kern/80130: [patch] sigprocmask erronously cleared on fork (5-STABLE and later)

Kostik Belousov konstantin.belousov at zoral.com.ua
Wed Apr 20 00:40:03 PDT 2005


>Number:         80130
>Category:       kern
>Synopsis:       [patch] sigprocmask erronously cleared on fork (5-STABLE and later)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Apr 20 07:40:02 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator:     Kostik Belousov
>Release:        5-STABLE
>Organization:
>Environment:
FreeBSD deviant.zoral.local 5.4-STABLE FreeBSD 5.4-STABLE #16: Tue Apr 12 11:06:01 EEST 2005 root at deviant.zoral.local:/usr/obj/usr/src/sys/DEVIANT  i386
>Description:
      After fork(), the 5-STABLE system sets the child process                        
blocked signal mask to 0 (let us account single-threaded processes only). I was under impression that signal mask                                            shall be inherited by the child process (according to SUSv3 and man fork). Inheritance _was_ the behaviour of 4-STABLE (there, p_sigmask belongs to struct proc and placed in the copied-on-fork part of the structure) and also seen on other UNIXes (e.g. Solaris).

It seems that needs of thread_schedule_upcall() to zero sigmask interfere with the needs of the fork1().                                                    I propose the trivial patch (against 5-STABLE) to fix the problems. It handles td_sigmask in the way similar to td_sigstk, that is also zeroed on _upcall(), as was done by davidxu at kern/kern_fork.c:1.209 rev.
>How-To-Repeat:
I send the letter to the freebsd-hackers at Apr 12, 2005 with the program that shows the problem, see

http://lists.freebsd.org/pipermail/freebsd-hackers/2005-April/011513.html


>Fix:
Index: kern/kern_fork.c
===================================================================
RCS file: /usr/local/arch/ncvs/src/sys/kern/kern_fork.c,v
retrieving revision 1.234.2.8
diff -U3 -r1.234.2.8 kern_fork.c
--- kern/kern_fork.c    27 Feb 2005 02:36:39 -0000      1.234.2.8
+++ kern/kern_fork.c    20 Apr 2005 07:27:00 -0000
@@ -472,6 +472,7 @@
            __rangeof(struct ksegrp, kg_startcopy, kg_endcopy));
 
        td2->td_sigstk = td->td_sigstk;
+       td2->td_sigmask = td->td_sigmask;
 
        /*
         * Duplicate sub-structures as needed.

>Release-Note:
>Audit-Trail:
>Unformatted:


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