[U-Boot] [PATCH] cmd: nvedit: env_get_f must check for env_get_char error codes

[Simon Goldschmidt]

On 01.02.2018 00:00, York Sun wrote:
> On 01/30/2018 10:57 PM, Simon Goldschmidt wrote:
>> env_get_f calls env_get_char to load single characters from the
>> environment. However, the return value of env_get_char was not
>> checked for errors. Now if the env driver does not support the
>> .get_char call, env_get_f did not notice this and looped over the
>> whole size of the environment, calling env_get_char over 8000
>> times with the default settings, just to return an error in the
>> end.
>>
>> Fix this by checking if env_get_char returns < 0.
>>
>> Signed-off-by: Simon Goldschmidt <sgoldschmidt at de.pepperl-fuchs.com>
>> ---
>>
>>   cmd/nvedit.c | 11 ++++++++---
>>   1 file changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/cmd/nvedit.c b/cmd/nvedit.c
>> index a690d743cd..4cb25b8248 100644
>> --- a/cmd/nvedit.c
>> +++ b/cmd/nvedit.c
>> @@ -650,12 +650,14 @@ char *env_get(const char *name)
>>    */
>>   int env_get_f(const char *name, char *buf, unsigned len)
>>   {
>> -	int i, nxt;
>> +	int i, nxt, c;
>>   
>>   	for (i = 0; env_get_char(i) != '\0'; i = nxt + 1) {
>>   		int val, n;
>>   
>> -		for (nxt = i; env_get_char(nxt) != '\0'; ++nxt) {
>> +		for (nxt = i; (c = env_get_char(nxt)) != '\0'; ++nxt) {
>> +			if (c < 0)
>> +				return c;
>>   			if (nxt >= CONFIG_ENV_SIZE)
>>   				return -1;
>>   		}
>> @@ -666,7 +668,10 @@ int env_get_f(const char *name, char *buf, unsigned len)
>>   
>>   		/* found; copy out */
>>   		for (n = 0; n < len; ++n, ++buf) {
>> -			*buf = env_get_char(val++);
>> +			c = env_get_char(val++);
>> +			if (c < 0)
>> +				return c;
>> +			*buf = c;
>>   			if (*buf == '\0')
>>   				return n;
>>   		}
>>
> Simon,
>
> This patch looks correct. But it doesn't fix NOR flash. Do you have plan
> to add .get_char function to other drivers? Without that function, we
> cannot get env variables before relocation.

Ehrm, sorry  I don't plan to do that, no: my target seems to run fine 
without this.

Given that only the eeprom and nvram env drivers support the get_char 
method, I don't know if this is widely used at all. Maybe a better 
fallback would be to just remove that get_char code path totally and 
always load from the internal (default) environment until the full 
environment is available (after relocation).

After all, the environment variables loaded via get_char are not CRC 
checked at all. To me, this is another indication that this code is not 
really useful and should probably be removed.

Maxime and others, what do you think?

Simon