Re: [patch] staging: lustre: potential underflow in libcfs_kkuc_group_add()

[Frank Zago <fzago@cray.com>]

On 11/03/2015 05:28 PM, Simmons, James A. wrote:
>
>> My static checker says that "group" is a user controlled number that can
>> be negative leading to an array underflow.  I have looked at it, and I'm
>> not an expert enough in lustre to say for sure if it is really a bug.
>> Anyway, it's simple enough to make the variable unsigned which pleases
>> the static checker and makes it easier to audit.
>>
>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>
> Dmitry do you this this could be placed under place under LU-6303 or does a new ticket need to be open.
> I also CC Frank Zago who is very familiar with this code. To me it looks okay.
>
> diff --git a/drivers/staging/lustre/include/linux/libcfs/libcfs_kernelcomm.h b/drivers/staging/lustre/include/linux/libcfs/libcfs_kernelcomm.h
> index a989d26..41f3d81 100644
> --- a/drivers/staging/lustre/include/linux/libcfs/libcfs_kernelcomm.h
> +++ b/drivers/staging/lustre/include/linux/libcfs/libcfs_kernelcomm.h
> @@ -91,7 +91,7 @@ typedef int (*libcfs_kkuc_cb_t)(__u32 data, void *cb_arg);
>   /* Kernel methods */
>   int libcfs_kkuc_msg_put(struct file *fp, void *payload);
>   int libcfs_kkuc_group_put(int group, void *payload);
> -int libcfs_kkuc_group_add(struct file *fp, int uid, int group,
> +int libcfs_kkuc_group_add(struct file *fp, int uid, unsigned int group,
>   				 __u32 data);
>   int libcfs_kkuc_group_rem(int uid, int group);
>   int libcfs_kkuc_group_foreach(int group, libcfs_kkuc_cb_t cb_func,
> diff --git a/drivers/staging/lustre/lustre/libcfs/kernel_user_comm.c b/drivers/staging/lustre/lustre/libcfs/kernel_user_comm.c
> index ad661a3..d8230ae 100644
> --- a/drivers/staging/lustre/lustre/libcfs/kernel_user_comm.c
> +++ b/drivers/staging/lustre/lustre/libcfs/kernel_user_comm.c
> @@ -110,7 +110,8 @@ static DECLARE_RWSEM(kg_sem);
>    * @param uid identifier for this receiver
>    * @param group group number
>    */
> -int libcfs_kkuc_group_add(struct file *filp, int uid, int group, __u32 data)
> +int libcfs_kkuc_group_add(struct file *filp, int uid, unsigned int group,
> +			  __u32 data)
>   {
>   	struct kkuc_reg *reg;

Yes, but for consistency, all 4 functions should be changed.

Regards,
   Frank.