netdev - Re: [PATCH 2/3] security: bpf: Add eBPF LSM hooks and security field to eBPF map

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Date:   Thu, 31 Aug 2017 15:17:40 -0700
From:   Chenbo Feng <fengc@...gle.com>
To:     Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:     Chenbo Feng <chenbofeng.kernel@...il.com>,
        linux-security-module@...r.kernel.org,
        Jeffrey Vander Stoep <jeffv@...gle.com>,
        netdev@...r.kernel.org, SELinux <Selinux@...ho.nsa.gov>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Lorenzo Colitti <lorenzo@...gle.com>
Subject: Re: [PATCH 2/3] security: bpf: Add eBPF LSM hooks and security field
 to eBPF map

On Thu, Aug 31, 2017 at 2:17 PM, Mimi Zohar <zohar@...ux.vnet.ibm.com> wrote:
> On Thu, 2017-08-31 at 13:56 -0700, Chenbo Feng wrote:
>> From: Chenbo Feng <fengc@...gle.com>
>>
>> Introduce a pointer into struct bpf_map to hold the security information
>> about the map. The actual security struct varies based on the security
>> models implemented. Place the LSM hooks before each of the unrestricted
>> eBPF operations, the map_update_elem and map_delete_elem operations are
>> checked by security_map_modify. The map_lookup_elem and map_get_next_key
>> operations are checked by securtiy_map_read.
>>
>> Signed-off-by: Chenbo Feng <fengc@...gle.com>
>> ---
>>  include/linux/bpf.h  |  3 +++
>>  kernel/bpf/syscall.c | 28 ++++++++++++++++++++++++++++
>>  2 files changed, 31 insertions(+)
>>
>> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
>> index b69e7a5869ff..ca3e6ff7091d 100644
>> --- a/include/linux/bpf.h
>> +++ b/include/linux/bpf.h
>> @@ -53,6 +53,9 @@ struct bpf_map {
>>       struct work_struct work;
>>       atomic_t usercnt;
>>       struct bpf_map *inner_map_meta;
>> +#ifdef CONFIG_SECURITY
>> +     void *security;
>> +#endif
>>  };
>>
>>  /* function argument constraints */
>> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
>> index 045646da97cc..b15580bcf3b1 100644
>> --- a/kernel/bpf/syscall.c
>> +++ b/kernel/bpf/syscall.c
>> @@ -279,6 +279,10 @@ static int map_create(union bpf_attr *attr)
>>       if (err)
>>               return -EINVAL;
>>
>> +     err = security_map_create();
>> +     if (err)
>> +             return -EACCES;
>
> Any reason not to just return err?
>
> Mimi
>
Nope... return err might be better. I will fix this in next version.

Thanks
Chenbo
>> +
>>       /* find map type and init map: hashtable vs rbtree vs bloom vs ... */
>>       map = find_and_alloc_map(attr);
>>       if (IS_ERR(map))
>> @@ -291,6 +295,10 @@ static int map_create(union bpf_attr *attr)
>>       if (err)
>>               goto free_map_nouncharge;
>>
>> +     err = security_post_create(map);
>> +     if (err < 0)
>> +             goto free_map;
>> +
>>       err = bpf_map_alloc_id(map);
>>       if (err)
>>               goto free_map;
>> @@ -410,6 +418,10 @@ static int map_lookup_elem(union bpf_attr *attr)
>>       if (IS_ERR(map))
>>               return PTR_ERR(map);
>>
>> +     err = security_map_read(map);
>> +     if (err)
>> +             return -EACCES;
>> +
>>       key = memdup_user(ukey, map->key_size);
>>       if (IS_ERR(key)) {
>>               err = PTR_ERR(key);
>> @@ -490,6 +502,10 @@ static int map_update_elem(union bpf_attr *attr)
>>       if (IS_ERR(map))
>>               return PTR_ERR(map);
>>
>> +     err = security_map_modify(map);
>> +     if (err)
>> +             return -EACCES;
>> +
>>       key = memdup_user(ukey, map->key_size);
>>       if (IS_ERR(key)) {
>>               err = PTR_ERR(key);
>> @@ -573,6 +589,10 @@ static int map_delete_elem(union bpf_attr *attr)
>>       if (IS_ERR(map))
>>               return PTR_ERR(map);
>>
>> +     err = security_map_modify(map);
>> +     if (err)
>> +             return -EACCES;
>> +
>>       key = memdup_user(ukey, map->key_size);
>>       if (IS_ERR(key)) {
>>               err = PTR_ERR(key);
>> @@ -616,6 +636,10 @@ static int map_get_next_key(union bpf_attr *attr)
>>       if (IS_ERR(map))
>>               return PTR_ERR(map);
>>
>> +     err = security_map_read(map);
>> +     if (err)
>> +             return -EACCES;
>> +
>>       if (ukey) {
>>               key = memdup_user(ukey, map->key_size);
>>               if (IS_ERR(key)) {
>> @@ -935,6 +959,10 @@ static int bpf_prog_load(union bpf_attr *attr)
>>       if (CHECK_ATTR(BPF_PROG_LOAD))
>>               return -EINVAL;
>>
>> +     err = security_prog_load();
>> +     if (err)
>> +             return -EACCES;
>> +
>>       if (attr->prog_flags & ~BPF_F_STRICT_ALIGNMENT)
>>               return -EINVAL;
>>
>