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Subject: Re: [PATCH] xfs: check the return value of krealloc() in
 xfs_uuid_mount
To:     Eric Sandeen <sandeen@sandeen.net>,
        "Darrick J. Wong" <darrick.wong@oracle.com>,
        <linux-xfs@vger.kernel.org>
CC:     <linux-kernel@vger.kernel.org>
References: <20201125065036.154312-1-miaoqinglang@huawei.com>
 <365b952c-7fea-3bc2-55ea-3f6b1c9f9142@sandeen.net>
From:   Qinglang Miao <miaoqinglang@huawei.com>
Message-ID: <9f998a9d-0684-6b45-009e-acf2e0ac4c85@huawei.com>
Date:   Thu, 26 Nov 2020 09:21:11 +0800
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在 2020/11/25 23:55, Eric Sandeen 写道:
> On 11/25/20 12:50 AM, Qinglang Miao wrote:
>> krealloc() may fail to expand the memory space.
> 
> Even with __GFP_NOFAIL?
> 
>    * ``GFP_KERNEL | __GFP_NOFAIL`` - overrides the default allocator behavior
>      and all allocation requests will loop endlessly until they succeed.
>      This might be really dangerous especially for larger orders.
> 
>> Add sanity checks to it,
>> and WARN() if that really happened.
> 
> As aside, there is no WARN added in this patch for a memory failure.
> 
>> Fixes: 771915c4f688 ("xfs: remove kmem_realloc()")
>> Reported-by: Hulk Robot <hulkci@huawei.com>
>> Signed-off-by: Qinglang Miao <miaoqinglang@huawei.com>
>> ---
>>   fs/xfs/xfs_mount.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
>> index 150ee5cb8..c07f48c32 100644
>> --- a/fs/xfs/xfs_mount.c
>> +++ b/fs/xfs/xfs_mount.c
>> @@ -80,9 +80,13 @@ xfs_uuid_mount(
>>   	}
>>   
>>   	if (hole < 0) {
>> -		xfs_uuid_table = krealloc(xfs_uuid_table,
>> +		uuid_t *if_xfs_uuid_table;
>> +		if_xfs_uuid_table = krealloc(xfs_uuid_table,
>>   			(xfs_uuid_table_size + 1) * sizeof(*xfs_uuid_table),
>>   			GFP_KERNEL | __GFP_NOFAIL);
>> +		if (!if_xfs_uuid_table)
>> +			goto out_duplicate;
> 
> And this would emit "Filesystem has duplicate UUID" which is not correct.
> 
> But anyway, the __GFP_NOFAIL in the call makes this all moot AFAICT.
> 
> -Eric
Hi Eric,

Sorry for neglecting __GFP_NOFAIL symbol, and I would add a WARN in 
memory failure next time.

Thanks for your advice！
> 
>> +		xfs_uuid_table = if_xfs_uuid_table;
>>   		hole = xfs_uuid_table_size++;
>>   	}
>>   	xfs_uuid_table[hole] = *uuid;
>>
> .
>