[PATCH xserver v2] xwayland: Don't process cursor warping without an xwl_seat

[Adam Jackson]

On Tue, 2018-02-06 at 12:41 -0500, Lyude Paul wrote:
> Unfortunately, on my machine Xwayland immediately crashes when I try to
> start it. gdb backtrace:
> 
>  #0  0x00007ffff74f0e79 in wl_proxy_marshal () from target:/lib64/libwayland-client.so.0
>  #1  0x0000000000413172 in zwp_confined_pointer_v1_destroy (zwp_confined_pointer_v1=0x700000000)
>      at hw/xwayland/Xwayland at exe/pointer-constraints-unstable-v1-client-protocol.h:612
>  #2  0x0000000000418bc0 in xwl_seat_destroy_confined_pointer (xwl_seat=0x8ba2a0)
>      at /home/lyudess/Projects/xserver/hw/xwayland/xwayland-input.c:2839
>  #3  0x0000000000418c09 in xwl_seat_unconfine_pointer (xwl_seat=0x8ba2a0)
>      at /home/lyudess/Projects/xserver/hw/xwayland/xwayland-input.c:2849
>  #4  0x0000000000410d97 in xwl_cursor_confined_to (device=0xa5a000, screen=0x8b9d80, window=0x9bdb70)
>      at /home/lyudess/Projects/xserver/hw/xwayland/xwayland.c:328
>  #5  0x00000000004a8571 in ConfineCursorToWindow (pDev=0xa5a000, pWin=0x9bdb70, generateEvents=1,
>      confineToScreen=0) at /home/lyudess/Projects/xserver/dix/events.c:900
>  #6  0x00000000004a94b7 in ScreenRestructured (pScreen=0x8b9d80)
>      at /home/lyudess/Projects/xserver/dix/events.c:1387
>  #7  0x0000000000502386 in RRScreenSizeNotify (pScreen=0x8b9d80)
>      at /home/lyudess/Projects/xserver/randr/rrscreen.c:160
>  #8  0x000000000041a83c in update_screen_size (xwl_output=0x8e7670, width=3840, height=2160)
>      at /home/lyudess/Projects/xserver/hw/xwayland/xwayland-output.c:203
>  #9  0x000000000041a9f0 in apply_output_change (xwl_output=0x8e7670)
>      at /home/lyudess/Projects/xserver/hw/xwayland/xwayland-output.c:252
>  #10 0x000000000041aaeb in xdg_output_handle_done (data=0x8e7670, xdg_output=0x8e7580)
>      at /home/lyudess/Projects/xserver/hw/xwayland/xwayland-output.c:307
>  #11 0x00007ffff50e9d1e in ffi_call_unix64 () at ../src/x86/unix64.S:76
>  #12 0x00007ffff50e968f in ffi_call (cif=<optimized out>, fn=<optimized out>, rvalue=<optimized out>,
>      avalue=<optimized out>) at ../src/x86/ffi64.c:525
>  #13 0x00007ffff74f3d8b in wl_closure_invoke () from target:/lib64/libwayland-client.so.0
>  #14 0x00007ffff74f0928 in dispatch_event.isra () from target:/lib64/libwayland-client.so.0
>  #15 0x00007ffff74f1be4 in wl_display_dispatch_queue_pending () from target:/lib64/libwayland-client.so.0
>  #16 0x00007ffff74f200b in wl_display_roundtrip_queue () from target:/lib64/libwayland-client.so.0
>  #17 0x0000000000418cad in InitInput (argc=12, argv=0x7fffffffd9c8)
>      at /home/lyudess/Projects/xserver/hw/xwayland/xwayland-input.c:2867
>  #18 0x00000000004a20e3 in dix_main (argc=12, argv=0x7fffffffd9c8, envp=0x7fffffffda30)
>      at /home/lyudess/Projects/xserver/dix/main.c:250
>  #19 0x0000000000420cb2 in main (argc=12, argv=0x7fffffffd9c8, envp=0x7fffffffda30)
>     at /home/lyudess/Projects/xserver/dix/stubmain.c:34
> 
> This appears to be the result of xwl_cursor_confined_to() and
> xwl_screen_get_default_seat(). While not against protocol, mutter ends
> up sending xdg_output before wl_seat. xwl_screen_get_default_seat()
> makes the naïve assumption that we always have a valid seat, we end up
> returning a pointer to the empty list itself instead of an actual seat
> and causing ourselves to segfault.
> 
> So, actually return NULL in xwl_screen_get_default_seat() if the seat
> list is empty, and skip any pointer confinement processing in
> xwl_cursor_confined_to() when we don't have a seat setup yet.
> 
> Signed-off-by: Lyude Paul <lyude at redhat.com>

remote: I: patch #202739 updated using rev 98edb9a35e2cdd61355656b82975d7f2b6a9f0e6.
remote: I: 1 patch(es) updated to state Accepted.
To ssh://git.freedesktop.org/git/xorg/xserver
   fd21b282dc..98edb9a35e  master -> master

- ajax