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@de.bosch.com>
Closes: https://lore.kernel.org/all/20240220061356.3001761-1-dirk.behme@de.bosch.com/
Fixes: df3ef2d3c92c ("mmc: protect the tmio_mmc driver against a theoretical race")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Dirk Behme <dirk.behme@de.bosch.com>
Reviewed-by: Dirk Behme <dirk.behme@de.bosch.com>
Cc: stable@vger.kernel.org # 3.0+
Link: https://lore.kernel.org/r/20240305104423.3177-2-wsa+renesas@sang-engineering.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/mmc/host/tmio_mmc_core.c b/drivers/mmc/host/tmio_mmc_core.c
index be7f18fd4836ab2943de311523d7c0c4493eac75..c253d176db69180b9da70036e3594ab587547d0c 100644 (file)
--- 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;