From 208faee14abf9152a5ea6b4f8f8c99a0be52cc18 Mon Sep 17 00:00:00 2001
From: Rob Browning <rlb@defaultvalue.org>
Date: Fri, 17 Jan 2025 11:45:26 -0600
Subject: fport_print: handle ttyname ENODEV
In some situations, ttyname may return ENODEV even though isatty is
true. From ttyname(3):
A process that keeps a file descriptor that refers to a pts(4) device
open when switching to another mount namespace that uses a different
/dev/ptmx instance may still accidentally find that a device path of
the same name for that file descriptor exists. However, this device
path refers to a different device and thus can't be used to access the
device that the file descriptor refers to. Calling ttyname() or
ttyname_r() on the file descriptor in the new mount namespace will
cause these functions to return NULL and set errno to ENODEV.
Observed in a Debian riscv64 porterbox schroot.
When ttyname fails with ENODEV, just include the file descriptor integer
value instead. Call ttyname() rather than scm_ttyname() to avoid some
extra work and having to catch the ENODEV.
* libguile/fports/c: include the integer fd when ttyname() fails with
ENODEV.
---
libguile/fports.c | 33 ++++++++++++++++++++++++++++++---
1 file changed, 30 insertions(+), 3 deletions(-)
diff --git a/libguile/fports.c b/libguile/fports.c
index 9d4ca6ace..267ed632f 100644
--- a/libguile/fports.c
+++ b/libguile/fports.c
@@ -554,6 +554,7 @@ SCM_DEFINE (scm_adjust_port_revealed_x, "adjust-port-revealed!", 2, 0, 0,
+#define FUNC_NAME "fport_print"
static int
fport_print (SCM exp, SCM port, scm_print_state *pstate SCM_UNUSED)
{
@@ -571,11 +572,36 @@ fport_print (SCM exp, SCM port, scm_print_state *pstate SCM_UNUSED)
fdes = (SCM_FSTREAM (exp))->fdes;
#if (defined HAVE_TTYNAME) && (defined HAVE_POSIX)
- if (isatty (fdes))
- scm_display (scm_ttyname (exp), port);
+ if (!isatty (fdes))
+ scm_intprint (fdes, 10, port);
else
-#endif /* HAVE_TTYNAME */
+ {
+ scm_i_scm_pthread_mutex_lock (&scm_i_misc_mutex);
+
+ char *name;
+ SCM_SYSCALL (name = ttyname (fdes));
+ int err = errno;
+ if (name != NULL)
+ name = strdup (name);
+
+ scm_i_pthread_mutex_unlock (&scm_i_misc_mutex);
+
+ if (name)
+ scm_display (scm_take_locale_string (name), port);
+ else
+ {
+ if (err == ENODEV)
+ scm_intprint (fdes, 10, port);
+ else
+ {
+ errno = err;
+ SCM_SYSERROR;
+ }
+ }
+ }
+#else /* can't use ttyname */
scm_intprint (fdes, 10, port);
+#endif
}
else
{
@@ -586,6 +612,7 @@ fport_print (SCM exp, SCM port, scm_print_state *pstate SCM_UNUSED)
scm_putc ('>', port);
return 1;
}
+#undef FUNC_NAME
/* fill a port's read-buffer with a single read. returns the first
char or EOF if end of file. */