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tty: Handle problem if line discipline does not have receive_buf 

Some tty line disciplines do not have a receive buf callback, so
properly check for that before calling it.  If they do not have this
callback, just eat the character quietly, as we can't fail this call.

Reported-by: Jann Horn <jannh@google.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Greg Kroah-Hartman 2019-01-20 10:46:58 +01:00
parent bfd8d8fe98
commit 27cfb3a53b
1 changed files with 2 additions and 1 deletions
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3
drivers/tty/tty_io.c
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@ -2189,7 +2189,8 @@ static int tiocsti(struct tty_struct *tty, char __user *p)
ld = tty_ldisc_ref_wait(tty); ld = tty_ldisc_ref_wait(tty);
if (!ld) if (!ld)
return -EIO; return -EIO;
ld->ops->receive_buf(tty, &ch, &mbz, 1); if (ld->ops->receive_buf)
ld->ops->receive_buf(tty, &ch, &mbz, 1);
tty_ldisc_deref(ld); tty_ldisc_deref(ld);
return 0; return 0;
} }