Re: Panic on attempt to kern_stat / mount bad fs

On Apr 27, 2008, at 5:52 PM, Garrett Cooper wrote:

> Trying to use more of my harddisk, I formatted 2 labels I previously  
> fdisked on my machine (note that there wasn't a modification in MBRs  
> or slices, just partitions).
>
> Later on, I was recompiling my kernel and world recently and my  
> machine took a nose dive (panicked) partway through. The machine  
> rebooted by itself (to my surprise) and subsequently panicked again  
> attempting to mount one of the newly formatted filesystems.
>
> I quickly logged in locally, removed the 1/2 filesystems from my  
> fstab automount list and rebooted yet again. After that, and once I  
> removed background_fsck_enable=YES from rc.conf, everything appears  
> to be smooth sailing (knock on wood).
>
> I have 2 vmcore's that I can debug with: one from the first panic  
> and another from the 2nd panic.
>
> (I had to rebuild the kernel after I removed apcupsd as I have a USB  
> kbd and apcupsd provides uhid -- well, sort of...).
>
> optimus# uname -a
> FreeBSD optimus 8.0-CURRENT FreeBSD 8.0-CURRENT #14: Sun Apr 27  
> 17:09:22 PDT 2008     root_at_optimus:/usr/obj/usr/src/sys/OPTIMUS  i386
>
> I'll provide more info when requested.
>
> Thanks,
> -Garrett

Looks like there might be some missing error checking logic in the fs  
area:

optimus# kgdb -c /var/crash/vmcore.0 /boot/kernel.old/kernel
kgdb: kvm_nlist(_stopped_cpus):
kgdb: kvm_nlist(_stoppcbs):
[GDB will not be able to debug user-mode threads: /usr/lib/ 
libthread_db.so: Undefined symbol "ps_pglobal_lookup"]
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Unread portion of the kernel message buffer:
panic: ufs_dirbad: /scratch: bad dir ino 2 at offset 0: mangled entry
Uptime: 9d16h44m22s
Physical memory: 2038 MB
Dumping 250 MB: 235 219 203 187 171 155 139 123 107 91 75 59 43 27 11

#0  doadump () at pcpu.h:195
195	pcpu.h: No such file or directory.
	in pcpu.h
(kgdb) up 10
#10 0xc062c17b in kern_stat (td=0xc53c5000, path=0xbfbfe2d4 <Address  
0xbfbfe2d4 out of bounds>, pathseg=UIO_USERSPACE, sbp=0xe7debc18) at / 
usr/src/sys/kern/vfs_syscalls.c:2109
2109		if ((error = namei(&nd)) != 0)
(kgdb) bt
#0  doadump () at pcpu.h:195
#1  0xc05b52c5 in boot (howto=260) at /usr/src/sys/kern/ 
kern_shutdown.c:409
#2  0xc05b54d4 in panic (fmt=Variable "fmt" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:563
#3  0xc06e2b97 in ufs_dirbad (ip=0x0, offset=0, how=0xc0795460  
"mangled entry") at /usr/src/sys/ufs/ufs/ufs_lookup.c:598
#4  0xc06e3b5c in ufs_lookup (ap=0xe7deba04) at /usr/src/sys/ufs/ufs/ 
ufs_lookup.c:288
#5  0xc0750f02 in VOP_CACHEDLOOKUP_APV (vop=0xc07d0360, a=0xe7deba04)  
at vnode_if.c:153
#6  0xc0618390 in vfs_cache_lookup (ap=0xe7deba84) at vnode_if.h:83
#7  0xc07528d1 in VOP_LOOKUP_APV (vop=0xc07d0880, a=0xe7deba84) at  
vnode_if.c:99
#8  0xc061e4fc in lookup (ndp=0xe7debba8) at vnode_if.h:57
#9  0xc061f143 in namei (ndp=0xe7debba8) at /usr/src/sys/kern/ 
vfs_lookup.c:219
#10 0xc062c17b in kern_stat (td=0xc53c5000, path=0xbfbfe2d4 <Address  
0xbfbfe2d4 out of bounds>, pathseg=UIO_USERSPACE, sbp=0xe7debc18) at / 
usr/src/sys/kern/vfs_syscalls.c:2109
#11 0xc062c315 in stat (td=0xc53c5000, uap=0xe7debcfc) at /usr/src/sys/ 
kern/vfs_syscalls.c:2093
#12 0xc073c423 in syscall (frame=0xe7debd38) at /usr/src/sys/i386/i386/ 
trap.c:1008
#13 0xc0726b60 in Xint0x80_syscall () at /usr/src/sys/i386/i386/ 
exception.s:196
#14 0x00000033 in ?? ()
Previous frame inner to this frame (corrupt stack?)
(kgdb) up
#11 0xc062c315 in stat (td=0xc53c5000, uap=0xe7debcfc) at /usr/src/sys/ 
kern/vfs_syscalls.c:2093
2093		error = kern_stat(td, uap->path, UIO_USERSPACE, &sb);
(kgdb) p *uap
$1 = {path_l_ = 0xe7debcfc "?⿿?ؿ?Z", path = 0xbfbfe2d4 <Address  
0xbfbfe2d4 out of bounds>, path_r_ = 0xe7debd00 "?ؿ?Z", ub_l_ =  
0xe7debd00 "?ؿ?Z", ub = 0xbfbfd8d4, ub_r_ = 0xe7debd04 "Z"}
(kgdb)