limit minixfs printks on corrupted dir i_size

This attempts to address CVE-2006-6058
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-6058

first reported at http://projects.info-pull.com/mokb/MOKB-17-11-2006.html

Essentially a corrupted minix dir inode reporting a very large
i_size will loop for a very long time in minix_readdir, minix_find_entry,
etc, because on EIO they just move on to try the next page.  This is
under the BKL, printk-storming as well.  This can lock up the machine
for a very long time.  Simply ratelimiting the printks gets things back
under control.  Make the message a bit more informative while we're here.
Signed-off-by: NEric Sandeen <sandeen@redhat.com>
Cc: Bodo Eggert <7eggert@gmx.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/minix/itree_v1.c

@@ -23,11 +23,16 @@ static inline block_t *i_data(struct inode *inode)
 static int block_to_path(struct inode * inode, long block, int offsets[DEPTH])
 {
 	int n = 0;
+	char b[BDEVNAME_SIZE];
 
 	if (block < 0) {
-		printk("minix_bmap: block<0\n");
+		printk("MINIX-fs: block_to_path: block %ld < 0 on dev %s\n",
+			block, bdevname(inode->i_sb->s_bdev, b));
 	} else if (block >= (minix_sb(inode->i_sb)->s_max_size/BLOCK_SIZE)) {
-		printk("minix_bmap: block>big\n");
+		if (printk_ratelimit())
+			printk("MINIX-fs: block_to_path: "
+			       "block %ld too big on dev %s\n",
+				block, bdevname(inode->i_sb->s_bdev, b));
 	} else if (block < 7) {
 		offsets[n++] = block;
 	} else if ((block -= 7) < 512) {

fs/minix/itree_v2.c

@@ -23,12 +23,17 @@ static inline block_t *i_data(struct inode *inode)
 static int block_to_path(struct inode * inode, long block, int offsets[DEPTH])
 {
 	int n = 0;
+	char b[BDEVNAME_SIZE];
 	struct super_block *sb = inode->i_sb;
 
 	if (block < 0) {
-		printk("minix_bmap: block<0\n");
+		printk("MINIX-fs: block_to_path: block %ld < 0 on dev %s\n",
+			block, bdevname(sb->s_bdev, b));
 	} else if (block >= (minix_sb(inode->i_sb)->s_max_size/sb->s_blocksize)) {
-		printk("minix_bmap: block>big\n");
+		if (printk_ratelimit())
+			printk("MINIX-fs: block_to_path: "
+			       "block %ld too big on dev %s\n",
+				block, bdevname(sb->s_bdev, b));
 	} else if (block < 7) {
 		offsets[n++] = block;
 	} else if ((block -= 7) < 256) {