linux-kernel - Re: [PATCH] of: overlay: fix null pointer dereferencing in find_dup_cset_node_entry() and find_dup_cset

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Date:   Sun, 11 Dec 2022 10:14:47 +0800
From:   Ruan Jinjie <ruanjinjie@...wei.com>
To:     Rob Herring <robh@...nel.org>
CC:     <frowand.list@...il.com>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] of: overlay: fix null pointer dereferencing in
 find_dup_cset_node_entry() and find_dup_cset_prop()



On 2022/12/10 4:59, Rob Herring wrote:
> On Tue, Dec 06, 2022 at 04:36:57PM +0800, ruanjinjie wrote:
>> when kmalloc() fail to allocate memory in kasprintf(), fn_1 or fn_2 will
>> be NULL, strcmp() will cause null pointer dereference.
>>
>> Fixes: 2fe0e8769df9 ("of: overlay: check prevents multiple fragments touching same property")
>> Signed-off-by: ruanjinjie <ruanjinjie@...wei.com>
>> ---
>>  drivers/of/overlay.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
>> index bd8ff4df723d..49c066b51148 100644
>> --- a/drivers/of/overlay.c
>> +++ b/drivers/of/overlay.c
>> @@ -545,6 +545,11 @@ static int find_dup_cset_node_entry(struct overlay_changeset *ovcs,
>>  
>>  		fn_1 = kasprintf(GFP_KERNEL, "%pOF", ce_1->np);
>>  		fn_2 = kasprintf(GFP_KERNEL, "%pOF", ce_2->np);
>> +		if (!fn_1 || !fn_2) {
>> +			kfree(fn_1);
>> +			kfree(fn_2);
>> +			return -ENOMEM;
>> +		}
>>  		node_path_match = !strcmp(fn_1, fn_2);
> 
> We don't actually care what the return code is, so just change this to:
> 
> node_path_match = !fn_1 || !fn_2 || !strcmp(fn_1, fn_2);
Thank you very much!I'll give the v2 patch soon.
> 
>>  		kfree(fn_1);
>>  		kfree(fn_2);
>> @@ -580,6 +585,11 @@ static int find_dup_cset_prop(struct overlay_changeset *ovcs,
>>  
>>  		fn_1 = kasprintf(GFP_KERNEL, "%pOF", ce_1->np);
>>  		fn_2 = kasprintf(GFP_KERNEL, "%pOF", ce_2->np);
>> +		if (!fn_1 || !fn_2) {
>> +			kfree(fn_1);
>> +			kfree(fn_2);
>> +			return -ENOMEM;
>> +		}
>>  		node_path_match = !strcmp(fn_1, fn_2);
>>  		kfree(fn_1);
>>  		kfree(fn_2);
>> -- 
>> 2.25.1
>>
>>
>