selftests/coredump: discard the right amount after the coredump request

read_coredump_req() gets the leftover wrong twice.

It takes the absolute difference of the two sizes, so a test binary that
knows a larger struct coredump_req than the kernel sends tries to discard
bytes that were never sent. And it hands recv() sizeof(buffer) instead of
the number of bytes it wants. So MSG_WAITALL waits for a whole page.
Either one blocks until the kernel closes the socket. Which it won't
because it is waiting for the coredump ack...

It's benign today because struct coredump_req hasn't grown. But let's fix
it for the future. Compute the leftover as what the kernel sent beyond
what was consumed.

Fixes: 59cd658eaf40 ("selftests/coredump: add coredump server selftests")
Link: https://patch.msgid.link/20260820-work-coredump-sparse-v2-4-ba32dd718c51@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

0 files changed, 0 insertions, 0 deletions