In the Linux kernel, the following vulnerability has been resolved:
bpf: Tighten cgroup storage cookie checks for prog arrays
The fix in commit abad3d0bad72 (bpf: Fix oob access in cgroup local storage) is still incomplete. The prog-array compatibility check treats a program with no cgroup storage as compatible with any stored storage cookie. This allows a storage-less program to bridge a tail call chain between an entry program and a storage-using callee even though cgroup local storage at runtime still follows the callers context, that is, A -> B(no storage) -> C(storage) path.
Requiring exact cookie equality would break the legitimate case of a storage-less leaf program being tail called from a storage-using one. Instead, only accept a zero storage cookie if the program cannot perform tail calls itself. This keeps A -> B(no storage) working while rejecting the A -> B(no storage) -> C(storage) bridge.
References
- https://git.kernel.org/stable/c/10627ddc0167aab5c1c390a10ef461e9937aba08
- https://git.kernel.org/stable/c/1c762d28698483ce7c372091f34d86e4d4828652
- https://git.kernel.org/stable/c/46fbafe3d2d569d828e8d24a7dbe1659f63685cf
- https://git.kernel.org/stable/c/87177497cca90bf4fcfb759eb898560eb5b46a10
- https://git.kernel.org/stable/c/9ca06849c4239aa2d580c54651f8588c51cb398b
- https://git.kernel.org/stable/c/cb22dc79528eb26a46d346c3118dbd6b14c70609
- https://git.kernel.org/stable/c/eb73056ce2a6f101ddd3bdba89af6b24ebffff85