Re: [PATCH] kernel/groups.c: consider about NULL for 'group_info' in all related extern functions

Chen Gang
2013-09-03T05:24:25Z

Hello Maintainers:

Please help check this patch, when you have time.

If need a related test, please let me know, I should try (better to
provide some suggestions for test).

Thanks.

On 08/20/2013 11:03 AM, Chen Gang wrote:
>
> If this patch is correct, also need modify the man page for the return
> value of getgroups().
>
> Thanks.
>
> On 08/20/2013 11:01 AM, Chen Gang wrote:
>> groups_alloc() can return NULL for 'group_info', also group_search()
>> already considers about NULL for 'group_info', so can assume the caller
>> has right to use all related extern functions when 'group_info' is NULL.
>>
>> For groups_free(), need check NULL to match groups_alloc(), just like
>> kmalloc/free().
>>
>> For set_groups(), can allow the caller to set NULL parameter to new
>> 'cred'.
>>
>> For system call getgroups(), if 'cred->group_info' is NULL, need return
>> the related error code (no related data), also need change the related
>> man page ("man 2 getgroups") to complete the return value.
>>
>>
>> Signed-off-by: Chen Gang <gang.chen@asianux.com>
>> ---
>> kernel/groups.c | 14 +++++++++++---
>> 1 files changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/groups.c b/kernel/groups.c
>> index 6b2588d..a21a4ce 100644
>> --- a/kernel/groups.c
>> +++ b/kernel/groups.c
>> @@ -52,6 +52,9 @@ EXPORT_SYMBOL(groups_alloc);
>>
>> void groups_free(struct group_info *group_info)
>> {
>> + if (!group_info)
>> + return;
>> +
>> if (group_info->blocks[0] != group_info->small_block) {
>> int i;
>> for (i = 0; i < group_info->nblocks; i++)
>> @@ -163,9 +166,12 @@ int groups_search(const struct group_info
>> *group_info, kgid_t grp)
>> */
>> int set_groups(struct cred *new, struct group_info *group_info)
>> {
>> - put_group_info(new->group_info);
>> - groups_sort(group_info);
>> - get_group_info(group_info);
>> + if (new->group_info)
>> + put_group_info(new->group_info);
>> + if (group_info) {
>> + groups_sort(group_info);
>> + get_group_info(group_info);
>> + }
>> new->group_info = group_info;
>> return 0;
>> }
>> @@ -206,6 +212,8 @@ SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t
>> __user *, grouplist)
>>
>> if (gidsetsize < 0)
>> return -EINVAL;
>> + if (!cred->group_info)
>> + return -ENODATA;
>>
>> /* no need to grab task_lock here; it cannot change */
>> i = cred->group_info->ngroups;
>>
>
>

--
Chen Gang