Commit c8e50ece authored Jul 13, 2020 by Tetsuo Handa Committed by Greg Kroah-Hartman Oct 14, 2020

driver core: Fix probe_count imbalance in really_probe()

commit b292b50b0efcc7095d8bf15505fba6909bb35dce upstream.

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=25c833f1983c9c1d512f4ff860dd0d7f5a2e2c0f



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.ne.jp


[iwamatsu: Drop patch for deferred_probe_timeout_work_func()]
Signed-off-by: Nobuhiro Iwamatsu (CIP) <nobuhiro1.iwamatsu@toshiba.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent fed8fd79

drivers/base/dd.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -285,7 +285,8 @@ 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;
		}

		dev->driver = drv;
		@@ -363,7 +364,7 @@ probe_failed:
		ret = 0;
		done:
		atomic_dec(&probe_count);
		wake_up(&probe_waitqueue);
		wake_up_all(&probe_waitqueue);
		return ret;
		}