Quoting from the email thrown around between kirk, bde and iedowse@..

<QUOTE>
Overflow of cg_niblk causes spurious "SUMMARY INFORMATION BAD" warnings
prompts in fsck_ffs.  cg_niblk has type int16_t, but it is (ab)used
to hold the number of inodes per group (it has nothing to do with the
number of inode blocks in the cg as claimed in ffs/fs.h), and there
can be lots of inodes per group.  E.g.,

    newfs -i 8192 -b 16384 -f 16384 -c 255 ...

gives 0xA900 inodes/group.  Assignment of this to cg_niblk gives
-0x5700.  This is mostly harmless (ufs/ffs doesn't use cg_niblk, and
bug-for-bug compatible overflow occurs in newfs), but in
fsck_ffs/pass5.c, negative values of cg_niblk limit cg_irotor to 0
and the summary info appears to be bad.
</QUOTE>

Submitted by:	Bruce Evans <bde@zeta.org.au>
Obtained from:	Kirk McKusick <mckusick@mckusick.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/sbin/fsck_ifs/pass5.c b/sbin/fsck_ifs/pass5.c
index e395625..a9f4487 100644
--- a/sbin/fsck_ifs/pass5.c
+++ b/sbin/fsck_ifs/pass5.c
@@ -68,6 +68,10 @@ pass5()
 
 	inoinfo(WINO)->ino_state = USTATE;
 	memset(newcg, 0, (size_t)fs->fs_cgsize);
+	/*
+	 * Note: cg_niblk is 16 bits and may overflow, so it must never
+	 * be used except for comparing with the old value.
+	 */
 	newcg->cg_niblk = fs->fs_ipg;
 	if (cvtlevel >= 3) {
 		if (fs->fs_maxcontig < 2 && fs->fs_contigsumsize > 0) {
@@ -197,7 +201,7 @@ pass5()
 			newcg->cg_frotor = cg->cg_frotor;
 		else
 			newcg->cg_frotor = 0;
-		if (cg->cg_irotor < newcg->cg_niblk)
+		if (cg->cg_irotor < fs->fs_ipg)
 			newcg->cg_irotor = cg->cg_irotor;
 		else
 			newcg->cg_irotor = 0;