linux-kernel - Re: [linux-next:master] [mm] a0f2295a60: WARNING:at_mm/vma.c:#vma_merge_new

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Message-ID: <c7dc671c-0768-43b5-87b1-ca1654037202@lucifer.local>
Date: Tue, 27 Aug 2024 12:43:24 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: kernel test robot <oliver.sang@...el.com>
Cc: oe-lkp@...ts.linux.dev, lkp@...el.com,
        Linux Memory Management List <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Bert Karwatzki <spasswolf@....de>, Jiri Olsa <olsajiri@...il.com>,
        Kees Cook <kees@...nel.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Matthew Wilcox <willy@...radead.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Paul Moore <paul@...l-moore.com>,
        Sidhartha Kumar <sidhartha.kumar@...cle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org
Subject: Re: [linux-next:master] [mm]  a0f2295a60:
 WARNING:at_mm/vma.c:#vma_merge_new_range

On Tue, Aug 27, 2024 at 02:55:45PM GMT, kernel test robot wrote:
>
>
> Hello,
>
> kernel test robot noticed "WARNING:at_mm/vma.c:#vma_merge_new_range" on:
>
> commit: a0f2295a607c0e8a64893593432562444a58a70b ("mm: avoid using vma_merge() for new VMAs")
> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
>
> in testcase: trinity

[snip]

> [   28.048325][  T765] ------------[ cut here ]------------
> [ 28.048597][ T765] WARNING: CPU: 0 PID: 765 at mm/vma.c:524 vma_merge_new_range (mm/vma.c:524 (discriminator 1))

Hi, thanks for the report.

For the record this is the following CONFIG_DEBUG_VM check:

	/* vmi must point at or before the gap. */
	VM_WARN_ON(vma_iter_addr(vmg->vmi) > end);

Which I was able to determine fired due to copy_vma() unnecessarily
advancing the iterator if no previous VMA exists.

I have provided a fix-patch at [0] which should land in -next soon and
resolve this issue.

[0]:https://lore.kernel.org/linux-mm/c0ef6b6a-1c9b-4da2-a180-c8e1c73b1c28@lucifer.local/

[snip]