linux-kernel - Re: Bug: broken /proc/kcore in 6.13

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Message-ID: <3719ee8a-38ef-4aaa-aca4-b6d82df51661@orange.com>
Date: Fri, 17 Jan 2025 20:27:56 +0100
From: Alexandre Ferrieux <alexandre.ferrieux@...il.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Alexandre Ferrieux <alexandre.ferrieux@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>, linux-trace-users@...r.kernel.org,
 LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
 Mike Rapoport <rppt@...nel.org>
Subject: Re: Bug: broken /proc/kcore in 6.13

On 17/01/2025 19:13, Lorenzo Stoakes wrote:
> 
> +cc Mike
> 
> OK so nothing to worry about here - the feature that causes this problem
> has been completely disabled. This may not be in Linus's tree yet but will
> be for 6.13 release [0].
> 
> I think the vread_iter() check for 0 can wait for 6.14, as once the area of
> memory is identified this should never happen, but we do want to pick up on
> it, with a WARN_ON_ONCE() to catch stuff like this right away.
> 
> Thanks so much for the repro, though I observed the 'core /proc/kcore'
> command freezing up before any 'disass' in my qemu setup, interestingly!
> 
> [0]:https://lore.kernel.org/all/20250113112934.GA8385@noisy.programming.kicks-ass.net/

Thank you for the fast fix, I'm back on track :)

 Dump of assembler code for function ice_process_skb_fields:
    0xffffffffc0fc1eb0 <+0>:     nopw   (%rax)
    0xffffffffc0fc1eb4 <+4>:     nopl   0x0(%rax,%rax,1)
    0xffffffffc0fc1eb9 <+9>:     push   %r14
    0xffffffffc0fc1ebb <+11>:    push   %r13

-Alex