Sashiko reported [1] that 'Missing __GFP_ZERO in folio_alloc() causes uninitialized kernel memory to be exposed in the receive message buffer'. An ism dmb is receive-only, so the data is not leaked to a remote peer. In general the smc kernel module (dibs client) will only push newly received data to userspace. We still should not have uninitialized data in a receive buffer. Since commit 750afb08ca71 ("cross-tree: phase out dma_zalloc_coherent()") dma_alloc_coherent no longer required the __GFP_ZERO flag, but when commit 83781384a96b ("s390/ism: Properly fix receive message buffer allocation") switched to folio_alloc(), it should have added back the __GFP_ZERO flag. Add __GFP_ZERO flag and state in dibs.h that register_dbm() provides a zerorized buffer (dibs_lo already does). Link: https://lore.kernel.org/linux-s390/20260903143746.A5CC41F00A3A@smtp.kernel.org/ [1] Fixes: 83781384a96b ("s390/ism: Properly fix receive message buffer allocation") Signed-off-by: Alexandra Winter <wintera@linux.ibm.com> Reviewed-by: Julian Ruess <julianr@linux.ibm.com> Link: https://patch.msgid.link/20260928151420.383105-1-wintera@linux.ibm.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>