1c78ed95d4
There is a race between releasing and re-acquiring an interned
GRefString if this happens on two threads at the same time. This can
result in already freed memory to be returned from
g_ref_string_new_intern().
| Thread 1 | Thread 2 |
| ------------------------------ | ----------------------------- |
| g_ref_string_release() | g_ref_string_new_intern() |
| g_atomic_rc_box_release_full() | g_mutex_lock() |
| | g_hash_table_lookup() |
| remove_if_interned() | g_ref_string_acquire() |
| g_mutex_lock() | g_mutex_unlock() |
| g_hash_table_remove() | |
| g_mutex_unlock() | |
| g_free() | |
| | return res; // this is freed |
This use-after-free usually also gives a critical warning because
g_atomic_ref_count_inc() checks for the refcount having been 0
before incrementing.
It is not possible to safely implement weak references via garcbox.
To avoid this race do not implement weak references via garcbox but
instead implement the allocation of the string manually with a manually
managed reference count. This allows to safely resurrect the interned
string if the above race happens, and also avoids other races.
As a side-effect this also
* reduces the allocation size in addition to the actual string length
from 32 bytes to 16 bytes on 64 bit platforms and keeps it at 16 bytes
on 32 bit platforms,
* doesn't lock a mutex when freeing non-interned GRefStrings.
GLib
GLib is the low-level core library that forms the basis for projects such as GTK and GNOME. It provides data structure handling for C, portability wrappers, and interfaces for such runtime functionality as an event loop, threads, dynamic loading, and an object system.
The official download locations are: https://download.gnome.org/sources/glib
The official web site is: https://www.gtk.org/
Installation
See the file ‘INSTALL.md’. There is separate and more in-depth documentation for building GLib on Windows.
Supported versions
Upstream GLib only supports the most recent stable release series, the previous stable release series, and the current development release series. All older versions are not supported upstream and may contain bugs, some of which may be exploitable security vulnerabilities.
See SECURITY.md for more details.
Documentation
API documentation is available online for GLib for the:
Discussion
If you have a question about how to use GLib, seek help on GNOME’s Discourse
instance. Alternatively, ask a question
on StackOverflow and tag it glib.
Reporting bugs
Bugs should be reported to the GNOME issue tracking system. You will need to create an account for yourself. You may also submit bugs by e-mail (without an account) by e-mailing incoming+gnome-glib-658-issue-@gitlab.gnome.org, but this will give you a degraded experience.
Bugs are for reporting problems in GLib itself, not for asking questions about how to use it. To ask questions, use one of our discussion forums.
In bug reports please include:
- Information about your system. For instance:
- What operating system and version
- For Linux, what version of the C library
- And anything else you think is relevant.
- How to reproduce the bug.
- If you can reproduce it with one of the test programs that are built
in the
tests/subdirectory, that will be most convenient. Otherwise, please include a short test program that exhibits the behavior. As a last resort, you can also provide a pointer to a larger piece of software that can be downloaded.
- If you can reproduce it with one of the test programs that are built
in the
- If the bug was a crash, the exact text that was printed out when the crash occurred.
- Further information such as stack traces may be useful, but is not necessary.
Contributing to GLib
Please follow the contribution guide to know how to start contributing to GLib.
Patches should be submitted as merge requests to gitlab.gnome.org. Note that you will need to be logged in to the site to use this page. If the patch fixes an existing issue, please refer to the issue in your commit message with the following notation (for issue 123):
Closes: #123
Otherwise, create a new merge request that introduces the change. Filing a separate issue is not required.