Linux: Support __IPC_64 in sysvctl *ctl command arguments

Old applications pass __IPC_64 as part of the command argument because
old glibc did not check for unknown commands, and passed through the
arguments directly to the kernel, without adding __IPC_64.
Applications need to continue doing that for old glibc compatibility,
so this commit enables this approach in current glibc.

For msgctl and shmctl, if no translation is required, make
direct system calls, as we did before the time64 changes.  If
translation is required, mask __IPC_64 from the command argument.

For semctl, the union-in-vararg argument handling means that
translation is needed on all architectures.

Tested on i686-linux-gnu, powerpc64le-linux-gnu, x86_64-linux-gnu.
Built with build-many-glibcs.py.

---
 sysdeps/unix/sysv/linux/ipc_priv.h |  6 ++++++
 sysdeps/unix/sysv/linux/msgctl.c   | 38 +++++++++++++++++++++++++-------------
 sysdeps/unix/sysv/linux/semctl.c   |  7 +++++++
 sysdeps/unix/sysv/linux/shmctl.c   | 38 +++++++++++++++++++++++++-------------
 4 files changed, 63 insertions(+), 26 deletions(-)


base-commit: 19934d629ee22bbd332f04da4320e4f624c9560c

* Florian Weimer via Libc-alpha:

> Old applications pass __IPC_64 as part of the command argument because
> old glibc did not check for unknown commands, and passed through the
> arguments directly to the kernel, without adding __IPC_64.
> Applications need to continue doing that for old glibc compatibility,
> so this commit enables this approach in current glibc.
>
> For msgctl and shmctl, if no translation is required, make
> direct system calls, as we did before the time64 changes.  If
> translation is required, mask __IPC_64 from the command argument.
>
> For semctl, the union-in-vararg argument handling means that
> translation is needed on all architectures.
>
> Tested on i686-linux-gnu, powerpc64le-linux-gnu, x86_64-linux-gnu.
> Built with build-many-glibcs.py.

I've filed a bug:

  Restore IPC_64 support in sysvipc *ctl functions
  <https://sourceware.org/bugzilla/show_bug.cgi?id=29771>

I'm going to reference it in the commit message.

Thanks,
Florian

On 08/11/22 12:00, Florian Weimer via Libc-alpha wrote:
> Old applications pass __IPC_64 as part of the command argument because
> old glibc did not check for unknown commands, and passed through the
> arguments directly to the kernel, without adding __IPC_64.
> Applications need to continue doing that for old glibc compatibility,
> so this commit enables this approach in current glibc.
> 
> For msgctl and shmctl, if no translation is required, make
> direct system calls, as we did before the time64 changes.  If
> translation is required, mask __IPC_64 from the command argument.
> 
> For semctl, the union-in-vararg argument handling means that
> translation is needed on all architectures.
> 
> Tested on i686-linux-gnu, powerpc64le-linux-gnu, x86_64-linux-gnu.
> Built with build-many-glibcs.py.

Sigh, another internal interface that bleed to userpace.  The fix sounds
reasonable to compatibility, just a typo below.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> 
> ---
>  sysdeps/unix/sysv/linux/ipc_priv.h |  6 ++++++
>  sysdeps/unix/sysv/linux/msgctl.c   | 38 +++++++++++++++++++++++++-------------
>  sysdeps/unix/sysv/linux/semctl.c   |  7 +++++++
>  sysdeps/unix/sysv/linux/shmctl.c   | 38 +++++++++++++++++++++++++-------------
>  4 files changed, 63 insertions(+), 26 deletions(-)
> 
> diff --git a/sysdeps/unix/sysv/linux/ipc_priv.h b/sysdeps/unix/sysv/linux/ipc_priv.h
> index 87893a6757..2f50c31a8e 100644
> --- a/sysdeps/unix/sysv/linux/ipc_priv.h
> +++ b/sysdeps/unix/sysv/linux/ipc_priv.h
> @@ -63,4 +63,10 @@ struct __old_ipc_perm
>  # define __IPC_TIME64 0
>  #endif
>  
> +#if __IPC_TIME64 || defined __ASSUME_SYSVIPC_BROKEN_MODE_T
> +# define IPC_CTL_NEED_TRANSLATION 1
> +#else
> +# define IPC_CTL_NEED_TRANSLATION 0
> +#endif
> +
>  #include <ipc_ops.h>
> diff --git a/sysdeps/unix/sysv/linux/msgctl.c b/sysdeps/unix/sysv/linux/msgctl.c
> index e824ebb095..67b43c0eff 100644
> --- a/sysdeps/unix/sysv/linux/msgctl.c
> +++ b/sysdeps/unix/sysv/linux/msgctl.c
> @@ -85,11 +85,19 @@ msgctl_syscall (int msqid, int cmd, msgctl_arg_t *buf)
>  int
>  __msgctl64 (int msqid, int cmd, struct __msqid64_ds *buf)
>  {
> -#if __IPC_TIME64
> +#if IPC_CTL_NEED_TRANSLATION
> +# if __IPC_TIME64
>    struct kernel_msqid64_ds ksemid, *arg = NULL;
> -#else
> +# else
>    msgctl_arg_t *arg;
> -#endif
> +# endif
> +
> +  /* Some applications pass the __IPC_64 flag in cmd, to invoke
> +     previously unsupported commands back when there was no EINVAL
> +     error checking in glibc.  Mask the flag for the switch statements
> +     below.  ,sgctl_syscall adds back the __IPC_64 flag for the actual

s/,sgctl_syscall/msgctl_syscall

> +     system call.  */
> +  cmd &= ~__IPC_64;
>  
>    switch (cmd)
>      {
> @@ -101,19 +109,19 @@ __msgctl64 (int msqid, int cmd, struct __msqid64_ds *buf)
>      case IPC_STAT:
>      case MSG_STAT:
>      case MSG_STAT_ANY:
> -#if __IPC_TIME64
> +# if __IPC_TIME64
>        if (buf != NULL)
>  	{
>  	  msqid64_to_kmsqid64 (buf, &ksemid);
>  	  arg = &ksemid;
>  	}
> -# ifdef __ASSUME_SYSVIPC_BROKEN_MODE_T
> +#  ifdef __ASSUME_SYSVIPC_BROKEN_MODE_T
>        if (cmd == IPC_SET)
>  	arg->msg_perm.mode *= 0x10000U;
> -# endif
> -#else
> +#  endif
> +# else
>        arg = buf;
> -#endif
> +# endif
>        break;
>  
>      case IPC_INFO:
> @@ -137,21 +145,25 @@ __msgctl64 (int msqid, int cmd, struct __msqid64_ds *buf)
>      case IPC_STAT:
>      case MSG_STAT:
>      case MSG_STAT_ANY:
> -#ifdef __ASSUME_SYSVIPC_BROKEN_MODE_T
> +# ifdef __ASSUME_SYSVIPC_BROKEN_MODE_T
>        arg->msg_perm.mode >>= 16;
> -#else
> +# else
>        /* Old Linux kernel versions might not clear the mode padding.  */
>        if (sizeof ((struct msqid_ds){0}.msg_perm.mode)
>            != sizeof (__kernel_mode_t))
>  	arg->msg_perm.mode &= 0xFFFF;
> -#endif
> +# endif
>  
> -#if __IPC_TIME64
> +# if __IPC_TIME64
>        kmsqid64_to_msqid64 (arg, buf);
> -#endif
> +# endif
>      }
>  
>    return ret;
> +
> +#else /* !IPC_CTL_NEED_TRANSLATION */
> +  return msgctl_syscall (msqid, cmd, buf);
> +#endif
>  }
>  #if __TIMESIZE != 64
>  libc_hidden_def (__msgctl64)
> diff --git a/sysdeps/unix/sysv/linux/semctl.c b/sysdeps/unix/sysv/linux/semctl.c
> index 77a8130c18..3458b018bc 100644
> --- a/sysdeps/unix/sysv/linux/semctl.c
> +++ b/sysdeps/unix/sysv/linux/semctl.c
> @@ -140,6 +140,13 @@ __semctl64 (int semid, int semnum, int cmd, ...)
>    union semun64 arg64 = { 0 };
>    va_list ap;
>  
> +  /* Some applications pass the __IPC_64 flag in cmd, to invoke
> +     previously unsupported commands back when there was no EINVAL
> +     error checking in glibc.  Mask the flag for the switch statements
> +     below.  semctl_syscall adds back the __IPC_64 flag for the actual
> +     system call.  */
> +  cmd &= ~__IPC_64;
> +
>    /* Get the argument only if required.  */
>    switch (cmd)
>      {
> diff --git a/sysdeps/unix/sysv/linux/shmctl.c b/sysdeps/unix/sysv/linux/shmctl.c
> index ea38935497..f00817a6f6 100644
> --- a/sysdeps/unix/sysv/linux/shmctl.c
> +++ b/sysdeps/unix/sysv/linux/shmctl.c
> @@ -85,11 +85,19 @@ shmctl_syscall (int shmid, int cmd, shmctl_arg_t *buf)
>  int
>  __shmctl64 (int shmid, int cmd, struct __shmid64_ds *buf)
>  {
> -#if __IPC_TIME64
> +#if IPC_CTL_NEED_TRANSLATION
> +# if __IPC_TIME64
>    struct kernel_shmid64_ds kshmid, *arg = NULL;
> -#else
> +# else
>    shmctl_arg_t *arg;
> -#endif
> +# endif
> +
> +  /* Some applications pass the __IPC_64 flag in cmd, to invoke
> +     previously unsupported commands back when there was no EINVAL
> +     error checking in glibc.  Mask the flag for the switch statements
> +     below.  shmctl_syscall adds back the __IPC_64 flag for the actual
> +     system call.  */
> +  cmd &= ~__IPC_64;
>  
>    switch (cmd)
>      {
> @@ -103,19 +111,19 @@ __shmctl64 (int shmid, int cmd, struct __shmid64_ds *buf)
>      case IPC_STAT:
>      case SHM_STAT:
>      case SHM_STAT_ANY:
> -#if __IPC_TIME64
> +# if __IPC_TIME64
>        if (buf != NULL)
>  	{
>  	  shmid64_to_kshmid64 (buf, &kshmid);
>  	  arg = &kshmid;
>  	}
> -# ifdef __ASSUME_SYSVIPC_BROKEN_MODE_T
> +#  ifdef __ASSUME_SYSVIPC_BROKEN_MODE_T
>        if (cmd == IPC_SET)
>          arg->shm_perm.mode *= 0x10000U;
> -# endif
> -#else
> +#  endif
> +# else
>        arg = buf;
> -#endif
> +# endif
>        break;
>  
>      case IPC_INFO:
> @@ -140,21 +148,25 @@ __shmctl64 (int shmid, int cmd, struct __shmid64_ds *buf)
>        case IPC_STAT:
>        case SHM_STAT:
>        case SHM_STAT_ANY:
> -#ifdef __ASSUME_SYSVIPC_BROKEN_MODE_T
> +# ifdef __ASSUME_SYSVIPC_BROKEN_MODE_T
>          arg->shm_perm.mode >>= 16;
> -#else
> +# else
>        /* Old Linux kernel versions might not clear the mode padding.  */
>        if (sizeof ((struct shmid_ds){0}.shm_perm.mode)
>  	  != sizeof (__kernel_mode_t))
>  	arg->shm_perm.mode &= 0xFFFF;
> -#endif
> +# endif
>  
> -#if __IPC_TIME64
> +# if __IPC_TIME64
>        kshmid64_to_shmid64 (arg, buf);
> -#endif
> +# endif
>      }
>  
>    return ret;
> +
> +#else /* !IPC_CTL_NEED_TRANSLATION */
> +  return shmctl_syscall (shmid, cmd, buf);
> +#endif
>  }
>  #if __TIMESIZE != 64
>  libc_hidden_def (__shmctl64)
> 
> base-commit: 19934d629ee22bbd332f04da4320e4f624c9560c
>

* Adhemerval Zanella Netto:

> On 08/11/22 12:00, Florian Weimer via Libc-alpha wrote:
>> Old applications pass __IPC_64 as part of the command argument because
>> old glibc did not check for unknown commands, and passed through the
>> arguments directly to the kernel, without adding __IPC_64.
>> Applications need to continue doing that for old glibc compatibility,
>> so this commit enables this approach in current glibc.
>> 
>> For msgctl and shmctl, if no translation is required, make
>> direct system calls, as we did before the time64 changes.  If
>> translation is required, mask __IPC_64 from the command argument.
>> 
>> For semctl, the union-in-vararg argument handling means that
>> translation is needed on all architectures.
>> 
>> Tested on i686-linux-gnu, powerpc64le-linux-gnu, x86_64-linux-gnu.
>> Built with build-many-glibcs.py.
>
> Sigh, another internal interface that bleed to userpace.  The fix sounds
> reasonable to compatibility, just a typo below.
>
> Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Thanks, pushed with the typo fix.

Florian