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Fix GH-14361: Deep recursion in zend_cfg.c causes segfault instead of error #14432

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Fix GH-14361: Deep recursion in zend_cfg.c causes segfault instead of error #14432

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62ebccc
Indent current code
nielsdos Jun 3, 2024
d2b79af
Change CFG reachability algorithm to an iterative algorithm
nielsdos Jun 3, 2024
1943c2d
Remove tail call optimization
nielsdos Jun 4, 2024
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130 changes: 72 additions & 58 deletions Zend/Optimizer/zend_cfg.c
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Original file line number Diff line number Diff line change
Expand Up @@ -28,80 +28,94 @@ static void zend_mark_reachable(zend_op *opcodes, zend_cfg *cfg, zend_basic_bloc
{
zend_basic_block *blocks = cfg->blocks;

while (1) {
int i;
zend_worklist work;
ALLOCA_FLAG(list_use_heap)
ZEND_WORKLIST_ALLOCA(&work, cfg->blocks_count, list_use_heap);

b->flags |= ZEND_BB_REACHABLE;
if (b->successors_count == 0) {
b->flags |= ZEND_BB_EXIT;
return;
}
zend_worklist_push(&work, b - cfg->blocks);

for (i = 0; i < b->successors_count; i++) {
zend_basic_block *succ = blocks + b->successors[i];
while (zend_worklist_len(&work)) {
b = cfg->blocks + zend_worklist_pop(&work);

if (b->len != 0) {
uint8_t opcode = opcodes[b->start + b->len - 1].opcode;
if (opcode == ZEND_MATCH) {
succ->flags |= ZEND_BB_TARGET;
} else if (opcode == ZEND_SWITCH_LONG || opcode == ZEND_SWITCH_STRING) {
if (i == b->successors_count - 1) {
succ->flags |= ZEND_BB_FOLLOW | ZEND_BB_TARGET;
} else {
succ->flags |= ZEND_BB_TARGET;
}
} else if (b->successors_count == 1) {
if (opcode == ZEND_JMP) {
bool finished = false;
while (!finished) {
int i;

b->flags |= ZEND_BB_REACHABLE;
if (b->successors_count == 0) {
b->flags |= ZEND_BB_EXIT;
break;
}

for (i = 0; i < b->successors_count; i++) {
zend_basic_block* succ = blocks + b->successors[i];

if (b->len != 0) {
uint8_t opcode = opcodes[b->start + b->len - 1].opcode;
if (opcode == ZEND_MATCH) {
succ->flags |= ZEND_BB_TARGET;
} else {
succ->flags |= ZEND_BB_FOLLOW;

if ((cfg->flags & ZEND_CFG_STACKLESS)) {
if (opcode == ZEND_INCLUDE_OR_EVAL ||
opcode == ZEND_GENERATOR_CREATE ||
opcode == ZEND_YIELD ||
opcode == ZEND_YIELD_FROM ||
opcode == ZEND_DO_FCALL ||
opcode == ZEND_DO_UCALL ||
opcode == ZEND_DO_FCALL_BY_NAME) {
succ->flags |= ZEND_BB_ENTRY;
}
} else if (opcode == ZEND_SWITCH_LONG || opcode == ZEND_SWITCH_STRING) {
if (i == b->successors_count - 1) {
succ->flags |= ZEND_BB_FOLLOW | ZEND_BB_TARGET;
} else {
succ->flags |= ZEND_BB_TARGET;
}
if ((cfg->flags & ZEND_CFG_RECV_ENTRY)) {
if (opcode == ZEND_RECV ||
opcode == ZEND_RECV_INIT) {
succ->flags |= ZEND_BB_RECV_ENTRY;
} else if (b->successors_count == 1) {
if (opcode == ZEND_JMP) {
succ->flags |= ZEND_BB_TARGET;
} else {
succ->flags |= ZEND_BB_FOLLOW;

if ((cfg->flags & ZEND_CFG_STACKLESS)) {
if (opcode == ZEND_INCLUDE_OR_EVAL ||
opcode == ZEND_GENERATOR_CREATE ||
opcode == ZEND_YIELD ||
opcode == ZEND_YIELD_FROM ||
opcode == ZEND_DO_FCALL ||
opcode == ZEND_DO_UCALL ||
opcode == ZEND_DO_FCALL_BY_NAME) {
succ->flags |= ZEND_BB_ENTRY;
}
}
if ((cfg->flags & ZEND_CFG_RECV_ENTRY)) {
if (opcode == ZEND_RECV ||
opcode == ZEND_RECV_INIT) {
succ->flags |= ZEND_BB_RECV_ENTRY;
}
}
}
}
} else {
ZEND_ASSERT(b->successors_count == 2);
if (i == 0) {
succ->flags |= ZEND_BB_TARGET;
} else {
succ->flags |= ZEND_BB_FOLLOW;
ZEND_ASSERT(b->successors_count == 2);
if (i == 0) {
succ->flags |= ZEND_BB_TARGET;
} else {
succ->flags |= ZEND_BB_FOLLOW;
}
}
} else {
succ->flags |= ZEND_BB_FOLLOW;
}
} else {
succ->flags |= ZEND_BB_FOLLOW;
}

if (i == b->successors_count - 1) {
/* Tail call optimization */
if (succ->flags & ZEND_BB_REACHABLE) {
return;
}
if (i == b->successors_count - 1) {
/* Tail call optimization */
if (succ->flags & ZEND_BB_REACHABLE) {
finished = true;
break;
}

b = succ;
break;
} else {
/* Recursively check reachability */
if (!(succ->flags & ZEND_BB_REACHABLE)) {
zend_mark_reachable(opcodes, cfg, succ);
b = succ;
break;
} else {
/* Recursively check reachability */
if (!(succ->flags & ZEND_BB_REACHABLE)) {
zend_worklist_push(&work, succ - cfg->blocks);
}
}
}
}
}

ZEND_WORKLIST_FREE_ALLOCA(&work, list_use_heap);
}
/* }}} */

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