__issei_ham_process_ham_rsp() dispatches on hdr->cmd before the message
length is validated. The length comes from the firmware-owned DMA header
read in issei_dma_read(), which only bounds it from above, so firmware
sending a short bus message reaches the dispatch with less than
sizeof(struct ham_bus_message) bytes available.
For a zero-length message kmemdup() returns ZERO_SIZE_PTR, which passes
the NULL check in issei_dma_read(), and the dispatch dereferences it. A
length of one to three bytes gives a slab out-of-bounds read instead.
Reject bus messages shorter than the header before touching it, the way
the individual response handlers already validate their own length.
Fixes: 7bd4b9991d ("issei: implement main thread and ham messages")
Signed-off-by: Linmao Li <lilinmao@kylinos.cn>
Link: https://patch.msgid.link/20260731025952.3505287-1-lilinmao@kylinos.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
220190f97d