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Date:   Wed, 26 Oct 2022 18:52:08 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Yuanzheng Song <songyuanzheng@huawei.com>
Cc:     akpm@linux-foundation.org, peterx@redhat.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH STABLE 5.10] mm/memory: add non-anonymous page check in
 the copy_present_page()
Message-ID: <Y1lluEIsa2T0wXE6@kroah.com>
References: <20221024094911.3054769-1-songyuanzheng@huawei.com>
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On Mon, Oct 24, 2022 at 09:49:11AM +0000, Yuanzheng Song wrote:
> The vma->anon_vma of the child process may be NULL because
> the entire vma does not contain anonymous pages. In this
> case, a BUG will occur when the copy_present_page() passes
> a copy of a non-anonymous page of that vma to the
> page_add_new_anon_rmap() to set up new anonymous rmap.
> 
> ------------[ cut here ]------------
> kernel BUG at mm/rmap.c:1044!
> Internal error: Oops - BUG: 0 [#1] SMP
> Modules linked in:
> CPU: 2 PID: 3617 Comm: test Not tainted 5.10.149 #1
> Hardware name: linux,dummy-virt (DT)
> pstate: 80000005 (Nzcv daif -PAN -UAO -TCO BTYPE=--)
> pc : __page_set_anon_rmap+0xbc/0xf8
> lr : __page_set_anon_rmap+0xbc/0xf8
> sp : ffff800014c1b870
> x29: ffff800014c1b870 x28: 0000000000000001
> x27: 0000000010100073 x26: ffff1d65c517baa8
> x25: ffff1d65cab0f000 x24: ffff1d65c416d800
> x23: ffff1d65cab5f248 x22: 0000000020000000
> x21: 0000000000000001 x20: 0000000000000000
> x19: fffffe75970023c0 x18: 0000000000000000
> x17: 0000000000000000 x16: 0000000000000000
> x15: 0000000000000000 x14: 0000000000000000
> x13: 0000000000000000 x12: 0000000000000000
> x11: 0000000000000000 x10: 0000000000000000
> x9 : ffffc3096d5fb858 x8 : 0000000000000000
> x7 : 0000000000000011 x6 : ffff5a5c9089c000
> x5 : 0000000000020000 x4 : ffff5a5c9089c000
> x3 : ffffc3096d200000 x2 : ffffc3096e8d0000
> x1 : ffff1d65ca3da740 x0 : 0000000000000000
> Call trace:
>  __page_set_anon_rmap+0xbc/0xf8
>  page_add_new_anon_rmap+0x1e0/0x390
>  copy_pte_range+0xd00/0x1248
>  copy_page_range+0x39c/0x620
>  dup_mmap+0x2e0/0x5a8
>  dup_mm+0x78/0x140
>  copy_process+0x918/0x1a20
>  kernel_clone+0xac/0x638
>  __do_sys_clone+0x78/0xb0
>  __arm64_sys_clone+0x30/0x40
>  el0_svc_common.constprop.0+0xb0/0x308
>  do_el0_svc+0x48/0xb8
>  el0_svc+0x24/0x38
>  el0_sync_handler+0x160/0x168
>  el0_sync+0x180/0x1c0
> Code: 97f8ff85 f9400294 17ffffeb 97f8ff82 (d4210000)
> ---[ end trace a972347688dc9bd4 ]---
> Kernel panic - not syncing: Oops - BUG: Fatal exception
> SMP: stopping secondary CPUs
> Kernel Offset: 0x43095d200000 from 0xffff800010000000
> PHYS_OFFSET: 0xffffe29a80000000
> CPU features: 0x08200022,61806082
> Memory Limit: none
> ---[ end Kernel panic - not syncing: Oops - BUG: Fatal exception ]---
> 
> This problem has been fixed by the fb3d824d1a46
> ("mm/rmap: split page_dup_rmap() into page_dup_file_rmap() and page_try_dup_anon_rmap()"),
> but still exists in the linux-5.10.y branch.
> 
> This patch is not applicable to this version because
> of the large version differences. Therefore, fix it by
> adding non-anonymous page check in the copy_present_page().
> 
> Fixes: 70e806e4e645 ("mm: Do early cow for pinned pages during fork() for ptes")
> Signed-off-by: Yuanzheng Song <songyuanzheng@huawei.com>
> ---
>  mm/memory.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)

We also need this in 5.15.y, right?  Can you provide a working version
for there so that no one upgrades from 5.10.y to 5.15.y and has a
regression?

I'll wait for that before taking this one.

thanks,

greg k-h