perf symbols: Add bounds checks to elf_read_build_id() note iteration

perf symbols: Add bounds checks to elf_read_build_id() note iteration

elf_read_build_id() iterates ELF notes using pointer arithmetic
driven by n_namesz and n_descsz from the note headers.  Neither
the note header read nor the subsequent name/desc advances are
checked against the section boundary.  A malformed ELF file with
oversized note sizes causes out-of-bounds reads past the section
data buffer.

Add two bounds checks: verify the note header fits within the
remaining section data, and verify that namesz + descsz (after
alignment) fits before advancing the pointer.

Fixes: fd7a346ea292074e ("perf symbols: Filename__read_build_id should look at .notes section too")
Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>