On 05/17/18 09:56, Frank Rowand wrote:
> Hi Rob,
> 
> On 05/16/18 21:19, frowand.l...@gmail.com wrote:
>> From: Frank Rowand <frank.row...@sony.com>
>>
>> The smatch static checker marks the data in offset as untrusted,
>> leading it to warn:
>>
>>   drivers/of/resolver.c:125 update_usages_of_a_phandle_reference()
>>   error: buffer underflow 'prop->value' 's32min-s32max'
>>
>> Add check to verify that offset is within the property data.
>>
>> Reported-by: Dan Carpenter <dan.carpen...@oracle.com>
>> Signed-off-by: Frank Rowand <frank.row...@sony.com>
>> ---
>>  drivers/of/resolver.c | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/of/resolver.c b/drivers/of/resolver.c
>> index 65d0b7adfcd4..7edfac6f1914 100644
>> --- a/drivers/of/resolver.c
>> +++ b/drivers/of/resolver.c
>> @@ -122,6 +122,11 @@ static int update_usages_of_a_phandle_reference(struct 
>> device_node *overlay,
>>                      goto err_fail;
>>              }
>>  
>> +            if (offset < 0 || offset + sizeof(__be32) > prop->length) {
>> +                    err = -EINVAL;
>> +                    goto err_fail;
>> +            }
>> +
>>              *(__be32 *)(prop->value + offset) = cpu_to_be32(phandle);
>>      }
>>  
>>
> 
> I should have mentioned that this results in a new compile warning
> for W=2 and W=3.  The new if statement results in:
> 

W=2 warning is:

> drivers/of/resolver.c:125:45: warning: comparison between signed and unsigned 
> integer expressions [-Wsign-compare]

W=3 warning is:

drivers/of/resolver.c:125:3: warning: conversion to 'unsigned int' from 'int' 
may change the sign of the result [-Wsign-conversion]

> 
> There are other pre-existing warnings in the same file for comparing
> an integer to prop->length.  The correct solution is probably to
> change the type of the length field in struct property to be
> unsigned.  I have added that task to my todo list.
> 
> -Frank
> 

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