CVE-2023-53669

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

tcp: fix skb_copy_ubufs() vs BIG TCP

David Ahern reported crashes in skb_copy_ubufs() caused by TCP tx zerocopy using hugepages, and skb length bigger than ~68 KB.

skb_copy_ubufs() assumed it could copy all payload using up to MAX_SKB_FRAGS order-0 pages.

This assumption broke when BIG TCP was able to put up to 512 KB per skb.

We did not hit this bug at Google because we use CONFIG_MAX_SKB_FRAGS=45 and limit gso_max_size to 180000.

A solution is to use higher order pages if needed.

v2: add missing __GFP_COMP, or we leak memory.

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/3c77a377877acbaf03cd7caa21d3644a5dd16301
• https://git.kernel.org/stable/c/7e692df3933628d974acb9f5b334d2b3e885e2a6
• https://git.kernel.org/stable/c/7fa93e39fbb0566019c388a8038a4d58552e0910
• https://git.kernel.org/stable/c/9cd62f0ba465cf647c7d8c2ca7b0d99ea0c1328f