Re: [PATCH] nptl: fix block problem caused by setxid called from clone

[Gao feng <gaofeng at cn dot fujitsu dot com>]

On 11/08/2013 09:41 AM, Gao feng wrote:
> The process created by clone will have a copy of memory of
> parent process, if parent creates some thread before call
> clone, the stacked_used, __stack_user list is invalid for
> the child process created by clone. and if this child process
> runs before the threads, the setxid_futex of these threads
> will never be changed to 0 for this child process. since
> it only has a copied memory. so the setxid will be blocked
> by futex forever.
> 
> This patch skips operation of the threads in different thread
> group.
> 

Any comment?

> Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
> ---
>  nptl/allocatestack.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
> index 1e0fe1f..8fc2591 100644
> --- a/nptl/allocatestack.c
> +++ b/nptl/allocatestack.c
> @@ -1075,12 +1075,19 @@ __nptl_setxid (struct xid_command *cmdp)
>  
>    struct pthread *self = THREAD_SELF;
>  
> +  INTERNAL_SYSCALL_DECL (err);
> +  pid_t pid = INTERNAL_SYSCALL(getpid, err, 0);
> +
>    /* Iterate over the list with system-allocated threads first.  */
>    list_t *runp;
>    list_for_each (runp, &stack_used)
>      {
>        struct pthread *t = list_entry (runp, struct pthread, list);
> -      if (t == self)
> +      /* setxid may be called by the process created by clone,
> +       * this process has a copy of parent's memory but it is
> +       * running in different thread group, skip the threads
> +       * in different thread group. */
> +      if (t == self || t->pid != pid)
>  	continue;
>  
>        setxid_mark_thread (cmdp, t);
> @@ -1090,7 +1097,7 @@ __nptl_setxid (struct xid_command *cmdp)
>    list_for_each (runp, &__stack_user)
>      {
>        struct pthread *t = list_entry (runp, struct pthread, list);
> -      if (t == self)
> +      if (t == self || t->pid != pid)
>  	continue;
>  
>        setxid_mark_thread (cmdp, t);
> @@ -1106,7 +1113,7 @@ __nptl_setxid (struct xid_command *cmdp)
>        list_for_each (runp, &stack_used)
>  	{
>  	  struct pthread *t = list_entry (runp, struct pthread, list);
> -	  if (t == self)
> +	  if (t == self || t->pid != pid)
>  	    continue;
>  
>  	  signalled += setxid_signal_thread (cmdp, t);
> @@ -1115,7 +1122,7 @@ __nptl_setxid (struct xid_command *cmdp)
>        list_for_each (runp, &__stack_user)
>  	{
>  	  struct pthread *t = list_entry (runp, struct pthread, list);
> -	  if (t == self)
> +	  if (t == self || t->pid != pid)
>  	    continue;
>  
>  	  signalled += setxid_signal_thread (cmdp, t);
> @@ -1135,7 +1142,7 @@ __nptl_setxid (struct xid_command *cmdp)
>    list_for_each (runp, &stack_used)
>      {
>        struct pthread *t = list_entry (runp, struct pthread, list);
> -      if (t == self)
> +      if (t == self || t->pid != pid)
>  	continue;
>  
>        setxid_unmark_thread (cmdp, t);
> @@ -1144,7 +1151,7 @@ __nptl_setxid (struct xid_command *cmdp)
>    list_for_each (runp, &__stack_user)
>      {
>        struct pthread *t = list_entry (runp, struct pthread, list);
> -      if (t == self)
> +      if (t == self || t->pid != pid)
>  	continue;
>  
>        setxid_unmark_thread (cmdp, t);
> @@ -1152,7 +1159,7 @@ __nptl_setxid (struct xid_command *cmdp)
>  
>    /* This must be last, otherwise the current thread might not have
>       permissions to send SIGSETXID syscall to the other threads.  */
> -  INTERNAL_SYSCALL_DECL (err);
> +
>    result = INTERNAL_SYSCALL_NCS (cmdp->syscall_no, err, 3,
>  				 cmdp->id[0], cmdp->id[1], cmdp->id[2]);
>    if (INTERNAL_SYSCALL_ERROR_P (result, err))
>