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Date: Tue, 27 May 2025 13:47:17 +0800
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Subject: Re: [PATCH] Loongarch:Fixed up panic cause by a NULL-pmd
To: Tianyang Zhang <zhangtianyang@loongson.cn>, chenhuacai@kernel.org,
 kernel@xen0n.name, zhanghongchen@loongson.cn, wangming01@loongson.cn,
 peterx@redhat.com
Cc: loongarch@lists.linux.dev, linux-kernel@vger.kernel.org
References: <20250526065512.13215-1-zhangtianyang@loongson.cn>
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From: Yanteng Si <si.yanteng@linux.dev>
In-Reply-To: <20250526065512.13215-1-zhangtianyang@loongson.cn>
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在 5/26/25 2:55 PM, Tianyang Zhang 写道:
> From: zhangtianyang <zhangtianyang@loongson.cn>
> 
> Fixes: bd51834d1cf6 ("LoongArch: Return NULL from huge_pte_offset() for invalid PMD")
> ERROR INFO:
> 
> CPU 25 Unable to handle kernel paging request at virtual address 0x0
>           ...
>   Call Trace:
>   [<900000000023c30c>] huge_pte_offset+0x3c/0x58
>   [<900000000057fd4c>] hugetlb_follow_page_mask+0x74/0x438
>   [<900000000051fee8>] __get_user_pages+0xe0/0x4c8
>   [<9000000000522414>] faultin_page_range+0x84/0x380
>   [<9000000000564e8c>] madvise_vma_behavior+0x534/0xa48
>   [<900000000056689c>] do_madvise+0x1bc/0x3e8
>   [<9000000000566df4>] sys_madvise+0x24/0x38
>   [<90000000015b9e88>] do_syscall+0x78/0x98
>   [<9000000000221f18>] handle_syscall+0xb8/0x158
> 

> In some cases, pmd may be NULL and rely on NULL as the return value
> for processing, so it is necessary to determine this situation here

Your description is a bit vague. Could you please specify
on which machines and in what scenarios this bug can be
reproduced? I believe such information should be included
in the commit message.

Thanks,
Yanteng