In the test, I have an internal `__call` function for `_ZendTestMagicCallForward` that calls the global function with name `$name` via `call_user_function`.
Note that observer writes the pointer to the previously observed frame in the last temporary of the new call frame (`*prev_observed_frame`).
The following happens:
First, we call `$test->callee`, this will be handled via a trampoline with T=2 for the two arguments. The call frame is allocated at this point. This call frame is not observed because it has `ZEND_ACC_CALL_VIA_TRAMPOLINE` set. Next we use `ZEND_CALL_TRAMPOLINE` to call the trampoline, this reuses the stack frame allocated earlier with T=2, but this time it is observed. The pointer to the previous frame is written outside of the call frame because `T` is too small (should be 3). We are now in the internal function `_ZendTestMagicCallForward::__call` where we call the global function `callee`. This will push a new call frame which will overlap `*prev_observed_frame`. This value gets overwritten by `zend_init_func_execute_data` when `EX(opline)` is set because `*prev_observed_frame` overlaps with `EX(opline)`. From now on, `*prev_observed_frame` is corrupted. When `zend_observer_fcall_end` is called this will result in reading wrong value `*prev_observed_frame` into `current_observed_frame`. This causes issues in `zend_observer_fcall_end_all` leading to the segfault we observe.
Despite function with `ZEND_ACC_CALL_VIA_TRAMPOLINE` not being observed, the reuse of call frames makes problems when `T` is not large enough.
To fix this, we make sure to add 1 to `T` if `ZEND_OBSERVER_ENABLED` is true.
Closes GH-16252.
The create_obj handler of InternalIterator is overwritten, but not the
clone_obj handler. This is not allowed.
In PHP 8.2 this didn't cause a segfault because the standard object
handler was used for the clone instead of the internal handler.
So then it allocates and frees the object using the standard object handlers.
In 8.3 however, the object is created using the standard object handler and
freed using the custom handler, resulting in the buffer overflow.
Even though bisect points to 1e1ea4f this only reveals the bug.
Closes GH-14882.
is_zend_ptr() expected zend_mm_heap.huge_list to be circular, but it's in fact NULL-terminated. It could crash when at least one huge block exists and the ptr did not belong to any block.
Although the issue was demonstrated using Curl, the issue is purely in
the streams layer of PHP.
Full analysis is written in GH-11078 [1], but here is the brief version:
Here's what actually happens:
1) We're creating a FILE handle from a stream using the casting mechanism.
This will create a cookie-based FILE handle using funopen.
2) We're reading stream data using fread from the userspace stream. This will
temporarily set a buffer into a field _bf.base [2]. This buffer is now equal
to the upload buffer that Curl allocated and note that that buffer is owned
by Curl.
3) The fatal error occurs and we bail out from the fread function, notice how
the reset code is never executed and so the buffer will still point to
Curl's upload buffer instead of FILE's own buffer [3].
4) The resources are destroyed, this includes our opened stream and because the
FILE handle is cached, it gets destroyed as well.
In fact, the stream code calls through fclose on purpose in this case.
5) The fclose code frees the _bs.base buffer [4].
However, this is not the buffer that FILE owns but the one that Curl owns
because it isn't reset properly due to the bailout!
6) The objects are getting destroyed, and so the curl free logic is invoked.
When Curl tries to gracefully clean up, it tries to free the buffer.
But that buffer is actually already freed mistakingly by the C library!
This also explains why we can't reproduce it on Linux: this bizarre buffer
swapping only happens on macOS and BSD, not on Linux.
To solve this, we switch to an unbuffered mode for cookie-based FILEs.
This avoids any stateful problems related to buffers especially when the
bailout mechanism triggers. As streams have their own buffering
mechanism, I don't expect this to impact performance.
[1] https://github.com/php/php-src/issues/11078#issuecomment-2155616843
[2] 5e566be7a7/stdio/FreeBSD/fread.c (L102-L103)
[3] 5e566be7a7/stdio/FreeBSD/fread.c (L117)
[4] 5e566be7a7/stdio/FreeBSD/fclose.c (L66-L67)
Closes GH-14524.
Some modules may reset _fmode, which causes mangling of line endings.
Always be explicit like we do in other places where the native open call
is used.
Closes GH-14218.
Fixes GH-13970
Closes GH-14105
We cannot validate at compile-time for multiple reasons:
* Evaluating the argument naively with zend_get_attribute_value can lead to code
execution at compile time through the new expression, leading to possible
reentrance of the compiler.
* Even if the evaluation was possible, it would need to be restricted to the
current file, because constant values coming from other files can change
without affecting the current compilation unit. For this reason, validation
would need to be repeated at runtime anyway.
* Enums cannot be instantiated at compile-time (the actual bug report). This
could be allowed here, because the value is immediately destroyed. But given
the other issues, this won't be needed.
Instead, we just move it to runtime entirely. It's only needed for
ReflectionAttribute::newInstance(), which is not particularly a hot path. The
checks are also simple.
This also fixes skipped tests due to different naming "zend-test"
instead of "zend_test" and "PDO" instead of "pdo":
- ext/dom/tests/libxml_global_state_entity_loader_bypass.phpt
- ext/simplexml/tests/libxml_global_state_entity_loader_bypass.phpt
- ext/xmlreader/tests/libxml_global_state_entity_loader_bypass.phpt
- ext/zend_test/tests/observer_sqlite_create_function.phpt
EXTENSIONS section is used for the Windows build to load the non-static
extensions.
Closes GH-13276
* fix segfault in `ZEND_BIND_STATIC`
In case a `ZEND_BIND_STATIC` is being executed, while the current chunk is full,
the `zend_array_dup()` call will trigger a OOM in ZendMM which will crash, as
the opline might be a dangling pointer.
* add missing test
* `assert()`ing seems easier than trying to make the compiler to not optimize
* moved from function call to INI setting, so we can use this in other places as well
* make `assert()` work no NDEBUG builds
* document magic number
* fix segfault in `ZEND_FUNC_GET_ARGS`
In case a `ZEND_FUNC_GET_ARGS` is being executed, while the current chunk is
full, the `zend_new_array()` call will trigger a OOM in ZendMM which will crash,
as the opline might be a dangling pointer.
---------
Co-authored-by: Florian Engelhardt <florian@engelhardt.tc>
