@samitouri / QOSamiQemu / commits / 4b615eaa1b

hw/9pfs: add response_buffer_size transport callback

Add a new callback to the V9fsTransport interface that allows each transport to provide the real size of its current response buffer. This is needed for subsequent safety guards that will limit generated responses appropriately before trying to allocate, generate, and send a response to guest. This is especially required for request handlers that need to allocate dynamic and potentially large host memory for generating a response. These safety guards are mandatory to counter bad clients that try to trick server by supplying response buffers being smaller than the previously negotiated msize value. Link: https://lore.kernel.org/qemu-devel/703ed8ce4401c4550ef2cd99f30ab808665d6e85.1781287774.git.qemu_oss@crudebyte.com Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>

Christian Schoenebeck committed Jun 12, 2026 at 20:22 UTC 4b615eaa1be4a54fb677c302e1a86fe09a94aecd

1 file changed +1

hw/9pfs/9p.h

@@ -482,6 +482,7 @@ struct V9fsTransport {

482 unsigned int *pniov, size_t size);

483 void (*push_and_notify)(V9fsPDU *pdu);

484 size_t (*msize_limit)(V9fsState *s);

485 + size_t (*response_buffer_size)(V9fsPDU *pdu);

486 };

487

488 #endif