44c05053b0 100644
> > --- a/kernel/audit.c
> > +++ b/kernel/audit.c
> > @@ -197,8 +197,10 @@ static struct audit_ctl_mutex {
> > * to place it on a transmit queue. Multiple audit_buffers can be in
> > * use simultaneously. */
> > struct audit_buffer {
> > - struct sk_buff *skb; /* formatted skb ready to send */
> > + struct sk_buff *skb; /* the skb for audit_log functions */
> > + struct sk_buff_head skb_list; /* formatted skbs, ready to send */
> > struct audit_context *ctx; /* NULL or associated context */
> > + struct audit_stamp stamp; /* audit stamp for these records */
> > gfp_t gfp_mask;
> > };
> >
> > @@ -1765,10 +1767,13 @@ __setup("audit_backlog_limit=", audit_backlog_limit_set);
> >
> > static void audit_buffer_free(struct audit_buffer *ab)
> > {
> > + struct sk_buff *skb;
> > +
> > if (!ab)
> > return;
> >
> > - kfree_skb(ab->skb);
> > + while((skb = skb_dequeue(&ab->skb_list)))
> > + kfree_skb(skb);
>
> we still have and ab->skb can we have a debug check that its freed by walking the queue?
By definition ab->skb is always going to point at something on the
list, if it doesn't we are likely to have failures elsewhere. The
structure definition is private to kernel/audit.c and the
allocation/creation is handled by an allocator function which always
adds the new skb to the list so I think we're okay.
We could add additional checks, but with audit performance already a
hot topic I would prefer to draw the debug-check line at input coming
from outside the audit subsystem.
--
paul-moore.com
On 4/26/22 11:12, Paul Moore wrote:
> On Mon, Apr 25, 2022 at 9:06 PM John Johansen
> <[email protected]> wrote:
>> On 4/18/22 07:59, Casey Schaufler wrote:
>>> Replace the single skb pointer in an audit_buffer with
>>> a list of skb pointers. Add the audit_stamp information
>>> to the audit_buffer as there's no guarantee that there
>>> will be an audit_context containing the stamp associated
>>> with the event. At audit_log_end() time create auxiliary
>>> records (none are currently defined) as have been added
>>> to the list.
>>>
>>> Suggested-by: Paul Moore <[email protected]>
>>> Signed-off-by: Casey Schaufler <[email protected]>
>>
>> I agree with Paul that audit_buffer_aux_new() and
>> audit_buffer_aux_end() belong in this patch
>>
>>
>>> ---
>>> kernel/audit.c | 62 +++++++++++++++++++++++++++++++-------------------
>>> 1 file changed, 39 insertions(+), 23 deletions(-)
>>>
>>> diff --git a/kernel/audit.c b/kernel/audit.c
>>> index 6b6c089512f7..4d44c05053b0 100644
>>> --- a/kernel/audit.c
>>> +++ b/kernel/audit.c
>>> @@ -197,8 +197,10 @@ static struct audit_ctl_mutex {
>>> * to place it on a transmit queue. Multiple audit_buffers can be in
>>> * use simultaneously. */
>>> struct audit_buffer {
>>> - struct sk_buff *skb; /* formatted skb ready to send */
>>> + struct sk_buff *skb; /* the skb for audit_log functions */
>>> + struct sk_buff_head skb_list; /* formatted skbs, ready to send */
>>> struct audit_context *ctx; /* NULL or associated context */
>>> + struct audit_stamp stamp; /* audit stamp for these records */
>>> gfp_t gfp_mask;
>>> };
>>>
>>> @@ -1765,10 +1767,13 @@ __setup("audit_backlog_limit=", audit_backlog_limit_set);
>>>
>>> static void audit_buffer_free(struct audit_buffer *ab)
>>> {
>>> + struct sk_buff *skb;
>>> +
>>> if (!ab)
>>> return;
>>>
>>> - kfree_skb(ab->skb);
>>> + while((skb = skb_dequeue(&ab->skb_list)))
>>> + kfree_skb(skb);
>>
>> we still have and ab->skb can we have a debug check that its freed by walking the queue?
>
> By definition ab->skb is always going to point at something on the
> list, if it doesn't we are likely to have failures elsewhere. The
> structure definition is private to kernel/audit.c and the
> allocation/creation is handled by an allocator function which always
> adds the new skb to the list so I think we're okay.
>
yeah I got that eventually, though it wasn't immediately obvious
> We could add additional checks, but with audit performance already a
> hot topic I would prefer to draw the debug-check line at input coming
> from outside the audit subsystem.
>
and that is why I asked for a debug check. But its not a hard requirement
just a nice to have because I have been bitten by internal consistency
issues all to often.