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Short description: Fedora-specific workaround for kernel pty bug.
Author(s): Fedora glibc team <glibc@lists.fedoraproject.org>
Origin: PATCH
Upstream status: not-submitted
This is a Fedora-specific workaround for a kernel bug where calling
ioctl on a pty will silently ignore the invalid c_cflag. The
workaround is to use TCGETS to verify the setting matches. This is
not upstream and needs to either be removed or submitted upstream
after analysis.
Index: b/sysdeps/unix/sysv/linux/tcsetattr.c
===================================================================
--- a/sysdeps/unix/sysv/linux/tcsetattr.c
+++ b/sysdeps/unix/sysv/linux/tcsetattr.c
@@ -45,6 +45,7 @@ __tcsetattr (int fd, int optional_action
{
struct __kernel_termios k_termios;
unsigned long int cmd;
+ int retval;
switch (optional_actions)
{
@@ -75,7 +76,36 @@ __tcsetattr (int fd, int optional_action
memcpy (&k_termios.c_cc[0], &termios_p->c_cc[0],
__KERNEL_NCCS * sizeof (cc_t));
- return INLINE_SYSCALL (ioctl, 3, fd, cmd, &k_termios);
+ retval = INLINE_SYSCALL (ioctl, 3, fd, cmd, &k_termios);
+
+ if (retval == 0 && cmd == TCSETS)
+ {
+ /* The Linux kernel has a bug which silently ignore the invalid
+ c_cflag on pty. We have to check it here. */
+ int save = errno;
+ retval = INLINE_SYSCALL (ioctl, 3, fd, TCGETS, &k_termios);
+ if (retval)
+ {
+ /* We cannot verify if the setting is ok. We don't return
+ an error (?). */
+ __set_errno (save);
+ retval = 0;
+ }
+ else if ((termios_p->c_cflag & (PARENB | CREAD))
+ != (k_termios.c_cflag & (PARENB | CREAD))
+ || ((termios_p->c_cflag & CSIZE)
+ && ((termios_p->c_cflag & CSIZE)
+ != (k_termios.c_cflag & CSIZE))))
+ {
+ /* It looks like the Linux kernel silently changed the
+ PARENB/CREAD/CSIZE bits in c_cflag. Report it as an
+ error. */
+ __set_errno (EINVAL);
+ retval = -1;
+ }
+ }
+
+ return retval;
}
weak_alias (__tcsetattr, tcsetattr)
libc_hidden_def (tcsetattr)