Hi. I'm working with Gimp 2.3.17 and having a persistent crash when using levels or curves.
As far as I could test it, it happens on layers. If the file is a JPG or a PNG (with or without alpha) it works fine, but if you create a new file, place a layer using copy+paste or dragging a file (i.e. a transparent png) into a layer, if you use curves or levels, you get a crash. I've never had a crash like this in previous versions, and I have this all the time.

Steps to reproduce the bug: 1) create a new image.
2) open a transparent PNG
3) copy the image into a new layer in the image you just created 4) scale it down to make it fit
5) adjust curves or levels.
... crash.

Here's the debug output:

*** glibc detected *** gimp-2.3: realloc(): invalid pointer: 0x094b8100 *** ======= Backtrace: =========
/lib/tls/i686/cmov/libc.so.6(realloc+0x392)[0xb7534322] /usr/lib/libglib-2.0.so.0(g_realloc+0x3b)[0xb765718b] /usr/lib/libgobject-2.0.so.0(g_object_weak_ref+0x91)[0xb76d0db1] /usr/lib/libgobject-2.0.so.0(g_object_add_weak_pointer+0x5d)[0xb76d0ead] /usr/lib/libgdk-x11-2.0.so.0[0xb7ad0aeb] /usr/lib/libgdk-x11-2.0.so.0(_gdk_windowing_window_queue_antiexpose+0x35)[0xb7ad0c65] /usr/lib/libgdk-x11-2.0.so.0[0xb7ab855f] /usr/lib/libgdk-x11-2.0.so.0(gdk_window_process_all_updates+0x97)[0xb7ab8887] /usr/lib/libgtk-x11-2.0.so.0[0xb7bbca52] /usr/lib/libglib-2.0.so.0[0xb764e091] /usr/lib/libglib-2.0.so.0(g_main_context_dispatch+0x182)[0xb764fdf2] /usr/lib/libglib-2.0.so.0[0xb7652dcf] /usr/lib/libglib-2.0.so.0(g_main_loop_run+0x1a9)[0xb7653179] gimp-2.3[0x80674d9]
gimp-2.3[0x8068458]
/lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xdc)[0xb74deebc] gimp-2.3[0x80671d1]
======= Memory map: ========
08048000-083b8000 r-xp 00000000 08:01 961912 /usr/local/bin/gimp-2.3 083b8000-083cc000 rw-p 0036f000 08:01 961912 /usr/local/bin/gimp-2.3 083cc000-09592000 rw-p 083cc000 00:00 0 [heap] b0dd6000-b0de1000 r-xp 00000000 08:01 260672 /lib/libgcc_s.so.1 b0de1000-b0de2000 rw-p 0000a000 08:01 260672 /lib/libgcc_s.so.1 b0df4000-b0df8000 rw-p b0df4000 00:00 0 b0df8000-b0dfb000 r-xp 00000000 08:01 1307958 /usr/local/lib/gimp/2.0/modules/libcdisplay_lcms.so b0dfb000-b0dfc000 rw-p 00003000 08:01 1307958 /usr/local/lib/gimp/2.0/modules/libcdisplay_lcms.so b0dfc000-b0dfe000 rw-p b0dfc000 00:00 0 b0dfe000-b0dff000 ---p b0dfe000 00:00 0 b0dff000-b15ff000 rw-p b0dff000 00:00 0 b15ff000-b1600000 ---p b15ff000 00:00 0 b1600000-b1e25000 rw-p b1600000 00:00 0 b1e25000-b1f00000 ---p b1e25000 00:00 0 b1f01000-b1f10000 r-xp 00000000 08:01 260646 /lib/libbz2.so.1.0.3 b1f10000-b1f11000 rw-p 0000f000 08:01 260646 /lib/libbz2.so.1.0.3 b1f11000-b1f1e000 rw-p b1f11000 00:00 0 b1f1e000-b1f23000 rw-p b2fcb000 00:00 0 b1f23000-b1f53000 r-xp 00000000 08:01 815810 /usr/lib/libcroco-0.6.so.3.0.1
b1f53000-b1f56000 rw-p 0002f000 08:01 815810 /usr/lib/libcroco-0.6.so.3.0.1
b1f56000-b1f82000 r-xp 00000000 08:01 816064 /usr/lib/libgsf-1.so.114.0.3
b1f82000-b1f85000 rw-p 0002b000 08:01 816064 /usr/lib/libgsf-1.so.114.0.3
b1f85000-b1f86000 rw-p b1f85000 00:00 0 b1f86000-b1fb5000 r-xp 00000000 08:01 816330 /usr/lib/librsvg-2.so.2.16.0
b1fb5000-b1fb6000 rw-p 0002f000 08:01 816330 /usr/lib/librsvg-2.so.2.16.0
b1fb6000-b1fb7000 ---p b1fb6000 00:00 0 b1fb7000-b27b7000 rw-p b1fb7000 00:00 0 b27b7000-b27b8000 ---p b27b7000 00:00 0 b27b8000-b2fb8000 rw-p b27b8000 00:00 0 b2fb8000-b2fbf000 r-xp 00000000 08:01 815776 /usr/lib/libfam.so.0.0.0 b2fbf000-b2fc0000 rw-p 00006000 08:01 815776 /usr/lib/libfam.so.0.0.0 b2fc0000-b2fc6000 r-xp 00000000 08:01 260635 /lib/libacl.so.1.1.0 b2fc6000-b2fc7000 rw-p 00005000 08:01 260635 /lib/libacl.so.1.1.0 b2fc8000-b2fcf000 rw-p b2fc8000 00:00 0 b2fcf000-b2fd2000 r--p 00000000 08:01 1206606 /usr/share/locale-langpack/es/LC_MESSAGES/atk10.mo b2fd2000-b2fd9000 r--p 00000000 08:01 1206638 /usr/share/locale-langpack/es/LC_MESSAGES/libgnomeui-2.0.mo b2fd9000-b300f000 r-xp 00000000 08:01 260726 /lib/libsepol.so.1 b300f000-b3010000 rw-p 00035000 08:01 260726 /lib/libsepol.so.1 b3010000-b301a000 rw-p b3010000 00:00 0 b301a000-b301d000 r-xp 00000000 08:01 816046 /usr/lib/libgpg-error.so.0.3.0
b301d000-b301e000 rw-p 00002000 08:01 816046 /usr/lib/libgpg-error.so.0.3.0
b301e000-b306d000 r-xp 00000000 08:01 815929 /usr/lib/libgcrypt.so.11.2.2
b306d000-b306f000 rw-p 0004e000 08:01 815929 /usr/lib/libgcrypt.so.11.2.2
b306f000-b3083000 r-xp 00000000 08:01 816386 /usr/lib/libtasn1.so.3.0.6 b3083000-b3084000 rw-p 00013000 08:01 816386 /usr/lib/libtasn1.so.3.0.6 b3084000-b3144000 r-xp 00000000 08:01 815151 /usr/lib/libasound.so.2.0.0 b3144000-b3149000 rw-p 000bf000 08:01 81515gimp-2.3: terminated: Cancelado gez@ohweb02a:~$
(script-fu:6309): LibGimpBase-WARNING **: script-fu: wire_read(): error gez@ohweb02a:~$