CVS commit: src/bin/sh

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

Module Name:    src
Committed By:   kre
Date:           Wed Sep 15 18:29:45 UTC 2021

Modified Files:
        src/bin/sh: main.c parser.c redir.c redir.h

Log Message:
Improve the solution for the 2nd access to a fd which shouldn't
be available ("13") issue reported by Jan Schaumann on netbsd-users.

This fixes a bug in the earlier fix (a day or so ago) which could allow the
shell's idea of which fd range was in use by the script to get wildly
incorrect, but now also actually looks to see which fd's are in use as
renamed other user fd's during the lifetime of a redirection which needs
to be able to be undone (most redirections occur after a fork and are
permanent in the child process).   Attempting to access such a fd (as with
attempts to access a fd in use by the shell for its own purposes) is treated
as an attempt to access a closed fd (EBADF).  Attempting to reuse the fd
for some other purpose (which should be rare, even for scripts attempting
to cause problems, since the shell generally knows which fds the script
wants to use, and avoids them) will cause the renamed (renumbered) fd
to be renamed again (moved aside to some other available fd), just as
happens with the shell's private fds.

Also, when a generic fd is required, don't give up because of EMFILE
or similar unless there are no available fds at all (we might prefer >10
or bigger, but if there are none there, use anything).  This avoids
redirection errors when ulimit -n has been set small, and all the fds >10
that are available have been used, but we need somewhere to park the old
user of a fd while we reuse that fd for the redirection.


To generate a diff of this commit:
cvs rdiff -u -r1.85 -r1.86 src/bin/sh/main.c
cvs rdiff -u -r1.173 -r1.174 src/bin/sh/parser.c
cvs rdiff -u -r1.67 -r1.68 src/bin/sh/redir.c
cvs rdiff -u -r1.25 -r1.26 src/bin/sh/redir.h

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.