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Index:	etc/ncheck.c 4.3BSD Fix

Description:
	bmap() only pretends to handle one indirect block, which is
	enough in practise.  However, a typo caused it to not to work
	at all for indirect blocks, leading to core dumps.  Instead
	of reading the indirect block, it read block i-NDADDR and
	grabbed bogus block numbers out of it.

Repeat-By:
	Well, this was awhile ago, but if on a 4k filesys you have a
	directory longer than 13*4096 == 53248, ncheck will blow up.

Fix:
The first way is to fix the typo, resulting in the same code as in dcheck.c:

383c383
< 	bread(fsbtodb(&sblock, gip->di_ib[i]), (char *)ibuf, sizeof(ibuf));
---
> 	bread(fsbtodb(&sblock, gip->di_ib[0]), (char *)ibuf, sizeof(ibuf));

The second way, which is mostly a waste of time but I actually tested
it, is to fix it "right" by lifting and hacking the indirect code from
the standalone sys.c.  Here it is in case someone has directories larger
than, lessee, is it some 4 million chars on a 4k fs?  Anyway, big.

*** /tmp/,RCSt1028034	Tue Oct 21 01:47:26 1986
--- /tmp/,RCSt2028034	Tue Oct 21 01:47:27 1986
***************
*** 369,385 ****
  
  daddr_t
! bmap(i)
! 	int i;
  {
! 	daddr_t ibuf[MAXNINDIR];
  
! 	if(i < NDADDR)
! 		return(gip->di_db[i]);
! 	i -= NDADDR;
! 	if(i > NINDIR(&sblock)) {
! 		fprintf(stderr, "ncheck: %u - huge directory\n", ino);
! 		return((daddr_t)0);
  	}
! 	bread(fsbtodb(&sblock, gip->di_ib[i]), (char *)ibuf, sizeof(ibuf));
! 	return(ibuf[i]);
  }
--- 369,440 ----
  
+ /*
+  * Swiped from standalone sys.c.
+  */
+ #define	NBUFS	4
+ char	b[NBUFS][MAXBSIZE];
+ daddr_t	blknos[NBUFS];
+ 
  daddr_t
! bmap(bn)
! 	register daddr_t bn;
  {
! 	register int j;
! 	int i, sh;
! 	daddr_t nb, *bap;
  
! 	if (bn < 0) {
! 		fprintf(stderr, "ncheck: bn %d negative\n", bn);
! 		return ((daddr_t)0);
  	}
! 
! 	/*
! 	 * blocks 0..NDADDR are direct blocks
! 	 */
! 	if(bn < NDADDR)
! 		return(gip->di_db[bn]);
! 
! 	/*
! 	 * addresses NIADDR have single and double indirect blocks.
! 	 * the first step is to determine how many levels of indirection.
! 	 */
! 	sh = 1;
! 	bn -= NDADDR;
! 	for (j = NIADDR; j > 0; j--) {
! 		sh *= NINDIR(&sblock);
! 		if (bn < sh)
! 			break;
! 		bn -= sh;
! 	}
! 	if (j == 0) {
! 		printf("ncheck: bn %ld ovf, ino %u\n", bn, ino);
! 		return ((daddr_t)0);
! 	}
! 
! 	/*
! 	 * fetch the first indirect block address from the inode
! 	 */
! 	nb = gip->di_ib[NIADDR - j];
! 	if (nb == 0) {
! 		printf("ncheck: bn %ld void1, ino %u\n", bn, ino);
! 		return ((daddr_t)0);
! 	}
! 
! 	/*
! 	 * fetch through the indirect blocks
! 	 */
! 	for (; j <= NIADDR; j++) {
! 		if (blknos[j] != nb) {
! 			bread(fsbtodb(&sblock, nb), b[j], sblock.fs_bsize);
! 			blknos[j] = nb;
! 		}
! 		bap = (daddr_t *)b[j];
! 		sh /= NINDIR(&sblock);
! 		i = (bn / sh) % NINDIR(&sblock);
! 		nb = bap[i];
! 		if(nb == 0) {
! 			printf("ncheck: bn %ld void2, ino %u\n", bn, ino);
! 			return ((daddr_t)0);
! 		}
! 	}
! 	return (nb);
  }