Fix GH-17577: JIT packed type guard crash #17584
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nielsdos
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When a guard check is created for a variable to check if it's a packed array, it is possible that there was no prior type check for that variable. This happens in the global scope for example when the variable aliases. In the test, this causes a dereference of address 8 because the integer element in `$a` is interpreted as an array address. This patch adds a check to see if the guard is handled. If we were not able to determine or guard the type then we also cannot know the array is packed.
dstogov
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Jan 27, 2025
|
The particular code responsible for setting diff --git a/ext/opcache/jit/zend_jit_trace.c b/ext/opcache/jit/zend_jit_trace.c
index c138a5bcb0a..8fd0d1323d0 100644
--- a/ext/opcache/jit/zend_jit_trace.c
+++ b/ext/opcache/jit/zend_jit_trace.c
@@ -1935,7 +1935,8 @@ static zend_ssa *zend_jit_trace_build_tssa(zend_jit_trace_rec *trace_buffer, uin
zend_ssa_var_info *info = &tssa->var_info[tssa->ops[idx].op1_use];
- if (MAY_BE_PACKED(info->type) && MAY_BE_HASH(info->type)) {
+ if (MAY_BE_PACKED(info->type) && MAY_BE_HASH(info->type)
+ && (info->type & (MAY_BE_ANY|MAY_BE_UNDEF)) == MAY_BE_ARRAY) {
info->type |= MAY_BE_PACKED_GUARD;
if (orig_op1_type & IS_TRACE_PACKED) {
info->type &= ~(MAY_BE_ARRAY_NUMERIC_HASH|MAY_BE_ARRAY_STRING_HASH);
@@ -4162,7 +4163,6 @@ static const void *zend_jit_trace(zend_jit_trace_rec *trace_buffer, uint32_t par
}
if ((info & MAY_BE_PACKED_GUARD) != 0
- && (info & MAY_BE_GUARD) == 0
&& (trace_buffer->stop == ZEND_JIT_TRACE_STOP_LOOP
|| trace_buffer->stop == ZEND_JIT_TRACE_STOP_RECURSIVE_CALL
|| trace_buffer->stop == ZEND_JIT_TRACE_STOP_RECURSIVE_RET)
If I do this, and keep the assertion for the stack type to be |
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When a guard check is created for a variable to check if it's a packed array, it is possible that there was no prior type check for that variable. This happens in the global scope for example when the variable aliases. In the test, this causes a dereference of address 8 because the integer element in
$ais interpreted as an array address and zend_array.u.flags is at offset 8.This patch adds a check to see if the guard is handled.
If we were not able to determine or guard the type is array, then we also cannot know the array is packed.
An alternative I thought about was emitting a type check in this branch, but that can cause incorrect guard motion in case of aliasing. In such case we also shouldn't clear the
MAY_BE_PACKED_GUARDlike it does now.