The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From b292b50b0efcc7095d8bf15505fba6909bb35dce Mon Sep 17 00:00:00 2001
From: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp Date: Mon, 13 Jul 2020 11:12:54 +0900 Subject: [PATCH] driver core: Fix probe_count imbalance in really_probe()
syzbot is reporting hung task in wait_for_device_probe() [1]. At least, we always need to decrement probe_count if we incremented probe_count in really_probe().
However, since I can't find "Resources present before probing" message in the console log, both "this message simply flowed off" and "syzbot is not hitting this path" will be possible. Therefore, while we are at it, let's also prepare for concurrent wait_for_device_probe() calls by replacing wake_up() with wake_up_all().
[1] https://syzkaller.appspot.com/bug?id=25c833f1983c9c1d512f4ff860dd0d7f5a2e2c0...
Reported-by: syzbot syzbot+805f5f6ae37411f15b64@syzkaller.appspotmail.com Fixes: 7c35e699c88bd607 ("driver core: Print device when resources present in really_probe()") Cc: Geert Uytterhoeven geert+renesas@glider.be Signed-off-by: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp Cc: stable stable@kernel.org Link: https://lore.kernel.org/r/20200713021254.3444-1-penguin-kernel@I-love.SAKURA... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
diff --git a/drivers/base/dd.c b/drivers/base/dd.c index 2306b481109a..fce8e35b6367 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -276,7 +276,7 @@ static void deferred_probe_timeout_work_func(struct work_struct *work)
list_for_each_entry_safe(private, p, &deferred_probe_pending_list, deferred_probe) dev_info(private->device, "deferred probe pending\n"); - wake_up(&probe_timeout_waitqueue); + wake_up_all(&probe_timeout_waitqueue); } static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
@@ -498,7 +498,8 @@ static int really_probe(struct device *dev, struct device_driver *drv) drv->bus->name, __func__, drv->name, dev_name(dev)); if (!list_empty(&dev->devres_head)) { dev_crit(dev, "Resources present before probing\n"); - return -EBUSY; + ret = -EBUSY; + goto done; }
re_probe: @@ -627,7 +628,7 @@ static int really_probe(struct device *dev, struct device_driver *drv) ret = 0; done: atomic_dec(&probe_count); - wake_up(&probe_waitqueue); + wake_up_all(&probe_waitqueue); return ret; }