[PATCH -next,v2 0/2] Audit: fix warning and check priority early

[PATCH -next,v2 0/2] Audit: fix warning and check priority early

[Gaosheng Cui]

v2:
  audit: fix possible null-pointer dereference in audit_filter_rules
  audit: return early if the rule has a lower priority
v1:
  audit: return early if the rule has a lower priority

Gaosheng Cui (2):
  audit: fix possible null-pointer dereference in audit_filter_rules
  audit: return early if the rule has a lower priority

 kernel/auditsc.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

-- 
2.30.0

[PATCH -next,v2 1/2] audit: fix possible null-pointer dereference in audit_filter_rules

[Gaosheng Cui]

Fix this possible null-pointer dereference in audit_filter_rules.

If ctx is null, a null-pointer dereference will occur:
    case AUDIT_SADDR_FAM:
        if (ctx->sockaddr)
		...
	break;

audit_filter_rules() error: we previously assumed 'ctx' could be null

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
---
 kernel/auditsc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 4ba3b8573ff4..42d4a4320526 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -647,7 +647,7 @@ static int audit_filter_rules(struct task_struct *tsk,
 			result = audit_comparator(audit_loginuid_set(tsk), f->op, f->val);
 			break;
 		case AUDIT_SADDR_FAM:
-			if (ctx->sockaddr)
+			if (ctx && ctx->sockaddr)
 				result = audit_comparator(ctx->sockaddr->ss_family,
 							  f->op, f->val);
 			break;
-- 
2.30.0

[PATCH -next,v2 2/2] audit: return early if the rule has a lower priority

[Gaosheng Cui]

It is not necessary for audit_filter_rules() functions to check
audit fileds of the rule with a lower priority, and if we did,
there might be some unintended effects, such as the ctx->ppid
may be changed unexpectedly, so return early if the rule has
a lower priority.

Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
---
 kernel/auditsc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 42d4a4320526..b517947bfa48 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -470,6 +470,9 @@ static int audit_filter_rules(struct task_struct *tsk,
 	u32 sid;
 	unsigned int sessionid;
 
+	if (ctx && rule->prio <= ctx->prio)
+		return 0;
+
 	cred = rcu_dereference_check(tsk->cred, tsk == current || task_creation);
 
 	for (i = 0; i < rule->field_count; i++) {
@@ -737,8 +740,6 @@ static int audit_filter_rules(struct task_struct *tsk,
 	}
 
 	if (ctx) {
-		if (rule->prio <= ctx->prio)
-			return 0;
 		if (rule->filterkey) {
 			kfree(ctx->filterkey);
 			ctx->filterkey = kstrdup(rule->filterkey, GFP_ATOMIC);
-- 
2.30.0

Re: [PATCH -next,v2 1/2] audit: fix possible null-pointer dereference in audit_filter_rules

[Paul Moore]

On Wed, Oct 13, 2021 at 5:10 AM Gaosheng Cui <cuigaosheng1@huawei.com> wrote:
>
> Fix this possible null-pointer dereference in audit_filter_rules.

Thanks for fixing this, just a couple of small comments:

I think you can drop the description text below here, the code snippet
is just a duplicate of the code and the error message is pretty
obvious.

> If ctx is null, a null-pointer dereference will occur:
>     case AUDIT_SADDR_FAM:
>         if (ctx->sockaddr)
>                 ...
>         break;
>
> audit_filter_rules() error: we previously assumed 'ctx' could be null
>
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>

I would also add a Fixes tag, for example:

Fixes: bf361231c295 ("audit: add saddr_fam filter field")

> ---
>  kernel/auditsc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 4ba3b8573ff4..42d4a4320526 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -647,7 +647,7 @@ static int audit_filter_rules(struct task_struct *tsk,
>                         result = audit_comparator(audit_loginuid_set(tsk), f->op, f->val);
>                         break;
>                 case AUDIT_SADDR_FAM:
> -                       if (ctx->sockaddr)
> +                       if (ctx && ctx->sockaddr)
>                                 result = audit_comparator(ctx->sockaddr->ss_family,
>                                                           f->op, f->val);
>                         break;
> --
> 2.30.0

-- 
paul moore
www.paul-moore.com

Re: [PATCH -next,v2 2/2] audit: return early if the rule has a lower priority

[Paul Moore]

On Wed, Oct 13, 2021 at 5:10 AM Gaosheng Cui <cuigaosheng1@huawei.com> wrote:
>
> It is not necessary for audit_filter_rules() functions to check
> audit fileds of the rule with a lower priority, and if we did,
> there might be some unintended effects, such as the ctx->ppid
> may be changed unexpectedly, so return early if the rule has
> a lower priority.
>
> Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
> ---
>  kernel/auditsc.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)

Thanks for this patch, it looks reasonable to me but have you done any
testing with this patch?  If so, what have you done?

As a FYI, the audit-testsuite project lives here:
* https://github.com/linux-audit/audit-testsuite

> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 42d4a4320526..b517947bfa48 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -470,6 +470,9 @@ static int audit_filter_rules(struct task_struct *tsk,
>         u32 sid;
>         unsigned int sessionid;
>
> +       if (ctx && rule->prio <= ctx->prio)
> +               return 0;
> +
>         cred = rcu_dereference_check(tsk->cred, tsk == current || task_creation);
>
>         for (i = 0; i < rule->field_count; i++) {
> @@ -737,8 +740,6 @@ static int audit_filter_rules(struct task_struct *tsk,
>         }
>
>         if (ctx) {
> -               if (rule->prio <= ctx->prio)
> -                       return 0;
>                 if (rule->filterkey) {
>                         kfree(ctx->filterkey);
>                         ctx->filterkey = kstrdup(rule->filterkey, GFP_ATOMIC);
> --
> 2.30.0

-- 
paul moore
www.paul-moore.com

Re: [PATCH -next,v2 1/2] audit: fix possible null-pointer dereference in audit_filter_rules

[cuigaosheng]

Thanks for your review, and i have droped the redundant commit message 
and add a Fixes tag to the patch.

https://patchwork.kernel.org/project/linux-audit/patch/20211016072351.237745-2-cuigaosheng1@huawei.com/ 
<https://patchwork.kernel.org/project/linux-audit/patch/20211016072351.237745-2-cuigaosheng1@huawei.com/>

Gaosheng.

在 2021/10/14 5:12, Paul Moore 写道:
> On Wed, Oct 13, 2021 at 5:10 AM Gaosheng Cui <cuigaosheng1@huawei.com> wrote:
>> Fix this possible null-pointer dereference in audit_filter_rules.
> Thanks for fixing this, just a couple of small comments:
>
> I think you can drop the description text below here, the code snippet
> is just a duplicate of the code and the error message is pretty
> obvious.
>
>> If ctx is null, a null-pointer dereference will occur:
>>      case AUDIT_SADDR_FAM:
>>          if (ctx->sockaddr)
>>                  ...
>>          break;
>>
>> audit_filter_rules() error: we previously assumed 'ctx' could be null
>>
>> Reported-by: kernel test robot <lkp@intel.com>
>> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
>> Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
> I would also add a Fixes tag, for example:
>
> Fixes: bf361231c295 ("audit: add saddr_fam filter field")
>
>> ---
>>   kernel/auditsc.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
>> index 4ba3b8573ff4..42d4a4320526 100644
>> --- a/kernel/auditsc.c
>> +++ b/kernel/auditsc.c
>> @@ -647,7 +647,7 @@ static int audit_filter_rules(struct task_struct *tsk,
>>                          result = audit_comparator(audit_loginuid_set(tsk), f->op, f->val);
>>                          break;
>>                  case AUDIT_SADDR_FAM:
>> -                       if (ctx->sockaddr)
>> +                       if (ctx && ctx->sockaddr)
>>                                  result = audit_comparator(ctx->sockaddr->ss_family,
>>                                                            f->op, f->val);
>>                          break;
>> --
>> 2.30.0

Re: [PATCH -next,v2 2/2] audit: return early if the rule has a lower priority

[cuigaosheng]

I have done some testing with this patch, we have some testsuites to 
verify the

function of audit, and i will test it with the audit-testsuite.

Thanks.

Gaosheng

在 2021/10/14 5:15, Paul Moore 写道:
> On Wed, Oct 13, 2021 at 5:10 AM Gaosheng Cui <cuigaosheng1@huawei.com> wrote:
>> It is not necessary for audit_filter_rules() functions to check
>> audit fileds of the rule with a lower priority, and if we did,
>> there might be some unintended effects, such as the ctx->ppid
>> may be changed unexpectedly, so return early if the rule has
>> a lower priority.
>>
>> Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
>> ---
>>   kernel/auditsc.c | 5 +++--
>>   1 file changed, 3 insertions(+), 2 deletions(-)
> Thanks for this patch, it looks reasonable to me but have you done any
> testing with this patch?  If so, what have you done?
>
> As a FYI, the audit-testsuite project lives here:
> * https://github.com/linux-audit/audit-testsuite
>
>> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
>> index 42d4a4320526..b517947bfa48 100644
>> --- a/kernel/auditsc.c
>> +++ b/kernel/auditsc.c
>> @@ -470,6 +470,9 @@ static int audit_filter_rules(struct task_struct *tsk,
>>          u32 sid;
>>          unsigned int sessionid;
>>
>> +       if (ctx && rule->prio <= ctx->prio)
>> +               return 0;
>> +
>>          cred = rcu_dereference_check(tsk->cred, tsk == current || task_creation);
>>
>>          for (i = 0; i < rule->field_count; i++) {
>> @@ -737,8 +740,6 @@ static int audit_filter_rules(struct task_struct *tsk,
>>          }
>>
>>          if (ctx) {
>> -               if (rule->prio <= ctx->prio)
>> -                       return 0;
>>                  if (rule->filterkey) {
>>                          kfree(ctx->filterkey);
>>                          ctx->filterkey = kstrdup(rule->filterkey, GFP_ATOMIC);
>> --
>> 2.30.0