[regression] ubiquity crashed in debconf.py:104 with ValueError: invalid literal for int() with base 10: ''

StacktraceTop:
 XPending (dpy=0x1384000) at ../../src/Pending.c:55
 client_message_to_wire (event=0x7ffde5091650, ev=0x0) at ../../../../../gdk/x11/gdkasync.c:199
 _gdk_x11_send_client_message_async (display=<optimized out>, window=140728446031488, propagate=1935767139, event_mask=140728446031480, event_send=0x0, callback=0x1291c00, data=0x2939b9c) at ../../../../../gdk/x11/gdkasync.c:263
 ?? ()
 ?? ()

Steve, what makes you think it might be a glib issue?

Marking Incomplete for glib per the previous comment.

This bug has been reported on the Ubuntu ISO testing tracker.

A list of all reports related to this bug can be found here:
http://iso.qa.ubuntu.com/qatracker/reports/bugs/1751252

I am getting the same issue, same error. Crashes once I reach the progress screen of 18.04 installation.

Syslog report:

......

Apr 28 20:26:54 ubuntu localechooser: info: Set debian-installer/locale = 'en_CA.UTF-8'
Apr 28 20:26:54 ubuntu localechooser: info: System locale (debian-installer/locale) = 'en_CA.UTF-8'
Apr 28 20:26:54 ubuntu ubiquity: /usr/lib/ubiquity/localechooser/localechooser: 910: [: C.UTF-8: unexpected operator
Apr 28 20:26:54 ubuntu ubiquity[3103]: debconffilter_done: ubi-timezone (current: ubi-timezone)
Apr 28 20:26:54 ubuntu ubiquity[3103]: Step_before = stepLocation
Apr 28 20:26:54 ubuntu partman: mke2fs 1.44.1 (24-Mar-2018)
Apr 28 20:26:54 ubuntu ubiquity[3103]: switched to page usersetup
Apr 28 20:26:54 ubuntu clear_partitions: Considering /home,/dev/nvme0n1p6.
Apr 28 20:26:54 ubuntu kernel: [ 100.161039] EXT4-fs (nvme0n1p6): mounted filesystem with ordered data mode. Opts: (null)
Apr 28 20:26:54 ubuntu kernel: [ 100.278116] EXT4-fs (nvme0n1p7): mounted filesystem with ordered data mode. Opts: errors=remount-ro
Apr 28 20:26:54 ubuntu kernel: [ 100.296127] EXT4-fs (nvme0n1p6): mounted filesystem with ordered data mode. Opts: (null)
Apr 28 20:26:55 ubuntu ubiquity: File descriptor 3 (pipe:[67210]) leaked on pvs invocation. Parent PID 18458: /bin/sh
Apr 28 20:26:55 ubuntu ubiquity[3103]: debconffilter_done: ubiquity.components.partman_commit (current: ubi-usersetup)
Apr 28 20:26:55 ubuntu /install.py: keeping packages due to preseeding: icedtea6-plugin openoffice.org
Apr 28 20:26:55 ubuntu /install.py: keeping language packs for: en_US.UTF-8
Apr 28 20:26:56 ubuntu ubiquity: W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic/InRelease Could not resolve 'archive.ubuntu.com'
Apr 28 20:26:56 ubuntu ubiquity: W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/bionic-security/InRelease Could not resolve 'security.ubuntu.com'
Apr 28 20:26:56 ubuntu ubiquity: W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic-updates/InRelease Could not resolve 'archive.ubuntu.com'
Apr 28 20:26:56 ubuntu ubiquity: W: Some index files failed to download. They have been ignored, or old ones used instead.
Apr 28 20:26:56 ubuntu ubiquity: W: --force-yes is deprecated, use one of the options starting with --allow instead.
Apr 28 20:27:13 ubuntu ubiquity[3103]: debconffilter_done: ubi-usersetup (current: ubi-usersetup)
Apr 28 20:27:13 ubuntu ubiquity[3103]: Step_before = stepUserInfo
Apr 28 20:27:14 ubuntu kernel: [ 119.884166] do_trap: 26 callbacks suppressed
Apr 28 20:27:14 ubuntu kernel: [ 119.884168] traps: ubiquity[3103] trap int3 ip:7ff0a1502c41 sp:7ffe0681d810 error:0 in libglib-2.0.so.0.5600.1[7ff0a14b1000+113000]
Apr 28 20:27:25 ubuntu /install.py: Exception during installation:
Apr 28 20:27:25 ubuntu /install.py: Traceback (most recent call last):
Apr 28 20:27:25 ubuntu /install.py: File "/usr/share/ubiquity/install.py", line 765, in <module>
Apr 28 20:27:25 ubuntu /install.py: install.run()
Apr 28 20:27:25 ubuntu /install.py: File "/usr/share/ubiquity/install.py", line 135, in run
Apr 28 20:27:25 ubuntu /install.py: self.copy_all()
Apr 28 20:27:25 ubuntu /install.py: File "/usr/sha...

Also tracking in:
https://errors.ubuntu.com/problem/82f7f7e7923663c7b2123c7f1f49af29f6ff4d77
https://errors.ubuntu.com/problem/735a2b847e0eeab6c8a7b954de5110e43889be15

And my own crash from 18.04 final:

Apr 29 22:54:52 ubuntu ubiquity[3581]: debconffilter_done: ubi-usersetup (current: ubi-usersetup)
Apr 29 22:54:52 ubuntu ubiquity[3581]: Step_before = stepUserInfo
Apr 29 22:54:52 ubuntu kernel: do_trap: 28 callbacks suppressed
Apr 29 22:54:52 ubuntu kernel: traps: ubiquity[3581] trap int3 ip:7fd2ca14ec41 sp:7fffd3ffdfa0 error:0 in libglib-2.0.so.0.5600.1[7fd2ca0fd000+113000]
Apr 29 22:55:04 ubuntu /install.py[8718]: Exception during installation:
Apr 29 22:55:04 ubuntu /install.py[8718]: Traceback (most recent call last):
Apr 29 22:55:04 ubuntu /install.py[8718]: File "/usr/share/ubiquity/install.py", line 765, in <module>
Apr 29 22:55:04 ubuntu /install.py[8718]: install.run()
Apr 29 22:55:04 ubuntu /install.py[8718]: File "/usr/share/ubiquity/install.py", line 135, in run
Apr 29 22:55:04 ubuntu /install.py[8718]: self.copy_all()
Apr 29 22:55:04 ubuntu /install.py[8718]: File "/usr/share/ubiquity/install.py", line 513, in copy_all
Apr 29 22:55:04 ubuntu /install.py[8718]: self.db.progress('SET', 10 + copy_progress)
Apr 29 22:55:04 ubuntu /install.py[8718]: File "/usr/lib/python3/dist-packages/debconf.py", line 83, in <lambda>
Apr 29 22:55:04 ubuntu /install.py[8718]: lambda *args, **kw: self.command(command, *args, **kw))
Apr 29 22:55:04 ubuntu /install.py[8718]: File "/usr/lib/python3/dist-packages/debconf.py", line 104, in command
Apr 29 22:55:04 ubuntu /install.py[8718]: status = int(status)
Apr 29 22:55:04 ubuntu /install.py[8718]: ValueError: invalid literal for int() with base 10: ''
Apr 29 22:55:04 ubuntu /install.py[8718]:

The X error (from comment #3) is:

#3 0x00007f5a769377f7 in g_log_structured (log_domain=0x7f5a7365304e <_gdk_wayland_display_utf8_to_string_target+270> "f\220I\213U\bH\215J\001I;M\020s\"I\213u", log_level=G_LOG_LEVEL_ERROR) at ../../../../glib/gmessages.c:1768
        args = {{gp_offset = 48, fp_offset = 48, overflow_arg_area = 0x7ffde50913e8, reg_save_area = 0x7ffde50912d0}}
        buffer = "`\t\223\002\000\000\000\000\300\r\t\345\375\177\000\000\020\v\223\002\000\000\000\000\220\r\t\345\375\177\000\000\240\v\223\002\000\000\000\000`\r\t\345\375\177\000\000\360\t\223\002\000\000\000\000\060\r\t\345\375\177\000\000\200\n\223\002\000\000\000\000\000\r\t\345\375\177\000\000\000\000\000\000\000\000\000\000D\366\221vZ\177\000\000@\310\222\002\000\000\000\000\300\243R\002\000\000\000\000\200\254:\001\000\000\000\000\231\001\000\000\000\000\000\000\360\020\t\345\375\177\000\000P\022\t\345\375\177\000\000 z\222\002\000\000\000\000\000\224\221\002\000\000\000\000@7\351EZ\177\000\000\222T\302vZ\177\000\000\300\223fsZ\177\000\000\000\351\063o\366\363[%\000\000\000\000\000\000\000\000"...
        message_allocated = 0x118ebd0 "The program 'ubiquity' received an X Window System error.\nThis probably reflects a bug in the program.\nThe error was 'BadAccess (attempt to access private resource denied)'.\n (Details: serial 14686 e"...
        format = 0x1 <error: Cannot access memory at address 0x1>
        message = <optimized out>
        p = <optimized out>
        n_fields = 6
        i = 6
        stack_fields = {{key = 0x7f5a76982af1 "MESSAGE", value = 0x118ebd0, length = -1}, {key = 0x7f5a76982b04 "PRIORITY", value = 0x7f5a7697cc9a, length = -1}, {key = 0x7f5a76982b5e "GLIB_DOMAIN", value = 0x7f5a7365304e <_gdk_wayland_display_utf8_to_string_target+270>, length = -1}, {key = 0x7f5a736532a1 <data_source_dnd_finished+81> "\261%", value = 0x7f5a73671828 <__func__.67903+8>, length = -1}, {key = 0x7f5a73653281 <data_source_dnd_finished+49> "1\300\350\250\f\371\377H\213\065a\261%", value = 0x7f5a736712af, length = -1}, {key = 0x7f5a736532b3 <data_source_dnd_finished+99> "\017\037D", value = 0x7f5a73671f70 <__func__.66747+16>, length = -1}, {key = 0x0, value = 0x7ffde5090eb0, length = 140026516315808}, {key = 0x7f5a76c11192 <g_object_new_valist+258> "H\205\300H\211\301\017\204\312\003", value = 0x0, length = 0}, {key = 0x0, value = 0x7ffde5090eb0, length = 140026516315808}, {key = 0x7f5a76c11192 <g_object_new_valist+258> "H\205\300H\211\301\017\204\312\003", value = 0x7ffde5090eb0, length = 43252528}, {key = 0x293fb30 "\200\222\221\002", value = 0x7ffde5091000, length = 0}, {key = 0x0, value = 0x7ffde5090d00, length = 43190912}, {key = 0x2919280 "\002", value = 0x602c55ce0, length = 0}, {key = 0x0, value = 0x0, length = 0}, {key = 0x0, value = 0x0, length = 0}, {key = 0x0, value = 0x2932c50, length = 140728446029296}}
        fields = 0x7ffde5090d40
        fields_allocated = 0x0
        array = <optimized out>

Here's the crash with GDK_SYNCHRONIZE=1. It appears to be graphical. And I have a theory this maybe only happens on machines that default to hi-DPI (scale 200%) in the live session...

#6 0x00007fffef656c8d in _XError () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#7 0x00007fffef653bb7 in ?? () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#8 0x00007fffef653c75 in ?? () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#9 0x00007fffef654b88 in _XReply () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#10 0x00007fffef65057d in XSync () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#11 0x00007fffef65061b in ?? () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#12 0x00007fffef65760f in ?? () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#13 0x00007fffef40d7b7 in XShmAttach ()
   from /usr/lib/x86_64-linux-gnu/libXext.so.6
#14 0x00007fffef18b82b in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#15 0x00007fffef18c05e in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#16 0x00007fffef189c81 in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#17 0x00007fffef1868e8 in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#18 0x00007fffef16a585 in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
---Type <return> to continue, or q <return> to quit---
#19 0x00007fffef16a78c in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#20 0x00007fffef16ae28 in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#21 0x00007fffef10e021 in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#22 0x00007fffef157efc in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#23 0x00007fffef11657e in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#24 0x00007fffef10fb39 in ?? () from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#25 0x00007fffef108a55 in cairo_fill ()
   from /usr/lib/x86_64-linux-gnu/libcairo.so.2
#26 0x00007fffc2e66240 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#27 0x00007fffc1fd1e61 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#28 0x00007fffc2051a3b in ?? ()
   from /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#29 0x00007fffc1fdbbd1 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#30 0x00007fffc1fe1897 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#31 0x00007fffc1f4879f in ?? ()
   from /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#32 0x00007fffc1ccabde in ?? ()
   from /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#33 0x00007fffc1daeed2 in ?? ()
---Type <return> to continue, or q <return> to quit---
   from /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#34 0x00007fffc1cc67ab in ?? ()
   from /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#35 0x00007fffc1cc7095 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#36 0x00007fffc1005903 in WTF::RunLoop::performWork() ()
   from /usr/lib/x86_64-linux-gnu/libjavascriptcoregtk-4.0.so.18
#37 0x00007fffc102e959 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libjavascriptcoregtk-4.0.so.18
#38 0x00007ffff4b9e0f5 in g_main_context_dispatch ()
   from /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#39 0x00007ffff4b9e4c0 in ?? () from /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#40 0x00007ffff4b9e7d2 in g_main_loop_run ...

WORKAROUND:

1. Boot into the live session.
2. Settings > Devices > Displays > Scale = 100%
3. Click Apply.
4. Proceed with installation: Click "Install Ubuntu 18.04 LTS".

Stack trace with debug symbols (mostly).

This looks odd. We start with a 16x16 icon upscaled to 32x32 (scale=200%) but the pixbuf_x/y offset seems to be negative (memory underrun?). Is that a faulty attempt at rendering 32x32 from 16x16 input?

#19 0x00007fffef158e83 in INT_cairo_surface_create_similar_image (other=<optimized out>, format=CAIRO_FORMAT_ARGB32, width=32, height=32) at ../../../../src/cairo-surface.c:595
#20 0x00007ffff18884bc in gdk_cairo_set_source_pixbuf (cr=cr@entry=0x1336800, pixbuf=pixbuf@entry=0x25fba40, pixbuf_x=-16, pixbuf_y=-16) at ../../../../gdk/gdkcairo.c:339
#21 0x00007fffec8bb784 in gtk_css_image_icon_theme_draw (image=<optimized out>, cr=0x1336800, width=<optimized out>, height=16)
    at ../../../../gtk/gtkcssimageicontheme.c:84
#22 0x00007fffec8b6db1 in _gtk_css_image_draw (image=0x11990c0, cr=0x1336800, width=16, height=16)
    at ../../../../gtk/gtkcssimage.c:239

Ignore comment #16. Negative offsets appear to be valid: https://developer.gnome.org/gdk3/stable/gdk3-Cairo-Interaction.html#gdk-cairo-set-source-pixbuf

Here's the offending source code up to the failing X call. I'm not so sure that the math is right (or how getting it wrong might trigger this bug)...

static cairo_xlib_shm_t *
_cairo_xlib_shm_pool_create(cairo_xlib_display_t *display,
                            size_t size, void **ptr)
{
    Display *dpy = display->display;
    cairo_xlib_shm_t *pool;
    size_t bytes, maxbits = 16, minbits = MIN_BITS;
    Status success;

    pool = malloc (sizeof (cairo_xlib_shm_t));
    if (pool == NULL)
        return NULL;

    bytes = 1 << maxbits;
    while (bytes <= size)
        bytes <<= 1, maxbits++;
    bytes <<= 3;

    minbits += (maxbits - 16) / 2;

    pool->shm.shmid = shmget (IPC_PRIVATE, bytes, IPC_CREAT | 0600);
    while (pool->shm.shmid == -1 && bytes >= 2*size) {
        bytes >>= 1;
        pool->shm.shmid = shmget (IPC_PRIVATE, bytes, IPC_CREAT | 0600);
    }
    if (pool->shm.shmid == -1)
        goto cleanup;

    pool->shm.readOnly = FALSE;
    pool->shm.shmaddr = shmat (pool->shm.shmid, NULL, 0);
    if (pool->shm.shmaddr == (char *) -1) {
        shmctl (pool->shm.shmid, IPC_RMID, NULL);
        goto cleanup;
    }

    pool->attached = XNextRequest (dpy);
    success = XShmAttach (dpy, &pool->shm);

Possibly worth noting is that size==4096 at scale 200%, and size==256 at scale 100%.

Correction:
Possibly worth noting is that size==4096 at scale 200%, and size==1024 at scale 100%.

It has been brought to my attention by a community user, that the workaround (change scale from 200% to 100%) found in comment#14 works.

On an Dell XPS 9360 with a 3200x1800 display it also defaults to 200% and I reliably reproduce this bug with the 18.04 final image.

I can confirm setting the scaling to 100% in the live session resolved the crash.

Here is the backtrace (bt f) with debug symbols.

I still have gdb open, if anyone needs me to do anything else?

According to this page, the problem possibly started in ubiquity version 18.04.11:
https://errors.ubuntu.com/problem/84a5563af3d2b85f098da832ece4cb8450bfd524

This one also started in version 18.04.11:
https://errors.ubuntu.com/problem/735a2b847e0eeab6c8a7b954de5110e43889be15

But this one started in 18.04.3:
https://errors.ubuntu.com/problem/82f7f7e7923663c7b2123c7f1f49af29f6ff4d77

Thanks @pjsingh5000. Your attachment shows the python stack ends at:

        # There's still work to do (postinstall). Let's keep the user
        # entertained.
        self.start_slideshow()
        Gtk.main()

Which agrees with what I see on screen when the bug occurs. It's the slideshow that never starts (or does, as a blank black/white image).

After that there is no debug info from comment #22. Although my attachment from comment #15 probably fills in the blanks: https://launchpadlibrarian.net/368099559/dbg.txt

So it looks like the bug here is entirely in the C code.

The BadAccess from ShmAttach is coming from the Xorg process somewhere in here:

static int
ProcShmAttach(ClientPtr client)
{
    SHMSTAT_TYPE buf;
    ShmDescPtr shmdesc;

    REQUEST(xShmAttachReq);

    REQUEST_SIZE_MATCH(xShmAttachReq);
    LEGAL_NEW_RESOURCE(stuff->shmseg, client);
    if ((stuff->readOnly != xTrue) && (stuff->readOnly != xFalse)) {
        client->errorValue = stuff->readOnly;
        return BadValue;
    }
    for (shmdesc = Shmsegs; shmdesc; shmdesc = shmdesc->next) {
        if (!SHMDESC_IS_FD(shmdesc) && shmdesc->shmid == stuff->shmid)
            break;
    }
    if (shmdesc) {
        if (!stuff->readOnly && !shmdesc->writable)
            return BadAccess;
        shmdesc->refcnt++;
    }
    else {
        shmdesc = malloc(sizeof(ShmDescRec));
        if (!shmdesc)
            return BadAlloc;
#ifdef SHM_FD_PASSING
        shmdesc->is_fd = FALSE;
#endif
        shmdesc->addr = shmat(stuff->shmid, 0,
                              stuff->readOnly ? SHM_RDONLY : 0);
        if ((shmdesc->addr == ((char *) -1)) || SHMSTAT(stuff->shmid, &buf)) {
            free(shmdesc);
            return BadAccess;
        }

        /* The attach was performed with root privs. We must
         * do manual checking of access rights for the credentials
         * of the client */

        if (shm_access(client, &(SHM_PERM(buf)), stuff->readOnly) == -1) {
            shmdt(shmdesc->addr);
            free(shmdesc);
            return BadAccess;
        }

        shmdesc->shmid = stuff->shmid;
        shmdesc->refcnt = 1;
        shmdesc->writable = !stuff->readOnly;
        shmdesc->size = SHM_SEGSZ(buf);
        shmdesc->next = Shmsegs;
        Shmsegs = shmdesc;
    }
    if (!AddResource(stuff->shmseg, ShmSegType, (void *) shmdesc))
        return BadAlloc;
    return Success;
}

Possibly relevant to permissions: The uid of this process changed from 'root' in 17.10 (where it works), to 'ubuntu' in 18.04 (where it doesn't work).

ubuntu 4468 17.8 1.2 502716 97352 tty1 Sl+ 08:17 0:01 /usr/bin/python3 /usr/lib/ubiquity/bin/ubiquity gtk_ui

In both cases the Xorg process is running as 'ubuntu'.

Getting closer. It's this failing in the Xorg process:

        /* The attach was performed with root privs. We must
         * do manual checking of access rights for the credentials
         * of the client */

        if (shm_access(client, &(SHM_PERM(buf)), stuff->readOnly) == -1) {
            shmdt(shmdesc->addr);
            free(shmdesc);
            return BadAccess;
        }

Unfortunately I can't tell what in shm_access is failing exactly because gdb skips straight from shm.c:314 back to the caller. So that suggests this code path, but I can't verify it:

static int
shm_access(ClientPtr client, SHMPERM_TYPE * perm, int readonly)
{
    int uid, gid;
    mode_t mask;
    int uidset = 0, gidset = 0;
    LocalClientCredRec *lcc;

    if (GetLocalClientCreds(client, &lcc) != -1) { // FALSE
    ...
    }
    /* Otherwise, check everyone else */
    mask = S_IROTH;
    if (!readonly) {
        mask |= S_IWOTH;
    }
    return (SHMPERM_MODE(perm) & mask) == mask ? 0 : -1;
}

So Xorg _should_ be returning an error, and it is. The problem seems to be that the client (python3 gtk_ui process) has a real uid=0 and effective uid=999. So that allows it to connect to Xorg (normally Xorg rejects root clients), but doesn't allow Xorg to check the client shm permissions. So Xorg rejects the client's attempt at XShmAttach.

How any of this relates to scale=200% and why it works at 100%, I'm not sure. We might need to review comment #15 in more detail.

Given that XShmAttach can fail (you can google the reasons), I think maybe we need to handle that in ubiquity/cairo and fall back to an alternative rendering method.

I'm not so sure we should be treating XShmAttach failure as a bug.

OK, I can now reproduce the problem at scale=100%. The trick is to slow down the installer with GDK_SYNCHRONIZE=1. So this is just a race condition, usually triggered by slower rendering of scale 200%, but can be triggered other ways.

So it sounds like a race between Xorg and the ubiquity perms dropping which then breaks Xorg's ability to authenticate XShmAttach used in cairo.

Ubiquity also crashes inside a virtual machine (VirtualBox) running on a non-HiDPI host machine.

I have observed corrupted graphics in the "main area" of Ubiquity when this bug occurs. By "main area", I am referring to the rendered rectangular area in Ubiquity below the title bar and above the "Copying files..." progress bar.

The corruption looks like jagged diagonal lines or "snow". I have seen this on both actual hardware (HiDPI machine scaled at 200%) and in a virtual machine (non-HiDPI hardware scaled at 100%).

I can reproduce this issue on xps13 9350. crash report is attached.

Please report crash files by running this command:

  ubuntu-bug YOURFILE.crash

Attaching them to bugs is not helpful to us, and a security risk to you.

A patch to fix the crash is here:
https://bugs.freedesktop.org/show_bug.cgi?id=98883#c6

If we fail to get cairo fixed for any reason, it's probably possible to do a workaround/fix in ubiquity. But I think there are now multiple reasons to fix cairo as first preference.

Fix for ubiquity proposed here: https://code.launchpad.net/~azzar1/ubiquity/+git/ubiquity/+merge/345056

I tried the patch for /usr/lib/ubiquity/ubiquity/misc.py in a virtual machine.

Instead of corrupted graphics in the Ubiquity window, I saw a blank white area above the "Copying files..." progress bar.

After a few seconds, the Ubiquity slide show appeared as usual, and I did *not* get a crash.

I will also try this on actual hardware.

You will get the same behaviour using the cairo fix too:
https://bugs.freedesktop.org/show_bug.cgi?id=98883#c6

The patch https://code.launchpad.net/~azzar1/ubiquity/+git/ubiquity/+merge/345056 did work for me on my mid-2017 MacBookPro (HW, not VM).

Thank you, Andrea!

An upload of ubiquity to bionic-proposed has been rejected from the upload queue for the following reason: "All looks good with the package itself, but sadly there seems to be some leftover .gladep file included with the changes. Could you reupload without it? Or, if it's needed, just mention that in the bug? Thank you!".

Ah, I'm sorry, I didn't see that there had been a bionic upload for this since the vcs was untouched and there was nothing in the unapproved queue... I just uploaded ubiquity for this to *cosmic* - not bionic yet. If it gets approved it should be in the next day's dailies and hopefully someone can test those to verify it's good.

Removed the .gladep file; it seems to have crept in by error during the git migration (also in my cosmic upload) and uploaded bionic. Thanks and sorry cyphermox if this treads on your toes.

This bug was fixed in the package ubiquity - 18.10.1

---------------
ubiquity (18.10.1) cosmic; urgency=medium

  [ Iain Lane ]
  * Bump sources to cosmic
  * Automatic update of included source packages: bterm-unifont 1.5,
    choose-mirror 2.78ubuntu4, preseed 1.71ubuntu8.

  [ Andrea Azzarone ]
  * misc.py: Restore the corrent euid in regain_privileges_save. Calling
    regain_privileges_save should restore the effective user-id to the one
    before the call to drop_privileges_save. We need to call os.setresuid and
    os.setresgid twice to avoid permission issues when calling os.setgroups.
    (LP: #1751252)

 -- Iain Lane <email address hidden> Tue, 08 May 2018 12:07:44 +0100

Hello Jean-Baptiste, or anyone else affected,

Accepted ubiquity into bionic-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/ubiquity/18.04.14.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed.Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested and change the tag from verification-needed-bionic to verification-done-bionic. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-bionic. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

I can confirm that the package version from bionic-proposed solves the problem.

During an installation I used Dell 2715Q with settings as in the screenshot attached (single monitor mode, 200% scaling).

# the updated package
apt policy ubiquity
ubiquity:
  Installed: 18.04.14.1
  Candidate: 18.04.14.1
  Version table:
 *** 18.04.14.1 500
        500 http://archive.ubuntu.com/ubuntu bionic-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     18.04.14 500
        500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages

Before adding "deb http://archive.ubuntu.com/ubuntu/ bionic-proposed main restricted" to sources.list and doing `apt install ubiquity` I had this in syslog:

ay 13 12:39:12 ubuntu ubiquity: W: --force-yes is deprecated, use one of the options starting with --allow instead.
May 13 12:39:12 ubuntu ubiquity[4617]: debconffilter_done: ubi-usersetup (current: ubi-usersetup)
May 13 12:39:12 ubuntu ubiquity[4617]: Step_before = stepUserInfo
May 13 12:39:12 ubuntu kernel: [ 249.861407] do_trap: 40 callbacks suppressed
May 13 12:39:12 ubuntu kernel: [ 249.861410] traps: ubiquity[4617] trap int3 ip:7fc1a36cdc41 sp:7ffe6a90a760 error:0 in libglib-2.0.so.0.5600.1[7fc1a367c000+113000]
May 13 12:39:21 ubuntu update-notifier[4223]: GtkDialog mapped without a transient parent. This is discouraged.
May 13 12:39:22 ubuntu /install.py: Exception during installation:
May 13 12:39:22 ubuntu /install.py: Traceback (most recent call last):
May 13 12:39:22 ubuntu /install.py: File "/usr/share/ubiquity/install.py", line 765, in <module>
May 13 12:39:22 ubuntu /install.py: install.run()
May 13 12:39:22 ubuntu /install.py: File "/usr/share/ubiquity/install.py", line 135, in run
May 13 12:39:22 ubuntu /install.py: self.copy_all()
May 13 12:39:22 ubuntu /install.py: File "/usr/share/ubiquity/install.py", line 513, in copy_all
May 13 12:39:22 ubuntu /install.py: self.db.progress('SET', 10 + copy_progress)
May 13 12:39:22 ubuntu /install.py: File "/usr/lib/python3/dist-packages/debconf.py", line 83, in <lambda>
May 13 12:39:22 ubuntu /install.py: lambda *args, **kw: self.command(command, *args, **kw))
May 13 12:39:22 ubuntu /install.py: File "/usr/lib/python3/dist-packages/debconf.py", line 104, in command
May 13 12:39:22 ubuntu /install.py: status = int(status)
May 13 12:39:22 ubuntu /install.py: ValueError: invalid literal for int() with base 10: ''

After the update a newly started installation went just fine.

Hi,

I do confirm proposed worked also for me on a Dell XPS 15 9530.

This bug was fixed in the package ubiquity - 18.04.14.1

---------------
ubiquity (18.04.14.1) bionic; urgency=medium

  [ Iain Lane ]
  * Update Vcs-* for git migration

  [ Andrea Azzarone ]
  * misc.py: Restore the corrent euid in regain_privileges_save. Calling
    regain_privileges_save should restore the effective user-id to the one
    before the call to drop_privileges_save. We need to call os.setresuid and
    os.setresgid twice to avoid permission issues when calling os.setgroups.
    (LP: #1751252)

 -- Iain Lane <email address hidden> Tue, 08 May 2018 15:22:49 +0100

The verification of the Stable Release Update for ubiquity has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.

For anyone looking for how to use this fix with the current Ubuntu 18.04 installation ISO, this page ( https://askubuntu.com/a/1040322/14601 ) has a good description how to use the patch produced above in Comment 37.

Untargetting from cairo/bionic, the ubiquity fix is enough there

In the Live Version on MacBook Pro 2015 (13 inches, Retina) I changed the 'Screen Scale' from 200% to 100%, settings > Device > Display, and solved!

an able to upgrade from 17.04 to 18.04

I think the fix is in Ubuntu 18.04.1 (not 18.04) so please use 18.04.1:

http://releases.ubuntu.com/18.04/