linux-kernel - [PATCH] regulator: fix crash caused by null driver data

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Message-Id: <20180919213051.199105-1-yuzhao@google.com>
Date:   Wed, 19 Sep 2018 15:30:51 -0600
From:   Yu Zhao <yuzhao@...gle.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Liam Girdwood <lgirdwood@...il.com>, linux-kernel@...r.kernel.org,
        Yu Zhao <yuzhao@...gle.com>
Subject: [PATCH] regulator: fix crash caused by null driver data

dev_set_drvdata() needs to be called before device_register()
exposes device to userspace. Otherwise kernel crashes after it
gets null pointer from dev_get_drvdata() when userspace tries
to access sysfs entries.

[   25.566073] general protection fault: 0000 [#1] PREEMPT SMP KASAN NOPTI
[   25.621976] gsmi: Log Shutdown Reason 0x03
<snipped>
[   25.747085] Call Trace:
[   25.749532]  name_show+0x51/0x6f
[   25.752760]  dev_attr_show+0x59/0xa0
[   25.756333]  ? device_namespace+0x9e/0x9e
[   25.760339]  sysfs_kf_seq_show+0x228/0x33b
[   25.764434]  seq_read+0x74f/0xd58
[   25.767747]  ? set_track+0x63/0xfa
[   25.771148]  ? kzalloc+0xf/0xf
[   25.774200]  ? _copy_to_user+0x87/0x9a
[   25.777947]  __vfs_read+0x106/0x320
[   25.781433]  ? mandatory_lock+0x94/0x94
[   25.785267]  ? fsnotify_unmount_inodes+0x17d/0x17d
[   25.790053]  ? inode_security+0x17/0x40
[   25.793885]  ? selinux_file_permission+0x176/0x342
[   25.798670]  ? security_file_permission+0x77/0x98
[   25.803369]  vfs_read+0xf3/0x197
[   25.806595]  SyS_read+0xfa/0x19b
[   25.809822]  ? file_end_write+0x91/0x91
[   25.813653]  ? filp_close+0xdb/0x100
[   25.817225]  ? file_end_write+0x91/0x91
[   25.821057]  do_syscall_64+0x184/0x1bb
[   25.824804]  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
<snipped>
[   25.895502] RIP: rdev_get_name+0x29/0xa5 RSP: ffff8801d45779f0
[   26.550863] ---[ end trace fb2a7bb4f63aeba5 ]---

Signed-off-by: Yu Zhao <yuzhao@...gle.com>
---
 drivers/regulator/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 5f2218c67edf..69565ff65800 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -4404,13 +4404,13 @@ regulator_register(const struct regulator_desc *regulator_desc,
 	    !rdev->desc->fixed_uV)
 		rdev->is_switch = true;
 
+	dev_set_drvdata(&rdev->dev, rdev);
 	ret = device_register(&rdev->dev);
 	if (ret != 0) {
 		put_device(&rdev->dev);
 		goto unset_supplies;
 	}
 
-	dev_set_drvdata(&rdev->dev, rdev);
 	rdev_init_debugfs(rdev);
 
 	/* try to resolve regulators supply since a new one was registered */
-- 
2.19.0.397.gdd90340f6a-goog