Let get_items_log_attrs take the start-of-text offset into account
...when interpreting item->offset values.
I ran into this when executing tests of recent LibreOffice master with ASan on Fedora 32 (with pango-1.44.7-2.fc32.x86_64), where one of the tests renders various dialogs with a Tamil localization and failed with
==97247==ERROR: AddressSanitizer: SEGV on unknown address 0x60b000210006 (pc 0x7fd6c5b22b54 bp 0x61d0004b4150 sp 0x7fff107a0d18 T0)
==97247==The signal is caused by a READ memory access.
#0 in g_utf8_get_char at ../glib/gutf8.c:319:37 (/lib64/libglib-2.0.so.0 +0x85b54)
#1 in break_indic at ../pango/break-indic.c:119:17 (/lib64/libpango-1.0.so.0 +0x1076d)
#2 in break_script at ../pango/break.c:1896:7 (/lib64/libpango-1.0.so.0 +0x1076d)
#3 in tailor_break at ../pango/break.c:1606:9 (/lib64/libpango-1.0.so.0 +0x147db)
#4 in pango_tailor_break at ../pango/break.c:1774:7 (/lib64/libpango-1.0.so.0 +0x147db)
#5 in get_items_log_attrs at ../pango/pango-layout.c:4032:7 (/lib64/libpango-1.0.so.0 +0x2729c)
#6 in pango_layout_check_lines at ../pango/pango-layout.c:4289:7 (/lib64/libpango-1.0.so.0 +0x2729c)
#7 in pango_layout_get_extents_internal at ../pango/pango-layout.c:2623:3 (/lib64/libpango-1.0.so.0 +0x29068)
#8 in gtk_label_get_measuring_layout at /usr/src/debug/gtk3-3.24.22-1.fc32.x86_64/gtk/gtklabel.c:3376:3 (/lib64/libgtk-3.so.0 +0x2454d0)
[...]
From some debugging, it smells like pango_layout_check_lines
calls
pango_itemize_with_base_dir
to compute state.items
that are relative to the
beginning of layout->text
, but then passes state.items
together with the
offset'ed start
into get_items_log_attrs
, so that the latter misinterpreted
the items' locations relative to the offset'ed start.
Just adding
g_assert (item->offset <= length);
g_assert (item->length <= length - item->offset);
to the original get_items_log_attrs
would make various tests in the meson test
suite fail, but which pass again with the complete fix, matching the above
speculation.