[Bug 257557] Garbage on disk (or USB memory stick) can cause GEOM taste ffs_sbget() to crash.

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=257557

            Bug ID: 257557
           Summary: Garbage on disk (or USB memory stick) can cause GEOM
                    taste ffs_sbget() to crash.
           Product: Base System
           Version: 13.0-RELEASE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: kern
          Assignee: bugs@FreeBSD.org
          Reporter: rtm@lcs.mit.edu

Created attachment 226873
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=226873&action=edit
A usb key image that causes a kernel page fault.

A USB memory stick with the attached content, if inserted
in my 13.0-RELEASE-p3 amd64 machine, causes a crash. Here's a
kernel backtrace:

panic: vm_fault_lookup: fault on nofault entry, addr: 0xfffffe0009409000
cpuid = 0
time = 1627895621
KDB: stack backtrace:
#0 0xffffffff80c57515 at kdb_backtrace+0x65
#1 0xffffffff80c09ef1 at vpanic+0x181
#2 0xffffffff80c09d63 at panic+0x43
#3 0xffffffff80f289ab at vm_fault+0x144b
#4 0xffffffff80f27481 at vm_fault_trap+0xb1
#5 0xffffffff8108b3b8 at trap_pfault+0x1f8
#6 0xffffffff8108a86d at trap+0x27d
#7 0xffffffff81061978 at calltrap+0x8
#8 0xffffffff80efc974 at ffs_sbget+0x3c4
#9 0xffffffff80b54a77 at g_label_ufs_taste_common+0x57
#10 0xffffffff80b533af at g_label_taste+0x1df
#11 0xffffffff80b51aba at g_new_provider_event+0x7a
#12 0xffffffff80b4cc3e at g_run_events+0x12e
#13 0xffffffff80bc7e2e at fork_exit+0x7e
#14 0xffffffff810629fe at fork_trampoline+0xe

You can also get the crash with

  % sudo mdconfig -f fat12.img

fat12.img contains garbage that apparently looks enough
like an FFS file system that GEOM taste's call to ffs_sbget()
proceeds, but then crashes near the end.

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