io_uring/net: don't overconsume buffers when using MSG_TRUNC

When a recv/recvmsg is issued with MSG_TRUNC and the incoming packet is
larger than the provided buffer, the net layer returns the full length
of the packet rather than the number of bytes actually copied into the
buffer.  As a result, io_uring advances more of the provided buffer ring
than was actually filled.  Use the actual filled region size to consume
the buffer, but still return the full size to preserve MSG_TRUNC
semantics.

Take care with multishot, because that seems to already truncate the
consumption based on the available payload size.

This was reported in https://github.com/axboe/liburing/issues/1619.

Fixes: ae98dbf43d75 ("io_uring/kbuf: add support for incremental buffer consumption")
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260728191454.1850326-1-krisman@suse.de
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
Link: https://patch.msgid.link/20260902230041.1320658-3-krisman@suse.de
[axboe: fold in size_t unsigned fix]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

0 files changed, 0 insertions, 0 deletions