fs: fat: fix reading non-cluster-aligned root directory

[oweals/u-boot.git] / fs / fat / fat.c

diff --git a/fs/fat/fat.c b/fs/fat/fat.c
index 6ade4ea54ecd8e227196c13c73e077863801828a..c5997c21735f9714aae7c63486750837cac87688 100644 (file)
--- a/fs/fat/fat.c
+++ b/fs/fat/fat.c
@@ -602,8 +602,13 @@ static int get_fs_info(fsdata *mydata)
                mydata->data_begin = mydata->rootdir_sect +
                                        mydata->rootdir_size -
                                        (mydata->clust_size * 2);
-               mydata->root_cluster =
-                       sect_to_clust(mydata, mydata->rootdir_sect);
+
+               /*
+                * The root directory is not cluster-aligned and may be on a
+                * "negative" cluster, this will be handled specially in
+                * next_cluster().
+                */
+               mydata->root_cluster = 0;
        }
 
        mydata->fatbufnum = -1;
@@ -733,20 +738,38 @@ static void fat_itr_child(fat_itr *itr, fat_itr *parent)
        itr->last_cluster = 0;
 }
 
-static void *next_cluster(fat_itr *itr)
+static void *next_cluster(fat_itr *itr, unsigned *nbytes)
 {
        fsdata *mydata = itr->fsdata;  /* for silly macros */
        int ret;
        u32 sect;
+       u32 read_size;
 
        /* have we reached the end? */
        if (itr->last_cluster)
                return NULL;
 
-       sect = clust_to_sect(itr->fsdata, itr->next_clust);
+       if (itr->is_root && itr->fsdata->fatsize != 32) {
+               /*
+                * The root directory is located before the data area and
+                * cannot be indexed using the regular unsigned cluster
+                * numbers (it may start at a "negative" cluster or not at a
+                * cluster boundary at all), so consider itr->next_clust to be
+                * a offset in cluster-sized units from the start of rootdir.
+                */
+               unsigned sect_offset = itr->next_clust * itr->fsdata->clust_size;
+               unsigned remaining_sects = itr->fsdata->rootdir_size - sect_offset;
+               sect = itr->fsdata->rootdir_sect + sect_offset;
+               /* do not read past the end of rootdir */
+               read_size = min_t(u32, itr->fsdata->clust_size,
+                                 remaining_sects);
+       } else {
+               sect = clust_to_sect(itr->fsdata, itr->next_clust);
+               read_size = itr->fsdata->clust_size;
+       }
 
-       debug("FAT read(sect=%d), clust_size=%d, DIRENTSPERBLOCK=%zd\n",
-             sect, itr->fsdata->clust_size, DIRENTSPERBLOCK);
+       debug("FAT read(sect=%d), clust_size=%d, read_size=%u, DIRENTSPERBLOCK=%zd\n",
+             sect, itr->fsdata->clust_size, read_size, DIRENTSPERBLOCK);
 
        /*
         * NOTE: do_fat_read_at() had complicated logic to deal w/
@@ -757,18 +780,17 @@ static void *next_cluster(fat_itr *itr)
         * dent at a time and iteratively constructing the vfat long
         * name.
         */
-       ret = disk_read(sect, itr->fsdata->clust_size,
-                       itr->block);
+       ret = disk_read(sect, read_size, itr->block);
        if (ret < 0) {
                debug("Error: reading block\n");
                return NULL;
        }
 
+       *nbytes = read_size * itr->fsdata->sect_size;
        itr->clust = itr->next_clust;
        if (itr->is_root && itr->fsdata->fatsize != 32) {
                itr->next_clust++;
-               sect = clust_to_sect(itr->fsdata, itr->next_clust);
-               if (sect - itr->fsdata->rootdir_sect >=
+               if (itr->next_clust * itr->fsdata->clust_size >=
                    itr->fsdata->rootdir_size) {
                        debug("nextclust: 0x%x\n", itr->next_clust);
                        itr->last_cluster = 1;
@@ -787,9 +809,8 @@ static void *next_cluster(fat_itr *itr)
 static dir_entry *next_dent(fat_itr *itr)
 {
        if (itr->remaining == 0) {
-               struct dir_entry *dent = next_cluster(itr);
-               unsigned nbytes = itr->fsdata->sect_size *
-                       itr->fsdata->clust_size;
+               unsigned nbytes;
+               struct dir_entry *dent = next_cluster(itr, &nbytes);
 
                /* have we reached the last cluster? */
                if (!dent) {