Hi Anatolij,
On 05/12/2012 08:41 AM, Anatolij Gustschin wrote:
Hello,
On Wed, 02 May 2012 19:17:41 -0700 Aaron Williams Aaron.Williams@cavium.com wrote:
This patch fixes several issues where sector offsets can overflow due to being limited to 16-bits. There are many cases which can cause an overflow, including large FAT32 partitions and partitions that start at a sufficiently large offset on the storage device.
For large FAT32 partitions only changing of fatlength, rootdir_sect and data_begin is needed to avoid overflows. Changing of fat_sect shouldn't be needed.
What do you mean exactly by "partitions starting at a sufficiently large offset on the storage device"? How do you create such partition? I've tested with a 210 GB FAT32 partition as the fourth primary partition on a 2 TB disk. This partition is the last partition on the disk, so its offset is sufficiently large. For this test only fatlength, rootdir_sect and data_begin was changed to __u32 and int and I do not see issues when listing or loading the files from this partition.
You are correct about fat_sect, I misread the code and changed that one as well. I don't think it really matters since another changing it back to a __u16 won't save any space in the data structure on most platforms.
It looks like the corruption problems I was seeing were due to the fact that the file I was reading was after a number of very large files in a 64GB FAT32 partition and I ran into overflows. The partition location shouldn't have any impact unless we're talking about 2+TB drives, in which case I expect there will be numerous other things that will break.
Numerous issues were observed and fixed when a 64GB FAT32 filesystem was accessed due to truncation.
Signed-off-by: Aaron Williams aaron.williams@caviumnetworks.com
include/fat.h | 10 +++++----- 1 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/include/fat.h b/include/fat.h index 4c92442..7215628 100644 --- a/include/fat.h +++ b/include/fat.h @@ -178,12 +178,12 @@ typedef struct dir_slot { typedef struct { __u8 *fatbuf; /* Current FAT buffer */ int fatsize; /* Size of FAT in bits */
__u16 fatlength; /* Length of FAT in sectors */__u16 fat_sect; /* Starting sector of the FAT */__u16 rootdir_sect; /* Start sector of root directory */__u16 sect_size; /* Size of sectors in bytes */
__u32 fat_sect; /* Starting sector of the FAT */__u32 rootdir_sect; /* Start sector of root directory */__u32 fatlength; /* Length of FAT in sectors */ __u16 clust_size; /* Size of clusters in sectors */
short data_begin; /* The sector of the first cluster, can be negative */
__u16 sect_size; /* Size of sectors in bytes */int data_begin; /* The sector of the first cluster, can be negative */ int fatbufnum; /* Used by get_fatent, init to -1 */} fsdata;
The patch is probably corrupted by your mailer, it doesn't apply.
Thanks, Anatolij
Unfortunately our outbound Exchange mail server tends to "fix" mail formatting making patch submission rather difficult. I'll see what I can do to try and bypass it.
-Aaron