CVE-2021-46969

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

bus: mhi: core: Fix invalid error returning in mhi_queue

mhi_queue returns an error when the doorbell is not accessible in the current state. This can happen when the device is in non M0 state, like M3, and needs to be waken-up prior ringing the DB. This case is managed earlier by triggering an asynchronous M3 exit via controller resume/suspend callbacks, that in turn will cause M0 transition and DB update.

So, since its not an error but just delaying of doorbell update, there is no reason to return an error.

This also fixes a use after free error for skb case, indeed a caller queuing skb will try to free the skb if the queueing fails, but in that case queueing has been done.

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 Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.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/0ecc1c70dcd32c0f081b173a1a5d89952686f271
• https://git.kernel.org/stable/c/a99b661c3187365f81026d89b1133a76cd2652b3
• https://git.kernel.org/stable/c/0ecc1c70dcd32c0f081b173a1a5d89952686f271
• https://git.kernel.org/stable/c/a99b661c3187365f81026d89b1133a76cd2652b3