2019-04-19 18:50:16

by Wenwen Wang

Subject: [PATCH v2] audit: fix a memory leak bug

In audit_rule_change(), audit_data_to_entry() is firstly invoked to
translate the payload data to the kernel's rule representation. In
audit_data_to_entry(), depending on the audit field type, an audit tree may
be created in audit_make_tree(), which eventually invokes kmalloc() to
allocate the tree. Since this tree is a temporary tree, it will be then
freed in the following execution, e.g., audit_add_rule() if the message
type is AUDIT_ADD_RULE or audit_del_rule() if the message type is
AUDIT_DEL_RULE. However, if the message type is neither AUDIT_ADD_RULE nor
AUDIT_DEL_RULE, i.e., the default case of the switch statement, this
temporary tree is not freed.

To fix this issue, only allocate the tree when the type is AUDIT_ADD_RULE
or AUDIT_DEL_RULE.

Signed-off-by: Wenwen Wang <[email protected]>
---
kernel/auditfilter.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index 63f8b3f..923b858 100644
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -1114,22 +1114,28 @@ int audit_rule_change(int type, int seq, void *data, size_t datasz)
int err = 0;
struct audit_entry *entry;

- entry = audit_data_to_entry(data, datasz);
- if (IS_ERR(entry))
- return PTR_ERR(entry);
-
switch (type) {
case AUDIT_ADD_RULE:
+ entry = audit_data_to_entry(data, datasz);
+ if (IS_ERR(entry))
+ return PTR_ERR(entry);
+
err = audit_add_rule(entry);
audit_log_rule_change("add_rule", &entry->rule, !err);
break;
+
case AUDIT_DEL_RULE:
+ entry = audit_data_to_entry(data, datasz);
+ if (IS_ERR(entry))
+ return PTR_ERR(entry);
+
err = audit_del_rule(entry);
audit_log_rule_change("remove_rule", &entry->rule, !err);
break;
+
default:
- err = -EINVAL;
WARN_ON(1);
+ return -EINVAL;
}

if (err || type == AUDIT_DEL_RULE) {
--
2.7.4

2019-04-19 19:30:11

by Paul Moore

Subject: Re: [PATCH v2] audit: fix a memory leak bug

On Fri, Apr 19, 2019 at 11:10 AM Wenwen Wang <[email protected]> wrote:
>
> In audit_rule_change(), audit_data_to_entry() is firstly invoked to
> translate the payload data to the kernel's rule representation. In
> audit_data_to_entry(), depending on the audit field type, an audit tree may
> be created in audit_make_tree(), which eventually invokes kmalloc() to
> allocate the tree. Since this tree is a temporary tree, it will be then
> freed in the following execution, e.g., audit_add_rule() if the message
> type is AUDIT_ADD_RULE or audit_del_rule() if the message type is
> AUDIT_DEL_RULE. However, if the message type is neither AUDIT_ADD_RULE nor
> AUDIT_DEL_RULE, i.e., the default case of the switch statement, this
> temporary tree is not freed.
>
> To fix this issue, only allocate the tree when the type is AUDIT_ADD_RULE
> or AUDIT_DEL_RULE.
>
> Signed-off-by: Wenwen Wang <[email protected]>
> ---
> kernel/auditfilter.c | 16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)

This looks good, it just needs some minor vertical whitespace fixes (see below).

> diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
> index 63f8b3f..923b858 100644
> --- a/kernel/auditfilter.c
> +++ b/kernel/auditfilter.c
> @@ -1114,22 +1114,28 @@ int audit_rule_change(int type, int seq, void *data, size_t datasz)
> int err = 0;
> struct audit_entry *entry;
>
> - entry = audit_data_to_entry(data, datasz);
> - if (IS_ERR(entry))
> - return PTR_ERR(entry);
> -
> switch (type) {
> case AUDIT_ADD_RULE:
> + entry = audit_data_to_entry(data, datasz);
> + if (IS_ERR(entry))
> + return PTR_ERR(entry);
> +

I realize you are taking the blank line from the code above, but we
probably don't need it here.

> err = audit_add_rule(entry);
> audit_log_rule_change("add_rule", &entry->rule, !err);
> break;
> +

Definitely do not add this blank line.

> case AUDIT_DEL_RULE:
> + entry = audit_data_to_entry(data, datasz);
> + if (IS_ERR(entry))
> + return PTR_ERR(entry);
> +
> err = audit_del_rule(entry);
> audit_log_rule_change("remove_rule", &entry->rule, !err);
> break;
> +

Same here.

> default:
> - err = -EINVAL;
> WARN_ON(1);
> + return -EINVAL;
> }
>
> if (err || type == AUDIT_DEL_RULE) {
> --
> 2.7.4

--
paul moore
http://www.paul-moore.com

2019-04-20 01:48:27

by Wenwen Wang

Subject: Re: [PATCH v2] audit: fix a memory leak bug

On Fri, Apr 19, 2019 at 2:28 PM Paul Moore <[email protected]> wrote:
>
> On Fri, Apr 19, 2019 at 11:10 AM Wenwen Wang <[email protected]> wrote:
> >
> > In audit_rule_change(), audit_data_to_entry() is firstly invoked to
> > translate the payload data to the kernel's rule representation. In
> > audit_data_to_entry(), depending on the audit field type, an audit tree may
> > be created in audit_make_tree(), which eventually invokes kmalloc() to
> > allocate the tree. Since this tree is a temporary tree, it will be then
> > freed in the following execution, e.g., audit_add_rule() if the message
> > type is AUDIT_ADD_RULE or audit_del_rule() if the message type is
> > AUDIT_DEL_RULE. However, if the message type is neither AUDIT_ADD_RULE nor
> > AUDIT_DEL_RULE, i.e., the default case of the switch statement, this
> > temporary tree is not freed.
> >
> > To fix this issue, only allocate the tree when the type is AUDIT_ADD_RULE
> > or AUDIT_DEL_RULE.
> >
> > Signed-off-by: Wenwen Wang <[email protected]>
> > ---
> > kernel/auditfilter.c | 16 +++++++++++-----
> > 1 file changed, 11 insertions(+), 5 deletions(-)
>
> This looks good, it just needs some minor vertical whitespace fixes (see below).
>
> > diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
> > index 63f8b3f..923b858 100644
> > --- a/kernel/auditfilter.c
> > +++ b/kernel/auditfilter.c
> > @@ -1114,22 +1114,28 @@ int audit_rule_change(int type, int seq, void *data, size_t datasz)
> > int err = 0;
> > struct audit_entry *entry;
> >
> > - entry = audit_data_to_entry(data, datasz);
> > - if (IS_ERR(entry))
> > - return PTR_ERR(entry);
> > -
> > switch (type) {
> > case AUDIT_ADD_RULE:
> > + entry = audit_data_to_entry(data, datasz);
> > + if (IS_ERR(entry))
> > + return PTR_ERR(entry);
> > +
>
> I realize you are taking the blank line from the code above, but we
> probably don't need it here.
>
> > err = audit_add_rule(entry);
> > audit_log_rule_change("add_rule", &entry->rule, !err);
> > break;
> > +
>
> Definitely do not add this blank line.
>
> > case AUDIT_DEL_RULE:
> > + entry = audit_data_to_entry(data, datasz);
> > + if (IS_ERR(entry))
> > + return PTR_ERR(entry);
> > +
> > err = audit_del_rule(entry);
> > audit_log_rule_change("remove_rule", &entry->rule, !err);
> > break;
> > +
>
> Same here.
>
Thanks for your comments. I will remove the blank lines.

Wenwen