From 6c1a808052ba6a875df7aa450b6df4b199f3a281 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Stefan=20Br=C3=BCns?= Date: Sat, 17 Dec 2016 00:27:50 +0100 Subject: [PATCH] fs/fat: Avoid corruption of sectors following the FAT MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Benoît Thébaudeau --- 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 aab0b0e71d..4605020854 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 */ @@ -499,15 +501,15 @@ 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; -- 2.25.1