Re: [PATCH v6 07/10] ipc: add new SEM_SET command for sys_semctl() call

[Serge Hallyn <serge.hallyn@canonical.com>]

Quoting Stanislav Kinsbursky (skinsbursky@parallels.com):
> New SEM_SET command will be interpreted exactly as IPC_SET, but also will
> update key, cuid and cgid values. IOW, it allows to change existent key value.
> The fact, that key is not used is checked before update. Otherwise -EEXIST is
> returned.
> 
> Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>

Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>

(again, modulo requested /* fallthrough */ comment )

> ---
>  include/uapi/linux/sem.h   |    1 +
>  ipc/compat.c               |    1 +
>  ipc/sem.c                  |   10 ++++++++--
>  security/selinux/hooks.c   |    1 +
>  security/smack/smack_lsm.c |    1 +
>  5 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/include/uapi/linux/sem.h b/include/uapi/linux/sem.h
> index 541fce0..b6ae374 100644
> --- a/include/uapi/linux/sem.h
> +++ b/include/uapi/linux/sem.h
> @@ -18,6 +18,7 @@
>  /* ipcs ctl cmds */
>  #define SEM_STAT 18
>  #define SEM_INFO 19
> +#define SEM_SET  20
>  
>  /* Obsolete, used only for backwards compatibility and libc5 compiles */
>  struct semid_ds {
> diff --git a/ipc/compat.c b/ipc/compat.c
> index 9c70f9a..84d8efd 100644
> --- a/ipc/compat.c
> +++ b/ipc/compat.c
> @@ -290,6 +290,7 @@ static long do_compat_semctl(int first, int second, int third, u32 pad)
>  		break;
>  
>  	case IPC_SET:
> +	case SEM_SET:
>  		if (version == IPC_64) {
>  			err = get_compat_semid64_ds(&s64, compat_ptr(pad));
>  		} else {
> diff --git a/ipc/sem.c b/ipc/sem.c
> index 10e9085..3eac885 100644
> --- a/ipc/sem.c
> +++ b/ipc/sem.c
> @@ -1085,12 +1085,13 @@ static int semctl_down(struct ipc_namespace *ns, int semid,
>  	struct semid64_ds semid64;
>  	struct kern_ipc_perm *ipcp;
>  
> -	if(cmd == IPC_SET) {
> +	if (cmd == IPC_SET || cmd == SEM_SET) {
>  		if (copy_semid_from_user(&semid64, arg.buf, version))
>  			return -EFAULT;
>  	}
>  
> -	ipcp = ipcctl_pre_down(ns, &sem_ids(ns), semid, cmd,
> +	ipcp = ipcctl_pre_down(ns, &sem_ids(ns), semid,
> +			       (cmd != SEM_SET) ? cmd : IPC_SET,
>  			       &semid64.sem_perm, 0);
>  	if (IS_ERR(ipcp))
>  		return PTR_ERR(ipcp);
> @@ -1105,6 +1106,10 @@ static int semctl_down(struct ipc_namespace *ns, int semid,
>  	case IPC_RMID:
>  		freeary(ns, ipcp);
>  		goto out_up;
> +	case SEM_SET:
> +		err = ipc_update_key(&sem_ids(ns), &semid64.sem_perm, ipcp);
> +		if (err)
> +			break;
>  	case IPC_SET:
>  		err = ipc_update_perm(&semid64.sem_perm, ipcp);
>  		if (err)
> @@ -1152,6 +1157,7 @@ SYSCALL_DEFINE(semctl)(int semid, int semnum, int cmd, union semun arg)
>  		return err;
>  	case IPC_RMID:
>  	case IPC_SET:
> +	case SEM_SET:
>  		err = semctl_down(ns, semid, cmd, version, arg);
>  		return err;
>  	default:
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 78b77ac..02b037d 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -5133,6 +5133,7 @@ static int selinux_sem_semctl(struct sem_array *sma, int cmd)
>  		perms = SEM__DESTROY;
>  		break;
>  	case IPC_SET:
> +	case SEM_SET:
>  		perms = SEM__SETATTR;
>  		break;
>  	case IPC_STAT:
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index d51a8da..b4135ed 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -2253,6 +2253,7 @@ static int smack_sem_semctl(struct sem_array *sma, int cmd)
>  	case SETALL:
>  	case IPC_RMID:
>  	case IPC_SET:
> +	case SEM_SET:
>  		may = MAY_READWRITE;
>  		break;
>  	case IPC_INFO:
> 
> --
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