illumos gate

usr/src/head/libelf.h defines struct Elf_Data like so:

/*
 * Data descriptor
 */
typedef struct {
    Elf_Void    *d_buf;
    Elf_Type    d_type;
    size_t        d_size;
    off_t        d_off;        /* offset into section */
    size_t        d_align;    /* alignment in section */
    unsigned    d_version;    /* elf version */
} Elf_Data;

elfdump uses these structures to cache various section data. Unfortunately there is insufficient checking on references (as I discovered in #7106).
d_buf is allowed to and can be NULL, primarily on corrupted or truncated binaries (as also seen in #6177).

In this ticket I endeavor to remove all of these insufficient checks from elfdump. I've attached another crashing sample. Unfortunately I do not have samples of all of these cases to verify they were fixed, but I believe the code is straightforward enough to show this through analysis.