TCPIP: make the return value of network_socket_accept_tcp more expressive - #107
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TCPIP: make the return value of network_socket_accept_tcp more expressive#107nding0405 wants to merge 1 commit into
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…sive The network_socket_accept_tcp function can only return either a valid sealed capability or an untagged nullptr, so the caller cannot distinguish a timeout from an out-of-memory failure. Change it so that it can return an invalid capability that encodes the error code.
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This patch completes the fix for issue CHERIoT-Platform#104. PR CHERIoT-Platform#107 added an ephemeral claim in with_sealed_socket(), protecting the SealedSocket wrapper until the first cross-compartment call. In network_socket_close(), that protection ends at heap_can_free(). In the post-reset close path, the socket lock cannot be acquired, so any later dereference of the wrapper may race with another thread freeing the wrapper and cause a Use-After-Free. The normal close path is not affected because the wrapper remains protected by socketLock. To remove this race, the fields needed after heap_can_free() are copied from the wrapper before the cross call, and the wrapper is not dereferenced afterward in the post-reset path. The raw FreeRTOS socket is also vulnerable in rawSocket->ucProtocol; because this value is needed only for the normal close path, but the current codebase make it accesible for both nomal close and post-reset close, ane the later path can produce an UAF on that line of code. Thus, to fix this, the dereference is moved inside the lock-protected branch. These changes eliminate both wrapper and raw-socket UAF from the unprotected post-reset path.
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The network_socket_accept_tcp function can only return either a valid sealed capability or an untagged nullptr, so the caller cannot distinguish a timeout from an out-of-memory failure. Change it so that it can return an invalid capability that encodes the error code.