[Bug 244350] [6] [Kernel panic: getblk: size(75776) > maxbcachebuf(65536)] observed while mouting the UFS USB drive on FreeBSD13-CURRENT, FreeBSD 12.1-RELEASE r354233 and FreeBSD 12.1-STABLE r358121

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=244350

            Bug ID: 244350
           Summary: [6] [Kernel panic: getblk: size(75776) >
                    maxbcachebuf(65536)] observed while mouting the UFS
                    USB drive on FreeBSD13-CURRENT, FreeBSD 12.1-RELEASE
                    r354233 and FreeBSD 12.1-STABLE r358121
           Product: Base System
           Version: CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: bugs at FreeBSD.org
          Reporter: neerajpal09 at gmail.com

Created attachment 211872
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=211872&action=edit
Contains PoC UFS image and detailed logs includes 13-current, 12.1-release and
12.1-stable

Hi there,

Kernel Panic is observed while mounting the usb drive which contains malicious
UFS filesystem image.

But if the automount is configured or user has ability to mount the usb drive
then during mount kernel panic occurs.

No user authentication and interaction is needed in case of automount is
configured, tested with "/etc/fstab".

Just flash the attached UFS image to usb drive and plug the usb drive to
FreeBSD 13-CURRENT, 12.1-RELEASE, or 12.1-STABLE, then mount it.

[Kernel Log - FreeBSD 13-CURRENT]

freebsd dumped core - see /var/crash/vmcore.3

Wed Feb 19 18:42:20 UTC 2020

FreeBSD freebsd 13.0-CURRENT FreeBSD 13.0-CURRENT #0: Wed Feb 19
01:58:08 UTC 2020
root at freebsd:/usr/obj/usr/src/amd64.amd64/sys/GENERIC  amd64

panic: getblk: size(75776) > maxbcachebuf(65536)

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This GDB was configured as "amd64-marcel-freebsd"...

Unread portion of the kernel message buffer:
panic: getblk: size(75776) > maxbcachebuf(65536)

cpuid = 2
time = 1582135933
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe0039ea3320
vpanic() at vpanic+0x185/frame 0xfffffe0039ea3380
panic() at panic+0x43/frame 0xfffffe0039ea33e0
getblkx() at getblkx+0x807/frame 0xfffffe0039ea34b0
breadn_flags() at breadn_flags+0x44/frame 0xfffffe0039ea3520
ffs_use_bread() at ffs_use_bread+0x70/frame 0xfffffe0039ea3590
ffs_sbget() at ffs_sbget+0x24f/frame 0xfffffe0039ea3600
ffs_mount() at ffs_mount+0xdf3/frame 0xfffffe0039ea37b0
vfs_domount() at vfs_domount+0x83c/frame 0xfffffe0039ea39e0
vfs_donmount() at vfs_donmount+0x911/frame 0xfffffe0039ea3a80
sys_nmount() at sys_nmount+0x69/frame 0xfffffe0039ea3ac0
amd64_syscall() at amd64_syscall+0x168/frame 0xfffffe0039ea3bf0
fast_syscall_common() at fast_syscall_common+0x101/frame 0xfffffe0039ea3bf0
--- syscall (378, FreeBSD ELF64, sys_nmount), rip = 0x8002f7a1a, rsp =
0x7fffffffd3b8, rbp = 0x7fffffffd920 ---
KDB: enter: panic
Uptime: 39m54s
Dumping 258 out of 4062 MB:..7%..13%..25%..31%..44%..56%..62%..75%..81%..93%


[Attachments]
+ UFS filesystem image
+ detailed logs from FreeBSD 13-CURRENT, 12.1-RELEASE, and 12.1-STABLE.

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