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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. (cherry picked from commit d524fa6c35e675eedbd8fe6cdf4db0b49c658026)