From: Stephen Boyd swboyd@chromium.org
commit 10252bae863d09b9648bed2e035572d207200ca1 upstream.
There's a chance that the IDA allocated in mmc_alloc_host() is not freed for some time because it's freed as part of a class' release function (see mmc_host_classdev_release() where the IDA is freed). If another thread is holding a reference to the class, then only once all balancing device_put() calls (in turn calling kobject_put()) have been made will the IDA be released and usable again.
Normally this isn't a problem because the kobject is released before anything else that may want to use the same number tries to again, but with CONFIG_DEBUG_KOBJECT_RELEASE=y and OF aliases it becomes pretty easy to try to allocate an alias from the IDA twice while the first time it was allocated is still pending a call to ida_simple_remove(). It's also possible to trigger it by using CONFIG_DEBUG_KOBJECT_RELEASE and probe defering a driver at boot that calls mmc_alloc_host() before trying to get resources that may defer likes clks or regulators.
Instead of allocating from the IDA in this scenario, let's just skip it if we know this is an OF alias. The number is already "claimed" and devices that aren't using OF aliases won't try to use the claimed numbers anyway (see mmc_first_nonreserved_index()). This should avoid any issues with mmc_alloc_host() returning failures from the ida_simple_get() in the case that we're using an OF alias.
Cc: Matthias Schiffer matthias.schiffer@ew.tq-group.com Cc: Sujit Kautkar sujitka@chromium.org Reported-by: Zubin Mithra zsm@chromium.org Fixes: fa2d0aa96941 ("mmc: core: Allow setting slot index via device tree alias") Signed-off-by: Stephen Boyd swboyd@chromium.org Link: https://lore.kernel.org/r/20210623075002.1746924-3-swboyd@chromium.org Cc: stable@vger.kernel.org Signed-off-by: Ulf Hansson ulf.hansson@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/mmc/core/host.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-)
--- a/drivers/mmc/core/host.c +++ b/drivers/mmc/core/host.c @@ -74,7 +74,8 @@ static void mmc_host_classdev_release(st { struct mmc_host *host = cls_dev_to_mmc_host(dev); wakeup_source_unregister(host->ws); - ida_simple_remove(&mmc_host_ida, host->index); + if (of_alias_get_id(host->parent->of_node, "mmc") < 0) + ida_simple_remove(&mmc_host_ida, host->index); kfree(host); }
@@ -436,7 +437,7 @@ static int mmc_first_nonreserved_index(v */ struct mmc_host *mmc_alloc_host(int extra, struct device *dev) { - int err; + int index; struct mmc_host *host; int alias_id, min_idx, max_idx;
@@ -449,20 +450,19 @@ struct mmc_host *mmc_alloc_host(int extr
alias_id = of_alias_get_id(dev->of_node, "mmc"); if (alias_id >= 0) { - min_idx = alias_id; - max_idx = alias_id + 1; + index = alias_id; } else { min_idx = mmc_first_nonreserved_index(); max_idx = 0; - }
- err = ida_simple_get(&mmc_host_ida, min_idx, max_idx, GFP_KERNEL); - if (err < 0) { - kfree(host); - return NULL; + index = ida_simple_get(&mmc_host_ida, min_idx, max_idx, GFP_KERNEL); + if (index < 0) { + kfree(host); + return NULL; + } }
- host->index = err; + host->index = index;
dev_set_name(&host->class_dev, "mmc%d", host->index); host->ws = wakeup_source_register(NULL, dev_name(&host->class_dev));