CVE-2025-38544

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

rxrpc: Fix bug due to prealloc collision

When userspace is using AF_RXRPC to provide a server, it has to preallocate incoming calls and assign to them call IDs that will be used to thread related recvmsg() and sendmsg() together. The preallocated call IDs will automatically be attached to calls as they come in until the pool is empty.

To the kernel, the call IDs are just arbitrary numbers, but userspace can use the call ID to hold a pointer to prepared structs. In any case, the user isnt permitted to create two calls with the same call ID (call IDs become available again when the call ends) and EBADSLT should result from sendmsg() if an attempt is made to preallocate a call with an in-use call ID.

However, the cleanup in the error handling will trigger both assertions in rxrpc_cleanup_call() because the call isnt marked complete and isnt marked as having been released.

Fix this by setting the call state in rxrpc_service_prealloc_one() and then marking it as being released before calling the cleanup function.

Weakness

The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.

Affected Software

Extended Description

While assertion is good for catching logic errors and reducing the chances of reaching more serious vulnerability conditions, it can still lead to a denial of service. For example, if a server handles multiple simultaneous connections, and an assert() occurs in one single connection that causes all other connections to be dropped, this is a reachable assertion that leads to a denial of service.

Potential Mitigations

References

• https://git.kernel.org/stable/c/432c5363cd6fe5a928bbc94524d28b05515684dd
• https://git.kernel.org/stable/c/5385ad53793de2ab11e396bdcdaa65bb04b4dad6
• https://git.kernel.org/stable/c/69e4186773c6445b258fb45b6e1df18df831ec45
• https://git.kernel.org/stable/c/d8ffb47a443919277cb093c3db1ec6c0a06880b1