srpt RwCtxs UAF

Vulnerability analysis

When the SRP target driver allocates RDMA transfer contexts for a multi-buffer command and the allocation fails partway through, the error cleanup frees the allocated memory but leaves stale accounting counters and a dangling pointer in the command context. Later queue-credit accounting subtracts incorrect values, and the dangling pointer may be dereferenced when the context is reused, corrupting kernel heap memory. The fix saves the original counter values before allocation begins and, on failure, restores them and clears the pointer after freeing, returning the context to a clean state. An attacker with access to the RDMA fabric can trigger this by sending a crafted multi-buffer SCSI command that causes a partial allocation failure; no operating-system privileges are needed beyond fabric access.