Re: + execve-must-clear-current-clear_child_tid.patch added to -mm tree

> From: Eric Dumazet <eric.dumazet@xxxxxxxxx>
>
> diff -puN fs/compat.c~execve-must-clear-current-clear_child_tid fs/compat.c
> --- a/fs/compat.c~execve-must-clear-current-clear_child_tid
> +++ a/fs/compat.c
> @@ -1550,6 +1550,7 @@ int compat_do_execve(char * filename,
>       mutex_unlock(&current->cred_guard_mutex);
>       acct_update_integrals(current);
>       free_bprm(bprm);
> +     current->clear_child_tid = NULL;
>       if (displaced)
>               put_files_struct(displaced);
>       return retval;
> diff -puN fs/exec.c~execve-must-clear-current-clear_child_tid fs/exec.c
> --- a/fs/exec.c~execve-must-clear-current-clear_child_tid
> +++ a/fs/exec.c
> @@ -1343,6 +1343,7 @@ int do_execve(char * filename,
>       mutex_unlock(&current->cred_guard_mutex);
>       acct_update_integrals(current);
>       free_bprm(bprm);
> +     current->clear_child_tid = NULL;
>       if (displaced)
>               put_files_struct(displaced);
>       return retval;

Perhaps it is better to change mm_release() ? It has to play with
->clear_child_tid anyway.

Oleg.

--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -568,18 +568,18 @@ void mm_release(struct task_struct *tsk,
         * the value intact in a core dump, and to save the unnecessary
         * trouble otherwise.  Userland only wants this done for a sys_exit.
         */
-       if (tsk->clear_child_tid
-           && !(tsk->flags & PF_SIGNALED)
-           && atomic_read(&mm->mm_users) > 1) {
-               u32 __user * tidptr = tsk->clear_child_tid;
+       if (tsk->clear_child_tid) {
+               if (!(tsk->flags & PF_SIGNALED) &&
+                   atomic_read(&mm->mm_users) > 1) {
+                       /*
+                        * We don't check the error code - if userspace has
+                        * not set up a proper pointer then tough luck.
+                        */
+                       put_user(0, tsk->clear_child_tid);
+                       sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
+                                       1, NULL, NULL, 0);
+               }
                tsk->clear_child_tid = NULL;
-
-               /*
-                * We don't check the error code - if userspace has
-                * not set up a proper pointer then tough luck.
-                */
-               put_user(0, tidptr);
-               sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
        }
 }
 

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