Fix GH-22060: UAF in class-autoloader dispatch on self-unregister#22085
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iliaal wants to merge 1 commit into
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Fix GH-22060: UAF in class-autoloader dispatch on self-unregister#22085iliaal wants to merge 1 commit into
iliaal wants to merge 1 commit into
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zend_perform_class_autoload walked the autoloader hashtable and called zend_call_known_fcc on each FCC without pinning its refcounted owners. When the autoloader's PHP body called spl_autoload_unregister([$this, 'load']), the hash bucket destructor released the last ref on $this and freed it mid-call; the subsequent $this->data read landed in freed memory. Pin object and closure manually around the call. Don't use zend_fcc_dup/zend_fcc_dtor: zend_fcc_dtor frees trampoline storage based on ZEND_ACC_CALL_VIA_TRAMPOLINE, which would double-free the hash entry's trampoline copy for __call-based autoloaders. Fixes phpGH-22060
Girgias
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May 24, 2026
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Girgias
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So this is the exact problem that #22126 has.
I would appreciate that rather just asking an LLM to do fixes at calls sites randomly to instead use the human capability of critical thinking to actually reason and understand the underlying issue, and determining that the root cause of the problem is within the API.
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A method-bound autoloader registered as
[$obj, 'load']can callspl_autoload_unregister([$this, 'load'])from inside its own callback. The hash entry's destructor releases the last ref on the object, frees it, and the rest of the PHP body (e.g.echo $this->data) reads freed memory. The dispatch loop inzend_perform_class_autoloadcallszend_call_known_fcc(func_info, ...), butzend_call_functionreadsfci_cache->objectintoEX(This)without bumping the refcount; the call convention is that the caller holds the ref, and here the only ref was the hash entry's.Fix pins
objectandclosureacross the call withGC_ADDREF/OBJ_RELEASE. The pointers are saved locally before the call so the releases work even whenfunc_infoitself is freed mid-call by self-unregister.