https://bugs.winehq.org/show_bug.cgi?id=56650
Bug ID: 56650 Summary: Report on SELinux 'execheap' Issues with wine-preloader Product: Wine Version: 9.8 Hardware: x86-64 OS: Linux Status: UNCONFIRMED Severity: normal Priority: P2 Component: -unknown Assignee: wine-bugs@winehq.org Reporter: chplee@gmail.com Distribution: ---
This report was prepared by ChatGPT. I'm sorry that my own ability is not enough to support such a large amount of code analysis, so I have to turn to ChatGPT.
I'm filing this report because a lot of people are suffering from this problem.
Please refer to: https://bugzilla.redhat.com/show_bug.cgi?id=2247299
### Report on SELinux 'execheap' Issues with `wine-preloader`
#### Introduction The `wine-preloader` program is a crucial part of the Wine software, which allows Windows applications to run on Unix-like operating systems. An issue has been identified where SELinux prevents `wine-preloader` from executing code in writable memory regions, raising security alerts related to 'execheap' accesses. This report identifies potential sources of the issue in the program and provides recommendations for modifications.
#### Potential Issues Identified 1. **Memory Mapping and Protection Setup**: In `wine-preloader`, memory mapping is handled with protections set that could potentially include both write and execute permissions. This is particularly evident in the function calls to `wld_mmap`, where memory protection flags are set based on the segment flags parsed from ELF headers.
```c wld_mmap((void *)(l->l_addr + c->mapstart), c->mapend - c->mapstart, c->prot, MAP_FIXED | MAP_COPY | MAP_FILE, fd, c->mapoff); ```
Here, the `c->prot` can contain combinations of `PROT_READ`, `PROT_WRITE`, and `PROT_EXEC` based on the segment's flags.
2. **Dynamic Code Generation**: Dynamic generation or modification of code could potentially occur, though not explicitly shown in the code snippets provided, it could be inferred from the overall functionality where executable code may be modified or generated on-the-fly.
3. **Modifying Memory Protection Attributes**: The use of `wld_mprotect` to change the protection attributes of memory pages could lead to states where pages are both writable and executable.
```c wld_mprotect((caddr_t) (zero & ~page_mask), page_size, c->prot|PROT_WRITE); ```
Although this snippet aims to make pages writable temporarily, if combined inappropriately with executable flags elsewhere, it could trigger SELinux policies.
#### Recommendations - **Restricting Memory Permissions**: Enforce strict separations between writable and executable pages. Modify the logic that sets memory protections to ensure that no memory page is both writable and executable at the same time. This can be achieved by adjusting the ELF segment loading routines to separate code and data segments clearly.
- **Use of Memory Protection Changes**: Implement a clear two-step process for handling memory that needs to be executable: - Initially, set memory to writable to modify or generate code. - Once modifications are complete, change the memory protection to executable only (removing write permissions).
- **Code Audit and Testing**: Conduct a thorough audit of the places where memory permissions are set. Test under a SELinux-enforced environment to ensure that the adjustments meet security policies without hindering functionality.
- **SELinux Policy Adjustments**: If `wine-preloader` inherently requires certain operations that SELinux policies restrict, consider creating custom SELinux policy modules that allow specific actions while maintaining overall security. This should be done cautiously to avoid creating unnecessary security holes.
#### Conclusion Adjustments to `wine-preloader` should focus on ensuring that memory regions are either writable or executable but never both. By adhering to security best practices and possibly adjusting SELinux policies, `wine-preloader` can function effectively without triggering security violations in SELinux environments.