[Bug 271312] inum > maxino should probably be inum >= maxino in fsck_ffs

From: <bugzilla-noreply_at_freebsd.org>
Date: Mon, 08 May 2023 09:45:10 UTC

            Bug ID: 271312
           Summary: inum > maxino should probably be inum >= maxino in
           Product: Base System
           Version: CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: bin
          Assignee: bugs@FreeBSD.org
          Reporter: rtm@lcs.mit.edu

Created attachment 242053
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=242053&action=edit
broken file system image that causes fsck to crash due to off-by-one maxino

fsck_ffs has some checks for an out-of-range i-number that say "... >
maxino" which I think should be >=.

One consequence is that inoinfo() in fsutil.c can index beyond the end
of inostathead[]:

        if (inum > maxino)
                errx(EEXIT, "inoinfo: inumber %ju out of range",
        ilp = &inostathead[inum / sblock.fs_ipg];

A backtrace from fsck_ffs -y on the attached file-system image:

Program received signal SIGBUS, Bus error.
Object-specific hardware error.
0x000000000021f051 in pass2check (idesc=0x7fffffffe7b8) at pass2.c:486
486                     switch (inoinfo(dirp->d_ino)->ino_state) {
(gdb) where
#0  0x000000000021f051 in pass2check (idesc=0x7fffffffe7b8) at pass2.c:486
#1  0x00000000002093e7 in dirscan (idesc=0x7fffffffe7b8) at dir.c:211
#2  0x000000000021318b in ckinode (dp=0x7fffffffe6b8, idesc=0x7fffffffe7b8)
    at inode.c:126
#3  0x000000000021e130 in pass2 () at pass2.c:202
#4  0x0000000000219a7d in checkfilesys (filesys=0x7fffffffed79 "junk")
    at main.c:468
#5  0x0000000000218f42 in main (argc=1, argv=0x7fffffffea28) at main.c:210

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