Patch "mmc: tmio: avoid concurrent runs of mmc_request_done()" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    mmc: tmio: avoid concurrent runs of mmc_request_done()

to the 5.15-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:
     mmc-tmio-avoid-concurrent-runs-of-mmc_request_done.patch
and it can be found in the queue-5.15 subdirectory.

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



commit 3636d70971e3aad1b21a82985f6b63f9944976db
Author: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
Date:   Tue Mar 5 11:42:56 2024 +0100

    mmc: tmio: avoid concurrent runs of mmc_request_done()
    
    [ Upstream commit e8d1b41e69d72c62865bebe8f441163ec00b3d44 ]
    
    With the to-be-fixed commit, the reset_work handler cleared 'host->mrq'
    outside of the spinlock protected critical section. That leaves a small
    race window during execution of 'tmio_mmc_reset()' where the done_work
    handler could grab a pointer to the now invalid 'host->mrq'. Both would
    use it to call mmc_request_done() causing problems (see link below).
    
    However, 'host->mrq' cannot simply be cleared earlier inside the
    critical section. That would allow new mrqs to come in asynchronously
    while the actual reset of the controller still needs to be done. So,
    like 'tmio_mmc_set_ios()', an ERR_PTR is used to prevent new mrqs from
    coming in but still avoiding concurrency between work handlers.
    
    Reported-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx>
    Closes: https://lore.kernel.org/all/20240220061356.3001761-1-dirk.behme@xxxxxxxxxxxx/
    Fixes: df3ef2d3c92c ("mmc: protect the tmio_mmc driver against a theoretical race")
    Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
    Tested-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx>
    Reviewed-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx>
    Cc: stable@xxxxxxxxxxxxxxx # 3.0+
    Link: https://lore.kernel.org/r/20240305104423.3177-2-wsa+renesas@xxxxxxxxxxxxxxxxxxxx
    Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/mmc/host/tmio_mmc_core.c b/drivers/mmc/host/tmio_mmc_core.c
index 437048bb80273..5024cae411d3a 100644
--- a/drivers/mmc/host/tmio_mmc_core.c
+++ b/drivers/mmc/host/tmio_mmc_core.c
@@ -259,6 +259,8 @@ static void tmio_mmc_reset_work(struct work_struct *work)
 	else
 		mrq->cmd->error = -ETIMEDOUT;
 
+	/* No new calls yet, but disallow concurrent tmio_mmc_done_work() */
+	host->mrq = ERR_PTR(-EBUSY);
 	host->cmd = NULL;
 	host->data = NULL;