linux-kernel - [PATCH] kobject: don't use WARN for registration failures

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Message-Id: <20180411152243.101848-1-dvyukov@google.com>
Date:   Wed, 11 Apr 2018 17:22:43 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     gregkh@...uxfoundation.org
Cc:     linux-kernel@...r.kernel.org, Dmitry Vyukov <dvyukov@...gle.com>
Subject: [PATCH] kobject: don't use WARN for registration failures

This WARNING proved to be noisy. The function still returns an error
and callers should handle it. That's how most of kernel code works.
Downgrade the WARNING to pr_err() and leave WARNINGs for kernel bugs.

Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
Reported-by: syzbot+209c0f67f99fec8eb14b@...kaller.appspotmail.com
Reported-by: syzbot+7fb6d9525a4528104e05@...kaller.appspotmail.com
Reported-by: syzbot+2e63711063e2d8f9ea27@...kaller.appspotmail.com
Reported-by: syzbot+de73361ee4971b6e6f75@...kaller.appspotmail.com

---

For the record, here are only currently open syzbot bugs for this WARNING
(not counting older bugs and various duplicates). None of them were
acted on:

WARNING: kobject bug in gfs2_sys_fs_add
https://syzkaller.appspot.com/bug?id=057673a56dab61b3a447989b67f10b205111c8f4

WARNING: kobject bug in br_add_if
https://syzkaller.appspot.com/bug?id=3e0339080acd6a2a350a900bc6533b03f5498490

WARNING: kobject bug in netdev_queue_update_kobjects
https://syzkaller.appspot.com/bug?id=86a8e2ab50527d5a5eb4fad2fc15df609f22d86a

WARNING: kobject bug in device_add
https://syzkaller.appspot.com/bug?id=57eba87aff7669512fb68e56a932b01805342d13

For context see discussion here:
https://groups.google.com/d/msg/syzkaller-bugs/JZ9QSEaA_HA/wWvpywtBBQAJ
---
 lib/kobject.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/lib/kobject.c b/lib/kobject.c
index e1d1f290bf35..18989b5b3b56 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -233,13 +233,12 @@ static int kobject_add_internal(struct kobject *kobj)
 
 		/* be noisy on error issues */
 		if (error == -EEXIST)
-			WARN(1,
-			     "%s failed for %s with -EEXIST, don't try to register things with the same name in the same directory.\n",
-			     __func__, kobject_name(kobj));
+			pr_err("%s failed for %s with -EEXIST, don't try to register things with the same name in the same directory.\n",
+			       __func__, kobject_name(kobj));
 		else
-			WARN(1, "%s failed for %s (error: %d parent: %s)\n",
-			     __func__, kobject_name(kobj), error,
-			     parent ? kobject_name(parent) : "'none'");
+			pr_err("%s failed for %s (error: %d parent: %s)\n",
+			       __func__, kobject_name(kobj), error,
+			       parent ? kobject_name(parent) : "'none'");
 	} else
 		kobj->state_in_sysfs = 1;
 
-- 
2.17.0.484.g0c8726318c-goog