CVE-2022-49085

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

drbd: Fix five use after free bugs in get_initial_state

In get_initial_state, it calls notify_initial_state_done(skb,..) if cb->args[5]==1. If genlmsg_put() failed in notify_initial_state_done(), the skb will be freed by nlmsg_free(skb). Then get_initial_state will goto out and the freed skb will be used by return value skb->len, which is a uaf bug.

Whats worse, the same problem goes even further: skb can also be freed in the notify_state_change -> notify_state calls below. Thus 4 additional uaf bugs happened.

My patch lets the problem callee functions: notify_initial_state_done and notify_*_state_change return an error code if errors happen. So that the error codes could be propagated and the uaf bugs can be avoid.

v2 reports a compilation warning. This v3 fixed this warning and built successfully in my local environment with no additional warnings. v2: https://lore.kernel.org/patchwork/patch/1435218/

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/0489700bfeb1e53eb2039c2291c67e71b0b40103
• https://git.kernel.org/stable/c/188fe6b26765edbad4055611c0f788b6870f4024
• https://git.kernel.org/stable/c/226e993c39405292781bfcf4b039a8db56aab362
• https://git.kernel.org/stable/c/594205b4936771a250f9d141e7e0fff21c3dd2d9
• https://git.kernel.org/stable/c/a972c768723359ec995579902473028fe3cd64b1
• https://git.kernel.org/stable/c/aadb22ba2f656581b2f733deb3a467c48cc618f6
• https://git.kernel.org/stable/c/b6a4055036eed1f5e239ce3d8b0db1ce38bba447
• https://git.kernel.org/stable/c/dcf6be17b5c53b741898d2223b23e66d682de300
• https://git.kernel.org/stable/c/de63e74da2333b4068bb79983e632db730fea97e