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

Chen Gang
2013-08-20T03:04:04Z

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