The FAT is read/flushed in segments of 6 (FATBUFBLOCKS) disk sectors. The last segment may be less than 6 sectors, cap the length.

Signed-off-by: Stefan Brüns stefan.bruens@rwth-aachen.de Reviewed-by: Benoît Thébaudeau benoit.thebaudeau.dev@gmail.com --- fs/fat/fat.c | 1 + fs/fat/fat_write.c | 22 ++++++++++++---------- 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/fs/fat/fat.c b/fs/fat/fat.c index df9f2b5656..6319581406 100644 --- a/fs/fat/fat.c +++ b/fs/fat/fat.c @@ -202,6 +202,7 @@ static __u32 get_fatent(fsdata *mydata, __u32 entry) __u32 fatlength = mydata->fatlength; __u32 startblock = bufnum * FATBUFBLOCKS;

+ /* Cap length if fatlength is not a multiple of FATBUFBLOCKS */ if (startblock + getsize > fatlength) getsize = fatlength - startblock;

diff --git a/fs/fat/fat_write.c b/fs/fat/fat_write.c index 40a3860e47..0be60ecd99 100644 --- a/fs/fat/fat_write.c +++ b/fs/fat/fat_write.c @@ -117,10 +117,11 @@ static int flush_dirty_fat_buffer(fsdata *mydata) if ((!mydata->fat_dirty) || (mydata->fatbufnum == -1)) return 0;

- startblock += mydata->fat_sect; + /* Cap length if fatlength is not a multiple of FATBUFBLOCKS */ + if (startblock + getsize > fatlength) + getsize = fatlength - startblock;

- if (getsize > fatlength) - getsize = fatlength; + startblock += mydata->fat_sect;

/* Write FAT buf */ if (disk_write(startblock, getsize, bufptr) < 0) { @@ -187,8 +188,9 @@ static __u32 get_fatent_value(fsdata *mydata, __u32 entry) __u32 fatlength = mydata->fatlength; __u32 startblock = bufnum * FATBUFBLOCKS;

- if (getsize > fatlength) - getsize = fatlength; + /* Cap length if fatlength is not a multiple of FATBUFBLOCKS */ + if (startblock + getsize > fatlength) + getsize = fatlength - startblock;

startblock += mydata->fat_sect; /* Offset from start of disk */

@@ -494,15 +496,15 @@ static int set_fatent_value(fsdata *mydata, __u32 entry, __u32 entry_value) __u32 fatlength = mydata->fatlength; __u32 startblock = bufnum * FATBUFBLOCKS;

- fatlength *= mydata->sect_size; - startblock += mydata->fat_sect; - - if (getsize > fatlength) - getsize = fatlength; + /* Cap length if fatlength is not a multiple of FATBUFBLOCKS */ + if (startblock + getsize > fatlength) + getsize = fatlength - startblock;

if (flush_dirty_fat_buffer(mydata) < 0) return -1;

+ startblock += mydata->fat_sect; + if (disk_read(startblock, getsize, bufptr) < 0) { debug("Error reading FAT blocks\n"); return -1;