Patch "io_uring/uring_cmd: unconditionally copy SQEs at prep time" has been added to the 6.13-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    io_uring/uring_cmd: unconditionally copy SQEs at prep time

to the 6.13-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     io_uring-uring_cmd-unconditionally-copy-sqes-at-prep.patch
and it can be found in the queue-6.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 194e0f4bece4ed070886433c8ec3c3a5555085d6
Author: Jens Axboe <axboe@xxxxxxxxx>
Date:   Thu Feb 13 08:24:23 2025 -0700

    io_uring/uring_cmd: unconditionally copy SQEs at prep time
    
    [ Upstream commit d6211ebbdaa541af197b50b8dd8f22642ce0b87f ]
    
    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 <csander@xxxxxxxxxxxxxxx>
    Reviewed-by: Caleb Sander Mateos <csander@xxxxxxxxxxxxxxx>
    Reviewed-by: Li Zetao <lizetao1@xxxxxxxxxx>
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index 0ec58fcd6fc9b..8c44a5198414e 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -185,15 +185,6 @@ 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)
 {
@@ -204,10 +195,15 @@ static int io_uring_cmd_prep_setup(struct io_kiocb *req,
 	if (unlikely(!cache))
 		return -ENOMEM;
 
-	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;
 }
 
@@ -270,16 +266,8 @@ 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);