CVE-2026-23147

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

btrfs: zlib: fix the folio leak on S390 hardware acceleration

[BUG] After commit aa60fe12b4f4 (btrfs: zlib: refactor S390x HW acceleration buffer preparation), we no longer release the folio of the page cache of folio returned by btrfs_compress_filemap_get_folio() for S390 hardware acceleration path.

[CAUSE] Before that commit, we call kumap_local() and folio_put() after handling each folio.

Although the timing is not ideal (it release previous folio at the beginning of the loop, and rely on some extra cleanup out of the loop), it at least handles the folio release correctly.

Meanwhile the refactored code is easier to read, it lacks the call to release the filemap folio.

[FIX] Add the missing folio_put() for copy_data_into_buffer().

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/0d0f1314e8f86f5205f71f9e31e272a1d008e40b
• https://git.kernel.org/stable/c/e80617a5e1c246da2f112a1a072cdd535046adfe