apparmor: Fix use-after-free in aa_audit_rule_init
diff mbox series

Message ID 20191017014619.26708-1-navid.emamdoost@gmail.com
State New
Headers show
Series
  • apparmor: Fix use-after-free in aa_audit_rule_init
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Commit Message

Navid Emamdoost Oct. 17, 2019, 1:46 a.m. UTC
In the implementation of aa_audit_rule_init(), when aa_label_parse()
fails the allocated memory for rule is released using
aa_audit_rule_free(). But after this release the the return statement
tries to access the label field of the rule which results in
use-after-free. Before releaseing the rule, copy errNo and return it
after releasing rule.

Fixes: 52e8c38001d8 ("apparmor: Fix memory leak of rule on error exit path")
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
---
 security/apparmor/audit.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Markus Elfring Oct. 20, 2019, 2:16 p.m. UTC | #1
> … But after this release the the return statement
> tries to access the label field of the rule which results in
> use-after-free. Before releaseing the rule, copy errNo and return it
> after releasing rule.

Please avoid a duplicate word and a typo in this change description.


…
> +++ b/security/apparmor/audit.c> @@ -197,8 +198,9 @@ int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
>  	rule->label = aa_label_parse(&root_ns->unconfined->label, rulestr,
>  				     GFP_KERNEL, true, false);
>  	if (IS_ERR(rule->label)) {
> +		err = rule->label;

How do you think about to define the added local variable in this if branch directly?

+		int err = rule->label;

>  		aa_audit_rule_free(rule);
> -		return PTR_ERR(rule->label);
> +		return PTR_ERR(err);
>  	}
>
>  	*vrule = rule;


Regards,
Markus
John Johansen Oct. 20, 2019, 6:49 p.m. UTC | #2
On 10/20/19 7:16 AM, Markus Elfring wrote:
>> … But after this release the the return statement
>> tries to access the label field of the rule which results in
>> use-after-free. Before releaseing the rule, copy errNo and return it
>> after releasing rule.
> 
Navid thanks for finding this, and Markus thanks for the review

> Please avoid a duplicate word and a typo in this change description.
> My preference would be a v2 version of the patch with the small clean-ups
that Markus has pointed out.

If I don't see a v2 this week I can pull this one in and do the revisions
myself adding a little fix-up note.

> 
> …
>> +++ b/security/apparmor/audit.c
> …
>> @@ -197,8 +198,9 @@ int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
>>  	rule->label = aa_label_parse(&root_ns->unconfined->label, rulestr,
>>  				     GFP_KERNEL, true, false);
>>  	if (IS_ERR(rule->label)) {
>> +		err = rule->label;
> 
> How do you think about to define the added local variable in this if branch directly?
> 
> +		int err = rule->label;
> 

yes, since err isn't defined or in use else where this would be preferable

>>  		aa_audit_rule_free(rule);
>> -		return PTR_ERR(rule->label);
>> +		return PTR_ERR(err);
>>  	}
>>
>>  	*vrule = rule;
> 
> 
> Regards,
> Markus
>
Navid Emamdoost Oct. 21, 2019, 3:25 p.m. UTC | #3
On Sun, Oct 20, 2019 at 1:51 PM John Johansen
<john.johansen@canonical.com> wrote:
>
> On 10/20/19 7:16 AM, Markus Elfring wrote:
> >> … But after this release the the return statement
> >> tries to access the label field of the rule which results in
> >> use-after-free. Before releaseing the rule, copy errNo and return it
> >> after releasing rule.
> >
> Navid thanks for finding this, and Markus thanks for the review
>
> > Please avoid a duplicate word and a typo in this change description.
> > My preference would be a v2 version of the patch with the small clean-ups
> that Markus has pointed out.

John and Markus, I updated and submitted v2.

>
> If I don't see a v2 this week I can pull this one in and do the revisions
> myself adding a little fix-up note.
>
> >
> > …
> >> +++ b/security/apparmor/audit.c
> > …
> >> @@ -197,8 +198,9 @@ int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
> >>      rule->label = aa_label_parse(&root_ns->unconfined->label, rulestr,
> >>                                   GFP_KERNEL, true, false);
> >>      if (IS_ERR(rule->label)) {
> >> +            err = rule->label;
> >
> > How do you think about to define the added local variable in this if branch directly?
> >
> > +             int err = rule->label;
> >
>
> yes, since err isn't defined or in use else where this would be preferable
>
> >>              aa_audit_rule_free(rule);
> >> -            return PTR_ERR(rule->label);
> >> +            return PTR_ERR(err);
> >>      }
> >>
> >>      *vrule = rule;
> >
> >
> > Regards,
> > Markus
> >
>

Patch
diff mbox series

diff --git a/security/apparmor/audit.c b/security/apparmor/audit.c
index 5a98661a8b46..48c15fb0aafe 100644
--- a/security/apparmor/audit.c
+++ b/security/apparmor/audit.c
@@ -178,6 +178,7 @@  void aa_audit_rule_free(void *vrule)
 int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
 {
 	struct aa_audit_rule *rule;
+	int err;
 
 	switch (field) {
 	case AUDIT_SUBJ_ROLE:
@@ -197,8 +198,9 @@  int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
 	rule->label = aa_label_parse(&root_ns->unconfined->label, rulestr,
 				     GFP_KERNEL, true, false);
 	if (IS_ERR(rule->label)) {
+		err = rule->label;
 		aa_audit_rule_free(rule);
-		return PTR_ERR(rule->label);
+		return PTR_ERR(err);
 	}
 
 	*vrule = rule;