Module Name: src
Committed By: riastradh
Date: Fri Mar 3 12:53:04 UTC 2023
Modified Files:
src/lib/libc/sys: mremap.2
Log Message:
mremap(2): Note MAP_REMAPDUP bug.
XXX pullup-10, unless we fix the bug first
To generate a diff of this commit:
cvs rdiff -u -r1.8 -r1.9 src/lib/libc/sys/mremap.2
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/lib/libc/sys/mremap.2
diff -u src/lib/libc/sys/mremap.2:1.8 src/lib/libc/sys/mremap.2:1.9
--- src/lib/libc/sys/mremap.2:1.8 Wed Mar 1 20:08:41 2023
+++ src/lib/libc/sys/mremap.2 Fri Mar 3 12:53:04 2023
@@ -1,4 +1,4 @@
-.\" $NetBSD: mremap.2,v 1.8 2023/03/01 20:08:41 riastradh Exp $
+.\" $NetBSD: mremap.2,v 1.9 2023/03/03 12:53:04 riastradh Exp $
.\"
.\" Copyright (c) 2007 Thomas Klausner and Joerg Sonnenberger
.\" All rights reserved.
@@ -231,3 +231,36 @@ system call appeared in
It was based on the code that supports
.Fn mremap
compatibility for Linux binaries.
+.Sh BUGS
+If a mapping is created by
+.Xr mmap 2
+with
+.Dv MAP_PRIVATE
+and then duplicated by
+.Nm
+with
+.Dv MAP_REMAPDUP ,
+calling
+.Xr fork 2
+destroys the coupling between the original and duplicate mapping.
+Workarounds:
+.Bl -dash
+.It
+Create the original mapping with
+.Dv MAP_SHARED .
+.It
+Use
+.Xr minherit 2
+with
+.Dv MAP_INHERIT_NONE
+on the writable mapping.
+.It
+Don't use
+.Xr fork 2 ;
+use
+.Xr posix_spawn 2 .
+.El
+.Pp
+See
+.%U https://gnats.NetBSD.org/55177
+for details.
