CVE-2022-48809

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

net: fix a memleak when uncloning an skb dst and its metadata

When uncloning an skb dst and its associated metadata, a new dst+metadata is allocated and later replaces the old one in the skb. This is helpful to have a non-shared dst+metadata attached to a specific skb.

The issue is the uncloned dst+metadata is initialized with a refcount of 1, which is increased to 2 before attaching it to the skb. When tun_dst_unclone returns, the dst+metadata is only referenced from a single place (the skb) while its refcount is 2. Its refcount will never drop to 0 (when the skb is consumed), leading to a memory leak.

Fix this by removing the call to dst_hold in tun_dst_unclone, as the dst+metadata refcount is already 1.

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/00e6d6c3bc14dfe32824e2c515f0e0f2d6ecf2f1
• https://git.kernel.org/stable/c/0be943916d781df2b652793bb2d3ae4f9624c10a
• https://git.kernel.org/stable/c/4ac84498fbe84a00e7aef185e2bb3e40ce71eca4
• https://git.kernel.org/stable/c/8b1087b998e273f07be13dcb5f3ca4c309c7f108
• https://git.kernel.org/stable/c/9eeabdf17fa0ab75381045c867c370f4cc75a613
• https://git.kernel.org/stable/c/a80817adc2a4c1ba26a7aa5f3ed886e4a18dff88
• https://git.kernel.org/stable/c/c1ff27d100e2670b03cbfddb9117e5f9fc672540
• https://git.kernel.org/stable/c/fdcb263fa5cda15b8cb24a641fa2718c47605314
• https://git.kernel.org/stable/c/00e6d6c3bc14dfe32824e2c515f0e0f2d6ecf2f1
• https://git.kernel.org/stable/c/0be943916d781df2b652793bb2d3ae4f9624c10a
• https://git.kernel.org/stable/c/4ac84498fbe84a00e7aef185e2bb3e40ce71eca4
• https://git.kernel.org/stable/c/8b1087b998e273f07be13dcb5f3ca4c309c7f108
• https://git.kernel.org/stable/c/9eeabdf17fa0ab75381045c867c370f4cc75a613
• https://git.kernel.org/stable/c/a80817adc2a4c1ba26a7aa5f3ed886e4a18dff88
• https://git.kernel.org/stable/c/c1ff27d100e2670b03cbfddb9117e5f9fc672540
• https://git.kernel.org/stable/c/fdcb263fa5cda15b8cb24a641fa2718c47605314