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[ Upstream commit 629e052d0c98e46dde9f0824f0aa437f678d9b8f ] If the hfi1 module is loaded with HFI1_CAP_SDMA off, a call to hfi1_write_iter() will dereference a NULL pointer and panic. A typical stack frame is: sdma_select_user_engine [hfi1] hfi1_user_sdma_process_request [hfi1] hfi1_write_iter [hfi1] do_iter_readv_writev do_iter_write vfs_writev do_writev do_syscall_64 The fix is to test for SDMA in hfi1_write_iter() and fail the I/O with EINVAL. Link: https://lore.kernel.org/r/20220520183706.48973.79803.stgit@awfm-01.cornelisnetworks.com Signed-off-by: Douglas Miller <doug.miller@cornelisnetworks.com> Signed-off-by: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com> Signed-off-by: Sasha Levin <sashal@kernel.org>