linux-kernel - Re: [Ocfs2-devel] [PATCH] ocfs2: check new file size on fallocate call

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Date:   Thu, 1 Jun 2023 09:23:06 +0800
From:   Joseph Qi <joseph.qi@...ux.alibaba.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Luís Henriques <lhenriques@...e.de>
Cc:     Luís Henriques via Ocfs2-devel 
        <ocfs2-devel@....oracle.com>, Mark Fasheh <mark@...heh.com>,
        Joel Becker <jlbec@...lplan.org>,
        Heming Zhao <heming.zhao@...e.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [Ocfs2-devel] [PATCH] ocfs2: check new file size on fallocate
 call



On 6/1/23 6:11 AM, Andrew Morton wrote:
> On Mon, 29 May 2023 16:26:45 +0100 Luís Henriques via Ocfs2-devel <ocfs2-devel@....oracle.com> wrote:
> 
>> When changing a file size with fallocate() the new size isn't being
>> checked.  In particular, the FSIZE ulimit isn't being checked, which makes
>> fstest generic/228 fail.  Simply adding a call to inode_newsize_ok() fixes
>> this issue.
>>
>> ...
>>
>> --- a/fs/ocfs2/file.c
>> +++ b/fs/ocfs2/file.c
>> @@ -2100,14 +2100,20 @@ static long ocfs2_fallocate(struct file *file, int mode, loff_t offset,
>>  	struct ocfs2_space_resv sr;
>>  	int change_size = 1;
>>  	int cmd = OCFS2_IOC_RESVSP64;
>> +	int ret = 0;
>>  
>>  	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
>>  		return -EOPNOTSUPP;
>>  	if (!ocfs2_writes_unwritten_extents(osb))
>>  		return -EOPNOTSUPP;
>>  
>> -	if (mode & FALLOC_FL_KEEP_SIZE)
>> +	if (mode & FALLOC_FL_KEEP_SIZE) {
>>  		change_size = 0;
>> +	} else {
>> +		ret = inode_newsize_ok(inode, offset + len);
>> +		if (ret)
>> +			return ret;
>> +	}
>>  
> 
> So userspace can exceed rlimit(RLIMIT_FSIZE).
> 
> Do we think this flaw is serious enough to justify backporting the fix
> into earlier -stable kernels?

I think it's worth ccing stable kernel as well.

Thanks,
Joseph