linux-kernel - Re: [Bug report] hash_name() may cross page boundary and trigger sleep in RCU context

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Message-ID: <7970e1c4-88d5-42ef-b8cf-ed50d27fedcc@huaweicloud.com>
Date: Mon, 1 Dec 2025 10:38:49 +0800
From: Zizhi Wo <wozizhi@...weicloud.com>
To: Al Viro <viro@...iv.linux.org.uk>, Zizhi Wo <wozizhi@...weicloud.com>
Cc: Will Deacon <will@...nel.org>,
 Linus Torvalds <torvalds@...ux-foundation.org>, jack@...e.com,
 brauner@...nel.org, hch@....de, akpm@...ux-foundation.org,
 linux@...linux.org.uk, linux-fsdevel@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 linux-arm-kernel@...ts.infradead.org, yangerkun@...wei.com,
 wangkefeng.wang@...wei.com, pangliyuan1@...wei.com, xieyuanbin1@...wei.com
Subject: Re: [Bug report] hash_name() may cross page boundary and trigger
 sleep in RCU context



在 2025/11/29 11:55, Al Viro 写道:
> On Sat, Nov 29, 2025 at 09:02:27AM +0800, Zizhi Wo wrote:
> 
>> Thank you very much for the answer. For the vmalloc area, I checked the
>> call points on the vfs side, such as dentry_string_cmp() or hash_name().
>> Their "names addr" are all assigned by kmalloc(), so there should be no
>> corresponding issues. But I'm not familiar with the other calling
>> points...
> 
> Pathname might be a symlink body, sitting in page cache or whatever
> ->get_link() has returned...
> 


Thanks for the additional explanation — I indeed hadn't considered
symlinks. But if the data is in the page cache, as I understand it, its
address wouldn't be in the vmalloc area, right? However, for other
.get_link implementations, it's true that there's no guarantee.

Thanks,
Zizhi Wo