From d6211ebbdaa541af197b50b8dd8f22642ce0b87f Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 13 Feb 2025 08:24:23 -0700 Subject: [PATCH] io_uring/uring_cmd: unconditionally copy SQEs at prep time This isn't generally necessary, but conditions have been observed where SQE data is accessed from the original SQE after prep has been done and outside of the initial issue. Opcode prep handlers must ensure that any SQE related data is stable beyond the prep phase, but uring_cmd is a bit special in how it handles the SQE which makes it susceptible to reading stale data. If the application has reused the SQE before the original completes, then that can lead to data corruption. Down the line we can relax this again once uring_cmd has been sanitized a bit, and avoid unnecessarily copying the SQE. Fixes: 5eff57fa9f3a ("io_uring/uring_cmd: defer SQE copying until it's needed") Reported-by: Caleb Sander Mateos Reviewed-by: Caleb Sander Mateos Reviewed-by: Li Zetao Signed-off-by: Jens Axboe --- io_uring/uring_cmd.c | 34 +++++++++++----------------------- 1 file changed, 11 insertions(+), 23 deletions(-) diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c index 8af7780407b7..e6701b7aa147 100644 --- a/io_uring/uring_cmd.c +++ b/io_uring/uring_cmd.c @@ -165,15 +165,6 @@ void io_uring_cmd_done(struct io_uring_cmd *ioucmd, ssize_t ret, u64 res2, } EXPORT_SYMBOL_GPL(io_uring_cmd_done); -static void io_uring_cmd_cache_sqes(struct io_kiocb *req) -{ - struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd); - struct io_uring_cmd_data *cache = req->async_data; - - memcpy(cache->sqes, ioucmd->sqe, uring_sqe_size(req->ctx)); - ioucmd->sqe = cache->sqes; -} - static int io_uring_cmd_prep_setup(struct io_kiocb *req, const struct io_uring_sqe *sqe) { @@ -185,10 +176,15 @@ static int io_uring_cmd_prep_setup(struct io_kiocb *req, return -ENOMEM; cache->op_data = NULL; - ioucmd->sqe = sqe; - /* defer memcpy until we need it */ - if (unlikely(req->flags & REQ_F_FORCE_ASYNC)) - io_uring_cmd_cache_sqes(req); + /* + * Unconditionally cache the SQE for now - this is only needed for + * requests that go async, but prep handlers must ensure that any + * sqe data is stable beyond prep. Since uring_cmd is special in + * that it doesn't read in per-op data, play it safe and ensure that + * any SQE data is stable beyond prep. This can later get relaxed. + */ + memcpy(cache->sqes, sqe, uring_sqe_size(req->ctx)); + ioucmd->sqe = cache->sqes; return 0; } @@ -251,16 +247,8 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags) } ret = file->f_op->uring_cmd(ioucmd, issue_flags); - if (ret == -EAGAIN) { - struct io_uring_cmd_data *cache = req->async_data; - - if (ioucmd->sqe != cache->sqes) - io_uring_cmd_cache_sqes(req); - return -EAGAIN; - } else if (ret == -EIOCBQUEUED) { - return -EIOCBQUEUED; - } - + if (ret == -EAGAIN || ret == -EIOCBQUEUED) + return ret; if (ret < 0) req_set_fail(req); io_req_uring_cleanup(req, issue_flags);