Re: [PATCH net-next 0/9] net: skbuff: convert most BUG_ON()s to WARN_ON_ONCE() and an error

[Fernando Fernandez Mancera <fmancera@suse.de>]

On 10/7/26 4:48 PM, Willem de Bruijn wrote:
> Josef Bacik wrote:
>> I'm going through and reducing BUG_ON() usage in areas that have created
>> the most problems for us.  89 commits in the tree quote "kernel BUG at
>> net/core/skbuff.c", 31 of them since 2024, and some of those could be
>> triggered from inside a user namespace.
>>
>> The first patch is a fix: skb_copy_and_csum_bits() leaves stale bytes
>> in a buffer headed for the wire when it hits unreadable frags.  The
>> BUG_ON() conversion of the same function needs the same handling, so
>> it's here rather than sent separately.
>>
>> The rest of the series converts 17 of the 19 BUG_ON()s in skbuff.c.
>> Each one becomes
>>
>> 	if (WARN_ON_ONCE(cond))
>> 		<error path>;
> 
> Good idea. I was thinking of doing exactly this sweep after addressing
> one case recently in commit ee1972def665 ("net: downgrade BUG_ON
> EIOCBQUEUED in sock_sendmsg_nosec")
> 
> Instead of WARN_ON_ONCE, which still triggers a panic on systems with
> panic_on_warn, DEBUG_NET_WARN_ON_ONCE?

I agree with using DEBUG_NET_WARN_ON_ONCE at least for paths that can be 
triggered from userspace. I did something similar in Netfilter subsystem 
not so long ago.