On Tue, 5 Mar 2024 at 11:44, Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx> wrote: > > 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+ Applied for fixes, thanks! Kind regards Uffe > --- > > Change since v1/RFT: added Dirk's tags and stable tag > > @Ulf: this is nasty, subtle stuff. Would be awesome to have it in 6.8 > already! > > drivers/mmc/host/tmio_mmc_core.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/mmc/host/tmio_mmc_core.c b/drivers/mmc/host/tmio_mmc_core.c > index be7f18fd4836..c253d176db69 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; > > -- > 2.43.0 >
