Files
ci-libretro-fceumm/src/boards/vrc7.c
U-DESKTOP-SPFP6AQ\twistedtechre 1185db89c1 core: memory-safety, leak, and savestate-portability audit fixes
Squashed series of ~50 distinct bugs found during a multi-day
security/correctness audit, ranging from ROM-triggerable heap
corruption and savestate-triggered OOB read primitives down to
obscure cross-platform savestate breakage.

Build is clean on `make platform=unix` with zero new warnings.

CRITICAL (ROM-triggerable, exploitable on the user's machine)
=============================================================

* ines.c iNES 2.0 PRG/CHR exponent overflow leading to undersized
  allocation followed by heap buffer overflow on fread (pow() with
  attacker-chosen exponent up to 63). Cap exponent at 30 and
  compute size in uint32 with explicit cap below 2 GiB before
  storing in int.
* ines.c miscROMSize int wraparound from attacker-controlled PRG/
  CHR sizes; previous '& 0x8000000' check missed common underflow
  cases. Compute in int64 and reject <= 0 or > 128 MiB.
* unif.c MAPR chunk OOB heap read on chunks of size < 4. Validate
  chunk size before allocating board-name buffer.
* unif.c chunk size truncation: int conversion + missing cap allowed
  a 4 GiB chunk size to wrap. Cap at 16 MiB.
* unif.c FixRomSize infinite loop on size > 0x80000000. Cap input.
* unif.c DINF chunk: months[(m - 1) % 12] is UB for m==0; m comes
  from the .unf file. Clamp m into [1..12] before subtracting.
* unif.c NAME chunk: GameInfo->name = malloc(...) was unchecked.
* nsf.c size underflow: FCEU_fgetsize() - 0x80 wraps to ~UINT64_MAX
  on tiny files, propagating a huge size into uppow2/FCEU_malloc.
  Validate size > 0x80 before subtracting.
* nsf.c NSFMaxBank * 4096 cap tightened from 1<<20 (UB on signed-int
  overflow) to 1<<19 (fits in int).
* general.c uppow2 had signed-int UB (1 << 32) and wrapped to 0 for
  inputs near uint32 max. Cap at 0x80000000.
* cheat.c SubCheats[256] BSS overflow when more than 256 GG/PAR
  substitution cheats are active. The array is adjacent to MMapPtrs[64]
  in BSS which is exposed via retro_get_memory_data, making this
  overflow visible from outside the core.
* libretro.c retro_cheat_set strcpy stack overflow with arbitrary-
  length cheat strings from the frontend. Use strlcpy.

CRITICAL (savestate-triggerable on a malicious .fcs file)
=========================================================

* fds.c FDS savestate OOB read primitive: InDisk loaded from
  savestate is used as index into 8-element diskdata[] static
  pointer array. A value 8..254 dereferences arbitrary memory as
  a pointer (heap-read primitive). Also bounds-checked SelectDisk,
  mapperFDS_block, mapperFDS_blockstart, mapperFDS_diskaddr,
  mapperFDS_blocklen so blockstart+diskaddr stays within the 65500-
  byte disk buffer.
* 11 mappers had savestate-loaded variables masked at write time
  but not at restore time, used as indices into fixed arrays:
    - 88.c, KS7037.c, 112.c   cmd indexes reg[8]
    - sachen.c (S8259, S74LS374N) cmd indexes latch[8]
    - 357.c    dipswitch indexes outer_bank[4]
    - unrom512.c flash_state indexes erase_a/d/b[5]
    - 368.c    preg indexes banks[8]
    - 69.c     sndcmd indexes sreg[14]
    - mmc2and4.c latch0/latch1 index creg[4]
  None individually exploitable into RCE - the array writes corrupt
  adjacent BSS with constrained data flowing in - but each is an
  out-of-bounds read or write from attacker-controllable input.

HIGH (memory-safety, reachable on any load)
===========================================

* fceu-memory.c FCEU_malloc deref-of-NULL on allocation failure
  ('ret = 0; memset(ret, 0, size);').
* file.c multiple FCEUFILE/MakeMemWrap/MakeMemWrapBuffer unchecked
  allocations and unchecked filestream_tell return.
* libretro.c GameInfo NULL-derefs in three entry points
  (retro_set_controller_port_device, retro_get_memory_data,
  retro_get_memory_size) reachable on operations called before a
  successful load.
* libretro.c framebuffer leak ~256 KB per failed FCEUI_LoadGame
  (the libretro frontend doesn't call retro_unload_game on a
  failed load).
* libretro.c 3DS retro_deinit unchecked linearFree.
* libretro.c stereo / NTSC filter unchecked malloc returns.
* fceu.c FCEUI_LoadGame unchecked GameInfo malloc.
* fds.c SubLoad and FDSLoad unchecked FCEU_malloc on diskdatao
  backup buffers (NULL-deref in subsequent memcpy).
* fceu.c AllocGenieRW partial-failure leak: AReadG allocated but
  BWriteG malloc fails -> 256 KB leak per retry.
* input/bworld.c Update(): unbounded strcpy from attacker-supplied
  data into 20-byte bdata. Replaced with length-bounded copy.
* cart.c setprg2r/4r and setchr1r/2r/4r/8r mask-underflow guards.
  SetupCartPRGMapping/SetupCartCHRMapping compute (size >> N) - 1
  which underflows to 0xFFFFFFFF for chips smaller than the unit.
  setprg8r/16r/32r and setchr8r already had defensive size checks;
  the smaller units did not. malee.c (2 KB chip) and mapper 218
  (2 KB NTARAM-as-CHR) accidentally avoid OOB; the primitive is
  unsafe for any future board.
* video.c FCEU_InitVirtualVideo XBuf/XDBuf partial-failure leak.
* video.c, fceu.c FCEU_DispMessage / FCEU_printf / FCEU_PrintError:
  vsprintf into fixed stack buffers replaced with vsnprintf.
* core: validate magic-string read length on FDS/UNIF/NSF load
  (reject files too short to contain the magic so previous static
  buffer / stack garbage doesn't spuriously match).

LEAKS (every cart load/unload cycle)
====================================

* mmc5.c MMC5 cart-side: WRAM (up to 64K) + MMC5fill (1K) + ExRAM
  (1K) leaked per cycle. NSFMMC5_Close existed but was only used
  for NSF code path.
* onebus.c Mapper 270/436: 8 KB CHRRAM leaked per cycle.
* 330.c, 375.c, 528.c: 8 KB WRAM each, no Close at all.

CORRECTNESS (UB / ABI / endianness)
===================================

* fceu-endian.c FlipByteOrder loop bound was 'count' instead of
  'count/2', making it a no-op for every even count and silently
  breaking savestate portability for every FCEUSTATE_RLSB-marked
  field. The '#ifndef GEKKO' workarounds scattered through the
  codebase (sound.c, vrc7.c, vrc6.c) were symptoms of this root
  cause.
* state.c AddExState bounds check ran AFTER writing the entry, so
  when SFEXINDEX hit the 63-entry cap the next call would write
  the entry then immediately overwrite it with the terminator.
* state.c FCEUSS_Save_Mem: post-save callback was guarded by
  'if (SPreSave)' instead of 'if (SPostSave)'.
* Sequence-point UB in counter expressions across 4 board files,
  e.g. 'x = !x ? a : --x' and 'x = ++x % n'. GCC -Wsequence-point
  flags all five sites (285.c, 413.c, asic_mmc3.c, jyasic.c).
* SFORMAT size mismatches between declared variable type and
  AddExState size argument:
    - asic_vrc3.c VRC3_count/VRC3_reload (uint16, saved as 1 byte)
    - mmc3.c m555_count (uint32, saved as 2 bytes), m555_count_-
      expired (uint8, saved as 2 bytes - OOB write into adjacent
      BSS).
* unrom512.c UNROM-512 mapper 30 .srm save format: host-endian
  uint32 flash write counters. Now stored as LE on disk regardless
  of host (Battle Kid 2, Twin Dragons, Lizard, Sole, etc.).
* ~70 multi-byte single-variable SFORMAT/AddExState entries across
  36 board files were saved as host-byte-order. After the
  FlipByteOrder fix, these are now byte-swapped on BE so cross-
  platform savestates round-trip correctly.
* coolgirl.c new ExStateLE() macro added; 22 multi-byte sites.
* pic16c5x.c 11 multi-byte AddExState calls (m_PC, m_PREVPC,
  m_CONFIG, m_WDT, m_prescaler, m_opcode, m_STACK[0/1], m_icount,
  m_delay_timer, m_rtcc, m_inst_cycles, m_clock2cycle).
* onebus.c PowerJoy Supermax submapper detection used non-portable
  *(uint32*)&info->MD5 cast that read different bytes on LE vs BE.
* fds.c clean up redundant FCEUSTATE_RLSB encoding in AddExState
  calls that also passed type=1 (idempotent OR; readability fix).

DOCUMENTATION
=============

* input.c UpdateGP's *(uint32*)data cast looks like a typical
  endian bug but is actually correct (the libretro frontend builds
  JSReturn with matching host-uint32 shifts). Comment added to
  prevent future "fixes" from breaking it.

Limitations not addressed
=========================

* Element-stride-aware byte swapping. The savestate byte-swap
  mechanism (FlipByteOrder over the entire SFORMAT entry buffer)
  is structurally wrong for arrays of multi-byte values: it
  reverses the whole buffer end-to-end instead of byte-swapping
  each element. Several places that need cross-platform-portable
  arrays (VRC7 sound state, jyasic chr[8]) work around this by
  either splitting arrays into per-element SFORMAT entries (n106
  PlayIndex, bandai reg) or by skipping save entirely on BE via
  #ifndef GEKKO. A proper fix would extend the size encoding with
  an element-stride field. Left for a future change because it
  would change the savestate format.

* Strict-aliasing UB in ppu.c (around 9 sites doing
  *(uint32*)uint8_buf for fast 4-byte writes via FCEU_dwmemset).
  Works in practice with all common compilers because the patterns
  are byte-symmetric, but is formally UB.

* FCEU_gmalloc calls exit(1) on OOM. A libretro core should never
  exit() because that takes down the whole frontend. Used by
  100+ call sites; refactoring to return-NULL is out of scope here.

Testing
=======

* Build: clean on `make platform=unix` with -O2; no new warnings.
* FlipByteOrder fix verified by hand-trace and a standalone unit
  test for counts 2, 4, 8.
* uppow2 fix verified by unit test across 13 boundary cases.
* SFORMAT size mismatches and missing-RLSB cases identified by
  Python static-analysis scripts that cross-reference SFORMAT
  entries against variable declarations.
* iNES 2.0 exponent fix verified by hand-tracing what byte 0xFF
  produces post-fix: exp=30 (capped), mult=7, size=3 GiB nominal,
  capped to 1 GiB, capped to 2 GiB by uppow2, FCEU_malloc returns
  NULL on most systems, loader returns 0. No heap overflow for
  any input byte.
* Savestate-loaded array index audit: built a Python scanner that
  extracts each AddExState/SFORMAT entry and cross-references the
  variable name against array-index uses in the same file. All
  flagged sites covered.
* A libFuzzer harness and seed corpus generator (fuzz_main.c,
  gen_seed_corpus.py) accompany this submission for ongoing
  regression testing.
2026-05-04 02:15:40 +02:00

230 lines
6.2 KiB
C

/* FCE Ultra - NES/Famicom Emulator
*
* Copyright notice for this file:
* Copyright (C) 2012 CaH4e3
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "mapinc.h"
#include "emu2413.h"
static int32 dwave = 0;
static OPLL *VRC7Sound = NULL;
static uint8 vrc7idx, preg[3], creg[8], mirr;
static uint8 IRQLatch, IRQa, IRQd;
static int32 IRQCount, CycleCount;
static uint8 *WRAM = NULL;
static uint32 WRAMSIZE;
static SFORMAT StateRegs[] =
{
{ &vrc7idx, 1, "VRCI" },
{ preg, 3, "PREG" },
{ creg, 8, "CREG" },
{ &mirr, 1, "MIRR" },
{ &IRQa, 1, "IRQA" },
{ &IRQd, 1, "IRQD" },
{ &IRQLatch, 1, "IRQL" },
{ &IRQCount, 4 | FCEUSTATE_RLSB, "IRQC" },
{ &CycleCount, 4 | FCEUSTATE_RLSB, "CYCC" },
{ 0 }
};
/* VRC7 Sound */
void DoVRC7Sound(void) {
int32 z, a;
if (FSettings.soundq >= 1)
return;
z = ((SOUNDTS << 16) / soundtsinc) >> 4;
a = z - dwave;
OPLL_fillbuf(VRC7Sound, &Wave[dwave], a, 1);
dwave += a;
}
void UpdateOPLNEO(int32 *Wave, int Count) {
OPLL_fillbuf(VRC7Sound, Wave, Count, 4);
}
void UpdateOPL(int Count) {
int32 z, a;
z = ((SOUNDTS << 16) / soundtsinc) >> 4;
a = z - dwave;
if (VRC7Sound && a)
OPLL_fillbuf(VRC7Sound, &Wave[dwave], a, 1);
dwave = 0;
}
static void VRC7SC(void) {
if (VRC7Sound)
OPLL_set_rate(VRC7Sound, FSettings.SndRate);
}
static void VRC7SKill(void) {
if (VRC7Sound)
OPLL_delete(VRC7Sound);
VRC7Sound = NULL;
}
static void VRC7_ESI(void) {
GameExpSound.RChange = VRC7SC;
GameExpSound.Kill = VRC7SKill;
VRC7Sound = OPLL_new(3579545, FSettings.SndRate ? FSettings.SndRate : 44100);
OPLL_reset(VRC7Sound);
OPLL_reset(VRC7Sound);
}
/* VRC7 Sound */
static void Sync(void) {
uint8 i;
setprg8r(0x10, 0x6000, 0);
setprg8(0x8000, preg[0]);
setprg8(0xA000, preg[1]);
setprg8(0xC000, preg[2]);
setprg8(0xE000, ~0);
for (i = 0; i < 8; i++)
setchr1(i << 10, creg[i]);
switch (mirr & 3) {
case 0: setmirror(MI_V); break;
case 1: setmirror(MI_H); break;
case 2: setmirror(MI_0); break;
case 3: setmirror(MI_1); break;
}
}
static DECLFW(VRC7SW) {
if (FSettings.SndRate) {
OPLL_writeReg(VRC7Sound, vrc7idx, V);
GameExpSound.Fill = UpdateOPL;
GameExpSound.NeoFill = UpdateOPLNEO;
}
}
static DECLFW(VRC7Write) {
A |= (A & 8) << 1; /* another two-in-oooone */
if (A >= 0xA000 && A <= 0xDFFF) {
A &= 0xF010;
creg[((A >> 4) & 1) | ((A - 0xA000) >> 11)] = V;
Sync();
} else if (A == 0x9030) {
VRC7SW(A, V);
} else switch (A & 0xF010) {
case 0x8000: preg[0] = V; Sync(); break;
case 0x8010: preg[1] = V; Sync(); break;
case 0x9000: preg[2] = V; Sync(); break;
case 0x9010: vrc7idx = V; break;
case 0xE000: mirr = V & 3; Sync(); break;
case 0xE010: IRQLatch = V; X6502_IRQEnd(FCEU_IQEXT); break;
case 0xF000:
IRQa = V & 2;
IRQd = V & 1;
if (V & 2)
IRQCount = IRQLatch;
CycleCount = 0;
X6502_IRQEnd(FCEU_IQEXT);
break;
case 0xF010:
IRQa = IRQd;
X6502_IRQEnd(FCEU_IQEXT);
break;
}
}
static void VRC7Power(void) {
Sync();
SetWriteHandler(0x6000, 0x7FFF, CartBW);
SetReadHandler(0x6000, 0xFFFF, CartBR);
SetWriteHandler(0x8000, 0xFFFF, VRC7Write);
FCEU_CheatAddRAM(WRAMSIZE >> 10, 0x6000, WRAM);
}
static void VRC7Close(void) {
if (WRAM)
FCEU_gfree(WRAM);
WRAM = NULL;
}
static void VRC7IRQHook(int a) {
if (IRQa) {
CycleCount += a * 3;
while (CycleCount >= 341) {
CycleCount -= 341;
IRQCount++;
if (IRQCount == 0x100) {
IRQCount = IRQLatch;
X6502_IRQBegin(FCEU_IQEXT);
}
}
}
}
static void StateRestore(int version) {
Sync();
#ifndef GEKKO
OPLL_forceRefresh(VRC7Sound);
#endif
}
void Mapper85_Init(CartInfo *info) {
info->Power = VRC7Power;
info->Close = VRC7Close;
MapIRQHook = VRC7IRQHook;
WRAMSIZE = 8192;
WRAM = (uint8*)FCEU_gmalloc(WRAMSIZE);
SetupCartPRGMapping(0x10, WRAM, WRAMSIZE, 1);
AddExState(WRAM, WRAMSIZE, 0, "WRAM");
if (info->battery) {
info->SaveGame[0] = WRAM;
info->SaveGameLen[0] = WRAMSIZE;
}
GameStateRestore = StateRestore;
VRC7_ESI();
AddExState(&StateRegs, ~0, 0, 0);
/* Ignoring these sound state files for Wii since it causes states unable to load */
#ifndef GEKKO
/* Sound states */
AddExState(&VRC7Sound->adr, sizeof(VRC7Sound->adr), 0, "ADDR");
AddExState(&VRC7Sound->out, sizeof(VRC7Sound->out), 0, "OUT0");
AddExState(&VRC7Sound->realstep, sizeof(VRC7Sound->realstep), 0, "RTIM");
AddExState(&VRC7Sound->oplltime, sizeof(VRC7Sound->oplltime), 0, "TIME");
AddExState(&VRC7Sound->opllstep, sizeof(VRC7Sound->opllstep), 0, "STEP");
AddExState(&VRC7Sound->prev, sizeof(VRC7Sound->prev), 0, "PREV");
AddExState(&VRC7Sound->next, sizeof(VRC7Sound->next), 0, "NEXT");
AddExState(&VRC7Sound->LowFreq, sizeof(VRC7Sound->LowFreq), 0, "LFQ0");
AddExState(&VRC7Sound->HiFreq, sizeof(VRC7Sound->HiFreq), 0, "HFQ0");
AddExState(&VRC7Sound->InstVol, sizeof(VRC7Sound->InstVol), 0, "VOLI");
AddExState(&VRC7Sound->CustInst, sizeof(VRC7Sound->CustInst), 0, "CUSI");
AddExState(&VRC7Sound->slot_on_flag, sizeof(VRC7Sound->slot_on_flag), 0, "FLAG");
AddExState(&VRC7Sound->pm_phase, sizeof(VRC7Sound->pm_phase), 0, "PMPH");
AddExState(&VRC7Sound->lfo_pm, sizeof(VRC7Sound->lfo_pm), 0, "PLFO");
AddExState(&VRC7Sound->am_phase, sizeof(VRC7Sound->am_phase), 0, "AMPH");
AddExState(&VRC7Sound->lfo_am, sizeof(VRC7Sound->lfo_am), 0, "ALFO");
AddExState(&VRC7Sound->patch_number, sizeof(VRC7Sound->patch_number), 0, "PNUM");
AddExState(&VRC7Sound->key_status, sizeof(VRC7Sound->key_status), 0, "KET");
AddExState(&VRC7Sound->mask, sizeof(VRC7Sound->mask), 0, "MASK");
AddExState((uint8 *)VRC7Sound->slot, sizeof(VRC7Sound->slot), 0, "SLOT");
#endif
}
void NSFVRC7_Init(void) {
SetWriteHandler(0x9010, 0x901F, VRC7Write);
SetWriteHandler(0x9030, 0x903F, VRC7Write);
VRC7_ESI();
}