Linkers group input note sections with the same name into one output
note section with the same name. One output note section is placed in
one PT_NOTE segment. Since new linkers merge input .note.gnu.property
sections into one output .note.gnu.property section, there is only
one NT_GNU_PROPERTY_TYPE_0 note in one PT_NOTE segment with new linkers.
Since older linkers treat input .note.gnu.property section as a generic
note section and just concatenate all input .note.gnu.property sections
into one output .note.gnu.property section without merging them, we may
see multiple NT_GNU_PROPERTY_TYPE_0 notes in one PT_NOTE segment with
older linkers.
When an older linker is used to created the program on CET-enabled OS,
the linker output has a single .note.gnu.property section with multiple
NT_GNU_PROPERTY_TYPE_0 notes, some of which have IBT and SHSTK enable
bits set even if the program isn't CET enabled. Such programs will
crash on CET-enabled machines. This patch updates the note parser:
1. Skip note parsing if a NT_GNU_PROPERTY_TYPE_0 note has been processed.
2. Check multiple NT_GNU_PROPERTY_TYPE_0 notes.
[BZ #23509]
* sysdeps/x86/dl-prop.h (_dl_process_cet_property_note): Skip
note parsing if a NT_GNU_PROPERTY_TYPE_0 note has been processed.
Update the l_cet field when processing NT_GNU_PROPERTY_TYPE_0 note.
Check multiple NT_GNU_PROPERTY_TYPE_0 notes.
* sysdeps/x86/link_map.h (l_cet): Expand to 3 bits, Add
lc_unknown.
d524fa6c35