PR/60275 CVS commit: src/bin/sh

["Robert Elz" <kre%netbsd.org@localhost>]

The following reply was made to PR bin/60275; it has been noted by GNATS.

From: "Robert Elz" <kre%netbsd.org@localhost>
To: gnats-bugs%gnats.NetBSD.org@localhost
Cc: 
Subject: PR/60275 CVS commit: src/bin/sh
Date: Wed, 20 May 2026 00:50:00 +0000

 Module Name:	src
 Committed By:	kre
 Date:		Wed May 20 00:50:00 UTC 2026
 
 Modified Files:
 	src/bin/sh: eval.c eval.h trap.c
 
 Log Message:
 PR bin/60275 discard some arriving signals
 
 The PR is only peripherally relevant to this, but it is all much
 the same problem, over a fork() trapped signals are maintained,
 and sh does not really want that.
 
 In this case, when there is a vfork() a signal arriving for a
 child (whether or not it should arrive and be processed) can be
 treated as if it arrived for the parent, and cause a trap action
 to be executed by the parent.   (Never observed to have happened,
 as best I am aware, but certainly looks as if it could.)
 
 Avoid that, by making sure that the child process never records
 a signal as having occurred, when it is being a vfork child
 (while the parent is sharing memory with it).
 
 Doing this meant making one variable that was previously local
 to eval.c globally visible (exposing it in eval.h), and then
 because the same name is used as a parameter in many other
 functions, changing the actual variable name (just to avoid
 potential compiler "shadowing" warnings) - which amounts to
 most of the actual change here.
 
 Then, make sure that variable is only ever set in the parent
 while signals are blocked (for the actual fix for this PR),
 so the parent in a signal handler will never see it set.
 
 In the signal handler, treat that variable, if set, as
 indicating that the child should not have received the signal
 (it should have been, and will be soon, reset to SIG_DFL)
 and continue to treat it as in the previous fix.   Under no
 circumstances record it as having been received, or the
 memory shared with the parent will cause the parent to later
 detect the signal as having been sent to it.
 
 Comments added explaining things where appropriate.
 
 
 To generate a diff of this commit:
 cvs rdiff -u -r1.198 -r1.199 src/bin/sh/eval.c
 cvs rdiff -u -r1.24 -r1.25 src/bin/sh/eval.h
 cvs rdiff -u -r1.60 -r1.61 src/bin/sh/trap.c
 
 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.