Re: [PATCH stable 5.15] mm/memory: add non-anonymous page check in the copy_present_page()

[David Hildenbrand <david@redhat.com>]

On 13.11.24 17:31, Vlastimil Babka wrote:
> From: Yuanzheng Song <songyuanzheng@huawei.com>
> 
> 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:1052!
> Internal error: Oops - BUG: 0 [#1] SMP
> Modules linked in:
> CPU: 4 PID: 4652 Comm: test Not tainted 5.15.75 #1
> Hardware name: linux,dummy-virt (DT)
> pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : __page_set_anon_rmap+0xc0/0xe8
> lr : __page_set_anon_rmap+0xc0/0xe8
> sp : ffff80000e773860
> x29: ffff80000e773860 x28: fffffc13cf006ec0 x27: ffff04f3ccd68000
> x26: ffff04f3c5c33248 x25: 0000000010100073 x24: ffff04f3c53c0a80
> x23: 0000000020000000 x22: 0000000000000001 x21: 0000000020000000
> x20: fffffc13cf006ec0 x19: 0000000000000000 x18: 0000000000000000
> x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
> x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
> x11: 0000000000000000 x10: 0000000000000000 x9 : ffffdddc5581377c
> x8 : 0000000000000000 x7 : 0000000000000011 x6 : ffff2717a8433000
> x5 : ffff80000e773810 x4 : ffffdddc55400000 x3 : 0000000000000000
> x2 : ffffdddc56b20000 x1 : ffff04f3c9a48040 x0 : 0000000000000000
> Call trace:
>   __page_set_anon_rmap+0xc0/0xe8
>   page_add_new_anon_rmap+0x13c/0x200
>   copy_pte_range+0x6b8/0x1018
>   copy_page_range+0x3a8/0x5e0
>   dup_mmap+0x3a0/0x6e8
>   dup_mm+0x78/0x140
>   copy_process+0x1528/0x1b08
>   kernel_clone+0xac/0x610
>   __do_sys_clone+0x78/0xb0
>   __arm64_sys_clone+0x30/0x40
>   invoke_syscall+0x68/0x170
>   el0_svc_common.constprop.0+0x80/0x250
>   do_el0_svc+0x48/0xb8
>   el0_svc+0x48/0x1a8
>   el0t_64_sync_handler+0xb0/0xb8
>   el0t_64_sync+0x1a0/0x1a4
> Code: 97f899f4 f9400273 17ffffeb 97f899f1 (d4210000)
> ---[ end trace dc65e5edd0f362fa ]---
> Kernel panic - not syncing: Oops - BUG: Fatal exception
> SMP: stopping secondary CPUs
> Kernel Offset: 0x5ddc4d400000 from 0xffff800008000000
> PHYS_OFFSET: 0xfffffb0c80000000
> CPU features: 0x44000cf1,00000806
> Memory Limit: none
> ---[ end Kernel panic - not syncing: Oops - BUG: Fatal exception ]---
> 
> This problem has been fixed by the commit <fb3d824d1a46>
> ("mm/rmap: split page_dup_rmap() into page_dup_file_rmap()
> and page_try_dup_anon_rmap()"), but still exists in the
> linux-5.15.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().
> 
> Cc: stable@vger.kernel.org
> Fixes: 70e806e4e645 ("mm: Do early cow for pinned pages during fork() for ptes")
> Signed-off-by: Yuanzheng Song <songyuanzheng@huawei.com>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> ---
> Hi, this was posted in [1] but seems stable@ was not actually included
> in the recipients.
> The 5.10 version [2] was applied as 935a8b62021 but 5.15 is missing.
> 
> [1] https://lore.kernel.org/all/20221028075244.3112566-1-songyuanzheng@huawei.com/T/#u
> [2] https://lore.kernel.org/all/20221028030705.2840539-1-songyuanzheng@huawei.com/
> 
> 
>   mm/memory.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 6d058973a97e..4785aecca9a8 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -903,6 +903,17 @@ copy_present_page(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma
>   	if (likely(!page_needs_cow_for_dma(src_vma, page)))
>   		return 1;
>   
> +	/*
> +	 * The vma->anon_vma of the child process may be NULL
> +	 * because the entire vma does not contain anonymous pages.
> +	 * 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.
> +	 * Return 1 if the page is not an anonymous page.
> +	 */
> +	if (!PageAnon(page))
> +		return 1;
> +
>   	new_page = *prealloc;
>   	if (!new_page)
>   		return -EAGAIN;

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb