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

[Benoît Thébaudeau]

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