CVE-2021-46973

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

net: qrtr: Avoid potential use after free in MHI send

It is possible that the MHI ul_callback will be invoked immediately following the queueing of the skb for transmission, leading to the callback decrementing the refcount of the associated sk and freeing the skb.

As such the dereference of skb and the increment of the sk refcount must happen before the skb is queued, to avoid the skb to be used after free and potentially the sk to drop its last refcount..

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 Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.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/03c649dee8b1eb5600212a249542a70f47a5ab40
• https://git.kernel.org/stable/c/47a017f33943278570c072bc71681809b2567b3a
• https://git.kernel.org/stable/c/48ec949ac979b4b42d740f67b6177797af834f80
• https://git.kernel.org/stable/c/ea474054c2cc6e1284604b21361f475c7cc8c0a0
• https://git.kernel.org/stable/c/03c649dee8b1eb5600212a249542a70f47a5ab40
• https://git.kernel.org/stable/c/47a017f33943278570c072bc71681809b2567b3a
• https://git.kernel.org/stable/c/48ec949ac979b4b42d740f67b6177797af834f80
• https://git.kernel.org/stable/c/ea474054c2cc6e1284604b21361f475c7cc8c0a0