CVE-2022-49913

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix inode list leak during backref walking at find_parent_nodes()

During backref walking, at find_parent_nodes(), if we are dealing with a data extent and we get an error while resolving the indirect backrefs, at resolve_indirect_refs(), or in the while loop that iterates over the refs in the direct refs rbtree, we end up leaking the inode lists attached to the direct refs we have in the direct refs rbtree that were not yet added to the refs ulist passed as argument to find_parent_nodes(). Since they were not yet added to the refs ulist and prelim_release() does not free the lists, on error the caller can only free the lists attached to the refs that were added to the refs ulist, all the remaining refs get their inode lists never freed, therefore leaking their memory.

Fix this by having prelim_release() always free any attached inode list to each ref found in the rbtree, and have find_parent_nodes() set the refs inode list to NULL once it transfers ownership of the inode list to a ref added to the refs ulist passed to find_parent_nodes().

Weakness

The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.

Affected Software

Potential Mitigations

• Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone.
• For example, glibc in Linux provides protection against free of invalid pointers.
• When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [REF-391].
• To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and std::unique_ptr (specified by an upcoming revision of the C++ standard, informally referred to as C++ 1x), or equivalent solutions such as Boost.

References

• https://git.kernel.org/stable/c/222a3d533027b9492d5b7f5ecdc01a90f57bb5a9
• https://git.kernel.org/stable/c/61e06128113711df0534c404fb6bb528eb7d2332
• https://git.kernel.org/stable/c/6a6731a0df8c47ecc703bd7bb73459df767051e0
• https://git.kernel.org/stable/c/83ea8c5b54d452a5769e605e3c5c687e8ca06d89
• https://git.kernel.org/stable/c/92876eec382a0f19f33d09d2c939e9ca49038ae5