We're using the same unbuffered input code as PolicyKit, polkitagenttextlistener.c -- I'm guessing that experiences the same bug on ppc64? I assume you can't reproduce this on any other architecture?

If termios.h isn't working, this points to a bigger bug with glibc. Reassigning....

Created attachment 1129774 [details]
test case

Richard,

Awesome test case. That's exactly what we need.

The code you posted is BE-unsafe, and ppc64 is a BE target.

 44                 gint c;
 45                 c = getc (tty);

This stores the value read from the tty in BE to an integer sized object.

 46                 if (c == '\n') {
 47                         /* ok, done */
 48                         break;
 49                 } else if (c == EOF) {
 50                         g_warning ("Got unexpected EOF.");
 51                         break;
 52                 } else {
 53                         g_string_append_len (str, (const gchar *) &c, 1);

The '&c' points to start of the integer sized object, which has a value of 0x0 for a character sized object e.g. { &c->[0x0], 0x0, 0x0, 0x59 'Y' }. This makes the code BE-unsafe.

To fix this requires a type conversion.

You need to do this:

                        gchar gc = (gchar) c;
                        g_string_append_len (str, (const gchar *) &gc, 1);

Knowing that `c` won't have a value of EOF, you can safely cast it to a gchar and convert the value (potentially loosing the value of the EOF, but you already checked for it earlier). Then the address of `gc` will point to the valid character value.

This is a somewhat classic BE-unsafe thing to do, which works fine on LE targets like x86_64 e.g. { &c->[0x59], 0x0, 0x0, 0x0}. This should also work fine on ppc64le.

You should audit your code for BE-unsafe operations like this since ppc64 is not going away any time soon.

Hi Carlos -- thanks for the detailed report, I learned a lesson today. Thanks!

Is this sort of BE-unsafe casting not getting flagged by compiler warnings or coverity checks ?

PolicyKit has the same bug so I filed it here: https://bugzilla.redhat.com/show_bug.cgi?id=1311648

commit 710a9445777793e49160587882860cbb7b43e311
Author: Richard Hughes <richard>
Date:   Mon May 16 15:27:35 2016 +0100

    Make pk_console_get_prompt() big endian safe
    
    Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1255079

I could remove and reinstall gpm-libs just with pkcon. Confirmation dialog works.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-2425.html