libnvme: nbft: reject heap objects too small for the structures they decode

[prabhakarpujeri]

Problem

Port of linux-nvme/libnvme#1125 to libnvme3.

The SSNS extended-info descriptor now validates its disclosed length (good), but three heap-object reads can still overrun:

1. read_hfi_info_tcp() dereferences the trinfo heap object as a full struct nbft_hfi_info_tcp (flags, mac, addresses, …) without verifying the object's declared length covers even the fields read unconditionally.
2. the SSNS subsys_traddr_obj is handed to format_ip_addr(), which always memcpy()s a 16-byte struct in6_addr regardless of the declared object length.
3. the newer HFI trinfo_version >= 2 ext-info object is dereferenced/read via read_hfi_info_dhcp() with the same under-declared trap.

get_heap_obj() validates only heap containment (in_heap) plus string NUL-termination; a file can point a struct-typed heap object at heap_end - 2 and later reads walk past the heap.

Fix

• __get_heap_obj() gains a min_len parameter rejecting non-string heap objects shorter than the structure the caller dereferences.
• get_heap_obj() derives the minimum from the output pointer type via _Generic (strings, byte arrays, and the SSNS ext-info reader keep min 0 — the latter does its own spec-length check); call sites lose their (char **) casts.
• Explicit >= sizeof(struct in6_addr) check for the SSNS transport address before format_ip_addr().

Testing

• Full meson suite green (99 pass; crypto-util skip is env-related: no OpenSSL on this host, also on pristine master).
• Checked the NBFT fixture dumps are unchanged by the patch semantics (valid tables remain accepted; only under-sized heap objects — never correctly decodable — are rejected).

[igaw]

droped the reference to libnvme 1.

Didn't know about _Generic, nice C11 feature BUT we only require gnu99 as min version.

[igaw]

I am taking care of the patch, please don't update it.

I don't have a problem to update the min requirement for the compiler. As far I can tell all major distro ship compilers which are able to deal with C11. And if not, it's about time to update.

[igaw]

Thanks!