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mesg: avoid 'ttyname failed: Success' message 

The ttyname(3) can fail to access /dev/ path, and that will cause function
to fail without setting errno value with result of rather confusing error
message.  Lets start setting stdin permission via /proc when this happens as
a go-around, with hope kernel following symlink does not fail.  Ok, noted,
that hopes of symlink follow working are pretty slim.

Based on patch from Sami Kerola <kerolasa@iki.fi>.

Reference: https://github.com/lxc/lxd/issues/1724
Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Karel Zak 2019-05-27 13:07:12 +02:00
parent a6d9d23b5f
commit 2c864ba8fc
3 changed files with 17 additions and 5 deletions
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1
term-utils/Makemodule.am
View File

@ -54,6 +54,7 @@ endif
if BUILD_MESG
usrbin_exec_PROGRAMS += mesg
mesg_LDADD = $(LDADD) libcommon.la
dist_man_MANS += term-utils/mesg.1
mesg_SOURCES = term-utils/mesg.c
endif

4
term-utils/mesg.1
View File

@ -58,8 +58,8 @@ should be executed in your login scripts.
.PP
The
.B mesg
utility silently exits with error status 2 if the current standard error output does
not refer to the terminal. In this case execute
utility silently exits with error status 2 if not executed on terminal. In this
case execute
.B mesg
is pointless. The command line option \fB\-\-verbose\fR forces
mesg to print a warning in this situation. This behaviour has been introduced

17
term-utils/mesg.c
View File

@ -59,6 +59,8 @@
#include "nls.h"
#include "c.h"
#include "rpmatch.h"
#include "ttyutils.h"
#include "pathnames.h"
/* exit codes */
@ -90,6 +92,7 @@ int main(int argc, char *argv[])
{
struct stat sb;
char *tty;
char ttybuf[sizeof(_PATH_PROC_FDDIR) + sizeof(stringify_value(INT_MAX))];
int ch, fd, verbose = FALSE, ret;
static const struct option longopts[] = {
@ -121,13 +124,21 @@ int main(int argc, char *argv[])
argc -= optind;
argv += optind;
if (!isatty(STDERR_FILENO)) {
fd = get_terminal_stdfd();
if (fd < 0) {
if (verbose)
warnx(_("no tty"));
exit(MESG_EXIT_FAILURE);
}
if ((tty = ttyname(STDERR_FILENO)) == NULL)
err(MESG_EXIT_FAILURE, _("ttyname failed"));
tty = ttyname(fd);
if (!tty) {
snprintf(ttybuf, sizeof(ttybuf), "%s/%d", _PATH_PROC_FDDIR, fd);
tty = ttybuf;
if (verbose)
warnx(_("ttyname() failed, attempting to go around using: %s"), tty);
}
if ((fd = open(tty, O_RDONLY)) < 0)
err(MESG_EXIT_FAILURE, _("cannot open %s"), tty);
if (fstat(fd, &sb))