From: Lubomir Rintel <lkundrak@v3.sk> 
Date: Wed, 2 Dec 2009 22:49:11 +0100 
Subject: [PATCH] Fix out-of bound writes 

Firstly, packed attribute is added to the structure so that extension 
is guarranteed to immediately follow name for the cross-name-extension 
reads to succeed. 
 
Secondly, writes into dir_entry->name that span through the extension as 
well are split into two, so that FORTIFY_SOURCE's bound checking does 
not abort dosfsck. There also was an off-by-one error in auto_rename()'s
sprintf().

diff -up dosfstools-3.0.6/src/check.c.bounds dosfstools-3.0.6/src/check.c
--- dosfstools-3.0.6/src/check.c.bounds	2009-10-04 09:15:58.000000000 +0200
+++ dosfstools-3.0.6/src/check.c	2009-12-06 12:32:42.922639364 +0100
@@ -131,7 +131,10 @@ loff_t alloc_rootdir_entry(DOS_FS *fs, D
 	}
 	memset(de,0,sizeof(DIR_ENT));
 	while (1) {
-	    sprintf(de->name,pattern,curr_num);
+	    char expanded[12];
+	    sprintf(expanded, pattern, curr_num);
+	    memcpy(de->name+4, expanded, 4);
+	    memcpy(de->ext, expanded+4, 3);
 	    clu_num = fs->root_cluster;
 	    i = 0;
 	    offset2 = cluster_start(fs,clu_num);
@@ -349,8 +352,11 @@ static void auto_rename(DOS_FILE *file)
     first = file->parent ? file->parent->first : root;
     number = 0;
     while (1) {
-	sprintf(file->dir_ent.name, "FSCK%04d", number / 1000);
-	sprintf(file->dir_ent.ext, "%03d", number % 1000);
+	char num[8];
+	sprintf(num, "%07d", number);
+	memcpy(file->dir_ent.name, "FSCK", 4);
+	memcpy(file->dir_ent.name+4, num, 4);
+	memcpy(file->dir_ent.ext, num+4, 3);
 	for (walk = first; walk; walk = walk->next)
 	    if (walk != file && !strncmp(walk->dir_ent.name,file->dir_ent.
 	      name,MSDOS_NAME)) break;
diff -up dosfstools-3.0.6/src/dosfsck.h.bounds dosfstools-3.0.6/src/dosfsck.h
--- dosfstools-3.0.6/src/dosfsck.h.bounds	2009-10-04 09:15:58.000000000 +0200
+++ dosfstools-3.0.6/src/dosfsck.h	2009-12-06 12:31:49.042643675 +0100
@@ -149,7 +149,7 @@ typedef struct {
     __u16	starthi;	/* High 16 bits of cluster in FAT32 */
     __u16	time,date,start;/* time, date and first cluster */
     __u32	size;		/* file size (in bytes) */
-} DIR_ENT;
+} __attribute__ ((packed)) DIR_ENT;
 
 typedef struct _dos_file {
     DIR_ENT dir_ent;
diff -up dosfstools-3.0.6/src/mkdosfs.c.bounds dosfstools-3.0.6/src/mkdosfs.c
--- dosfstools-3.0.6/src/mkdosfs.c.bounds	2009-10-04 09:15:58.000000000 +0200
+++ dosfstools-3.0.6/src/mkdosfs.c	2009-12-06 12:31:49.048645872 +0100
@@ -1254,7 +1254,8 @@ setup_tables (void)
   if ( memcmp(volume_name, "           ", 11) )
     {
       struct msdos_dir_entry *de = &root_dir[0];
-      memcpy(de->name, volume_name, 11);
+      memcpy(de->name, volume_name, 8);
+      memcpy(de->ext, volume_name+8, 3);
       de->attr = ATTR_VOLUME;
       ctime = localtime(&create_time);
       de->time = CT_LE_W((unsigned short)((ctime->tm_sec >> 1) +