[U-Boot] [PATCH v1] fat: fatwrite: fix the command for FAT12

[Philipp Skadorov]

Good morning,
I will update and test set_fatent_value as well and will send you patch v.2

Regards,
Philipp

> On Dec 11, 2016, at 10:05 AM, Benoît Thébaudeau <benoit.thebaudeau.dev at gmail.com> wrote:
> 
> Dear Stefan Brüns,
> 
> On Sun, Dec 11, 2016 at 12:29 AM, Stefan Bruens
> <stefan.bruens at rwth-aachen.de> wrote:
>> On Freitag, 9. Dezember 2016 13:55:37 CET Philipp Skadorov wrote:
>>> The u-boot command fatwrite empties FAT clusters from the beginning
>>> till the end of the file.
>>> Specifically for FAT12 it fails to detect the end of the file and goes
>>> beyond the file bounds thus corrupting the file system.
>>> 
>>> The users normally workaround this by re-formatting the partition as
>>> FAT16/FAT32, like here:
>>> https://github.com/FEDEVEL/openrex-uboot-v2015.10/issues/1
>>> 
>>> The patch is to check file bounds by already-existing macro that
>>> accounts for FAT12.
>>> The command then works correctly for all types of FAT.
>>> 
>>> Signed-off-by: Philipp Skadorov <philipp.skadorov at savoirfairelinux.com>
>>> Cc:Donggeun Kim <dg77.kim at samsung.com>
>>> ---
>>> fs/fat/fat_write.c | 5 +----
>>> 1 file changed, 1 insertion(+), 4 deletions(-)
>>> 
>>> diff --git a/fs/fat/fat_write.c b/fs/fat/fat_write.c
>>> index 40a3860..e4f600e 100644
>>> --- a/fs/fat/fat_write.c
>>> +++ b/fs/fat/fat_write.c
>>> @@ -670,16 +670,13 @@ static int clear_fatent(fsdata *mydata, __u32 entry)
>>> {
>>>      __u32 fat_val;
>>> 
>>> -     while (1) {
>>> +     while (!CHECK_CLUST(entry, mydata->fatsize)) {
>>>              fat_val = get_fatent_value(mydata, entry);
>>>              if (fat_val != 0)
>>>                      set_fatent_value(mydata, entry, 0);
>>>              else
>>>                      break;
>>> 
>>> -             if (fat_val == 0xfffffff || fat_val == 0xffff)
>>> -                     break;
>>> -
>>>              entry = fat_val;
>>>      }
>> 
>> NAK.
>> 
>> This corrupts the file system, as set_fatent_value(...) has:
>> 
>>        switch (mydata->fatsize) {
>>        case 32:
>>                bufnum = entry / FAT32BUFSIZE;
>>                offset = entry - bufnum * FAT32BUFSIZE;
>>                break;
>>        case 16:
>>                bufnum = entry / FAT16BUFSIZE;
>>                offset = entry - bufnum * FAT16BUFSIZE;
>>                break;
>>        default:
>>                /* Unsupported FAT size */
>>                return -1;
>>        }
> 
> So this patch can be kept, but it needs to be combined with a new one
> in a series to fully fix fatwrite for FAT12.
> 
> Best regards,
> Benoît