Date: Fri, 10 Jun 2016 16:47:28 +0200 From: Jilles Tjoelker <jilles@stack.nl> To: Mariusz Zaborski <oshogbo@FreeBSD.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r301572 - in head/lib/libcasper: libcasper services/cap_dns services/cap_grp services/cap_pwd services/cap_random services/cap_sysctl Message-ID: <20160610144728.GA85730@stack.nl> In-Reply-To: <201606080203.u5823rbD075793@repo.freebsd.org> References: <201606080203.u5823rbD075793@repo.freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Wed, Jun 08, 2016 at 02:03:53AM +0000, Mariusz Zaborski wrote: > Author: oshogbo > Date: Wed Jun 8 02:03:53 2016 > New Revision: 301572 > URL: https://svnweb.freebsd.org/changeset/base/301572 > Log: > Add flags to the Casper services. > CASPER_SERVICE_STDIO - Casper will not close the first three descriptors (stdin, > stdout and stderr) this can be helpful for debugging. > CASPER_SERVICE_FD - Capser will not close all other descriptors, this can > be useful for a filesystem service. This reminds me that there are some common cases where it is wrong to close descriptors you don't know about. The non-POSIX command diff <(cmd1) <(cmd2) that compares the outputs of the two commands, when executed with bash that was compiled with the full /dev/fd visible (as in poudriere), will actually run something like diff /dev/fd/63 /dev/fd/62 passing two file descriptors to pipes. When created by a shell, these pathnames will start with /dev/fd/, but people could create symlinks to these special files. > [snip] > +static void > +stdnull(void) > +{ > + int fd; > + > + fd = open(_PATH_DEVNULL, O_RDWR); > + if (fd == -1) > + errx(1, "Unable to open %s", _PATH_DEVNULL); > + > + if (setsid() == -1) > + errx(1, "Unable to detach from session"); There is an implicit assumption here that stdnull() is only called from a process that was forked off from here, since setsid() will not and cannot work when called from a process that is already a session leader. If the application is running from a shell, this setsid() will exclude the process from most signals, including terminal ^C/^\/^Z, kill % and hangups. More generally, this might make it more likely for the process to hang around indefinitely after the parent is gone. > + > + if (dup2(fd, STDIN_FILENO) == -1) > + errx(1, "Unable to cover stdin"); > + if (dup2(fd, STDOUT_FILENO) == -1) > + errx(1, "Unable to cover stdout"); > + if (dup2(fd, STDERR_FILENO) == -1) > + errx(1, "Unable to cover stderr"); > + > + close(fd); This was not broken by this commit, but fd should not be closed if it is equal to STDIN_FILENO, STDOUT_FILENO or STDERR_FILENO. > [snip] -- Jilles Tjoelker
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20160610144728.GA85730>