Boot stalls in v4.9.y to v5.4.y stable queues

Boot stalls in v4.9.y to v5.4.y stable queues

[Guenter Roeck]

Hi,

all stable release queues from v4.9.y up to v5.4.y have boot stall
problems. The culprit is the backport of commit d7ea0d9df2a6 ("net:
remove two BUG() from skb_checksum_help()"), specifically the following
code.

diff --git a/net/core/dev.c b/net/core/dev.c
index 47468fc5d0c9..d725ca4d4455 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2518,11 +2518,15 @@ int skb_checksum_help(struct sk_buff *skb)
...
-       BUG_ON(offset >= skb_headlen(skb));
+       ret = -EINVAL;
        ^^^^^^^^^^^^^^
+       if (WARN_ON_ONCE(offset >= skb_headlen(skb)))
+               goto out;
+

While that works fine in the upstream kernel since ret is subsequently
always overwritten, that is not the case in older kernels. In those,
the function now always returns -EINVAL.

Guenter

Re: Boot stalls in v4.9.y to v5.4.y stable queues

[Eric Dumazet]

On Thu, Jun 9, 2022 at 5:05 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> Hi,
>
> all stable release queues from v4.9.y up to v5.4.y have boot stall
> problems. The culprit is the backport of commit d7ea0d9df2a6 ("net:
> remove two BUG() from skb_checksum_help()"), specifically the following
> code.
>

Not sure why this patch has been backported.

It had no Fixes: tag, and was not a stable candidate.

> While that works fine in the upstream kernel since ret is subsequently
> always overwritten, that is not the case in older kernels. In those,
> the function now always returns -EINVAL.

Re: Boot stalls in v4.9.y to v5.4.y stable queues

[Guenter Roeck]

On 6/9/22 18:59, Eric Dumazet wrote:
> On Thu, Jun 9, 2022 at 5:05 PM Guenter Roeck <linux@roeck-us.net> wrote:
>>
>> Hi,
>>
>> all stable release queues from v4.9.y up to v5.4.y have boot stall
>> problems. The culprit is the backport of commit d7ea0d9df2a6 ("net:
>> remove two BUG() from skb_checksum_help()"), specifically the following
>> code.
>>
> 
> Not sure why this patch has been backported.
> 
> It had no Fixes: tag, and was not a stable candidate.
> 

Happens with lots of patches. Never ending discussion.

Guenter

>> While that works fine in the upstream kernel since ret is subsequently
>> always overwritten, that is not the case in older kernels. In those,
>> the function now always returns -EINVAL.

Re: Boot stalls in v4.9.y to v5.4.y stable queues

[Greg Kroah-Hartman]

On Thu, Jun 09, 2022 at 06:59:59PM -0700, Eric Dumazet wrote:
> On Thu, Jun 9, 2022 at 5:05 PM Guenter Roeck <linux@roeck-us.net> wrote:
> >
> > Hi,
> >
> > all stable release queues from v4.9.y up to v5.4.y have boot stall
> > problems. The culprit is the backport of commit d7ea0d9df2a6 ("net:
> > remove two BUG() from skb_checksum_help()"), specifically the following
> > code.
> >
> 
> Not sure why this patch has been backported.
> 
> It had no Fixes: tag, and was not a stable candidate.

Now dropped thanks.

greg k-h