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dosfs: Fix file extend

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Only append a valid cluster chain (cluster added > 0), otherwise we
overwrite the root directory cluster (cluster 0) of a FAT12 or FAT16
with arbitrary data.
This commit is contained in:
Sebastian Huber
2013-02-15 17:01:55 +01:00
parent 0c9b35e8dd
commit df8c2d77f6
1 changed files with 24 additions and 23 deletions
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cpukit/libfs/src/dosfs/fat_file.c
+24 -23
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@@ -637,42 +637,43 @@ fat_file_extend(
new_length -= (cls2add - cls_added) << fs_info->vol.bpc_log2;
}
/* add new chain to the end of existed */
if ( fat_fd->fat_file_size == 0 )
if (cls_added > 0)
{
fat_fd->map.disk_cln = fat_fd->cln = chain;
fat_fd->map.file_cln = 0;
}
else
{
if (fat_fd->map.last_cln != FAT_UNDEFINED_VALUE)
/* add new chain to the end of existing */
if ( fat_fd->fat_file_size == 0 )
{
old_last_cl = fat_fd->map.last_cln;
fat_fd->map.disk_cln = fat_fd->cln = chain;
fat_fd->map.file_cln = 0;
}
else
{
rc = fat_file_ioctl(fs_info, fat_fd, F_CLU_NUM,
(fat_fd->fat_file_size - 1), &old_last_cl);
if (fat_fd->map.last_cln != FAT_UNDEFINED_VALUE)
{
old_last_cl = fat_fd->map.last_cln;
}
else
{
rc = fat_file_ioctl(fs_info, fat_fd, F_CLU_NUM,
(fat_fd->fat_file_size - 1), &old_last_cl);
if ( rc != RC_OK )
{
fat_free_fat_clusters_chain(fs_info, chain);
return rc;
}
}
rc = fat_set_fat_cluster(fs_info, old_last_cl, chain);
if ( rc != RC_OK )
{
fat_free_fat_clusters_chain(fs_info, chain);
return rc;
}
fat_buf_release(fs_info);
}
rc = fat_set_fat_cluster(fs_info, old_last_cl, chain);
if ( rc != RC_OK )
{
fat_free_fat_clusters_chain(fs_info, chain);
return rc;
}
fat_buf_release(fs_info);
}
/* update number of the last cluster of the file if it changed */
if (cls_added != 0)
{
/* update number of the last cluster of the file */
fat_fd->map.last_cln = last_cl;
if (fat_fd->fat_file_type == FAT_DIRECTORY)
{
rc = fat_init_clusters_chain(fs_info, chain);