linux-kernel - Re: [PATCH] fs/vboxsf: Replace kmap() with kmap_local

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <cedbd75d-4a0f-74fb-3a6e-547862cc431e@redhat.com>
Date:   Tue, 27 Jun 2023 20:04:58 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>,
        Sumitra Sharma <sumitraartsy@...il.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ira Weiny <ira.weiny@...el.com>,
        Fabio <fmdefrancesco@...il.com>, Deepak R Varma <drv@...lo.com>
Subject: Re: [PATCH] fs/vboxsf: Replace kmap() with kmap_local_{page, folio}()

Hi Matthew,

On 6/27/23 19:48, Matthew Wilcox wrote:
> On Tue, Jun 27, 2023 at 06:51:15AM -0700, Sumitra Sharma wrote:
>> +++ b/fs/vboxsf/file.c
>> @@ -234,7 +234,7 @@ static int vboxsf_read_folio(struct file *file, struct folio *folio)
>>  	u8 *buf;
>>  	int err;
>>  
>> -	buf = kmap(page);
>> +	buf = kmap_local_folio(folio, off);
> 
> Did you test this?  'off' is the offset in the _file_.  Whereas
> kmap_local_folio() takes the offset within the _folio_.  They have
> different types (loff_t vs size_t) to warn you that they're different
> things.


Ah yes you are completely right, off is the offset in the file
and buf should point to the *start* of a mapping of the page.

Regards,

Hans