Messages in this thread | | | Date | Thu, 28 Jul 2022 19:14:43 +0300 | Subject | Re: [PATCH] can: j1939: Remove unnecessary WARN_ON_ONCE in j1939_sk_queue_activate_next_locked() | From | Fedor Pchelkin <> |
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Hello Oleksij,
I'm sorry for late answering.
On 20.07.2022 22:13, Oleksij Rempel wrote: >> Are you working on some system where this use case is valid?
No, we are fuzzing the kernel and analyzing different warnings and crashes.
On 20.07.2022 22:13, Oleksij Rempel wrote: > yes
Well, there is a long story about where and for which purposes the kernel warning macros should be correctly used and, overall, WARN_ON_ONCE is not intended for user-space notification.
Linus Torvalds wrote: > WARN_ON() should only be used for "This cannot happen, but if it does, > I want to know how we got here". > > So if that j1939 thing is something that can be triggered by a user, > then the backtrace should be reported to the driver maintainer, and > then either > > (a) the WARN_ON_ONCE() should just be removed ("ok, this can happen, > we understand why it can happen, and it's fine") > > (b) the problem the WARN_ON_ONCE() reports about should be made > impossible some way > > (c) it might be downgraded to a pr_warn() if people really want to > tell user space that "guys, you're doing something wrong" and it's > considered a useful warning.
So WARN_ON_ONCE should be replaced with a more gentle variant - I think pr_warn_once would suit this case. I've prepared a new patch for that, it will follow this email.
Could you also look at the patch - [PATCH] can: j1939: fix memory leak of skbs - which I sent you on 08.07.2022, please?
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