kern/119415: Kernel panic (page fault) with devfs rules

[Jille Timmermans]

>Number:         119415
>Category:       kern
>Synopsis:       Kernel panic (page fault) with devfs rules
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Jan 07 10:50:01 UTC 2008
>Closed-Date:
>Last-Modified:
>Originator:     Jille Timmermans
>Release:        FreeBSD 6.3-PRERELEASE i386
>Organization:
None
>Environment:
FreeBSD blackbox.quis.cx 6.3-PRERELEASE FreeBSD 6.3-PRERELEASE #1: Sun Jan 6 23:24:15 CET 2008 root at blackbox.quis.cx:/usr/obj/usr/src/sys/BLACKBOX i386
FreeBSD istud.quis.cx 6.2-RELEASE-p4 FreeBSD 6.2-RELEASE-p4 #0: Sat May 12 16:41:58 CEST 2007 root at istud.quis.cx:/usr/obj/usr/src/sys/ISTUD i386
>Description:
A kernel panic (page fault) occurs when trying to add/apply rules to a devfs mount.
A value of a null-pointed struct is used in devfs_rule_match().
(/usr/src/sys/fs/devfs/devfs_rule.c:546)

Crash:
Fatal trap 12: page fault while in kernel mode
fault virtual address = 0x4
fault code    = supervisor read, page not present
instruction pointer = 0x20:0xc0528441
stack pointer         = 0x28:0xe57f2b04
frame pointer         = 0x28:0xe57f2b10
code segment    = base 0x0, limit 0xfffff, type 0x1b
      = DPL 0, pres 1, def32 1, gran 1
processor eflags  = interrupt enabled, resume, IOPL = 0
current process   = 721 (devfs)
trap number   = 12
panic: page fault
Uptime: 17s

Backtrace:
#0  doadump () at pcpu.h:165
165 pcpu.h: No such file or directory.
  in pcpu.h
(kgdb) bt
#0  doadump () at pcpu.h:165
#1  0xc0571e10 in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:409
#2  0xc05720bb in panic (fmt=0xc0713e0a "%s")
    at /usr/src/sys/kern/kern_shutdown.c:565
#3  0xc06d9dca in trap_fatal (frame=0xe57f2ac4, eva=4)
    at /usr/src/sys/i386/i386/trap.c:838
#4  0xc06d9afb in trap_pfault (frame=0xe57f2ac4, usermode=0, eva=4)
    at /usr/src/sys/i386/i386/trap.c:745
#5  0xc06d9765 in trap (frame=
      {tf_fs = 8, tf_es = -1066270680, tf_ds = -1056636888, tf_edi = -983976192, tf_esi = -982153344, tf_ebp = -444650736, tf_isp = -44465076
8, tf_ebx = -983976180, tf_edx = -988857600, tf_ecx = -985599760, tf_eax = 0, tf_trapno = 12, tf_err = 0, tf_eip = -1068334015, tf_cs = 32, t
f_eflags = 66182, tf_esp = -983976180, tf_ss = -982153344}) at /usr/src/sys/i386/i386/trap.c:435
#6  0xc06c760a in calltrap () at /usr/src/sys/i386/i386/exception.s:139
#7  0xc0528441 in devfs_rule_match (dk=0xc559b700, de=0xc5758780)
    at /usr/src/sys/fs/devfs/devfs_rule.c:546
#8  0xc05284fe in devfs_rule_run (dk=0xc559b700, de=0xc5758780, depth=1)
    at /usr/src/sys/fs/devfs/devfs_rule.c:588
#9  0xc052812e in devfs_rule_applyde_recursive (dk=0xc559b700, de=0xc5758780)
    at /usr/src/sys/fs/devfs/devfs_rule.c:343
#10 0xc0528117 in devfs_rule_applyde_recursive (dk=0xc559b700, de=0xc5759000)
    at /usr/src/sys/fs/devfs/devfs_rule.c:342
#11 0xc0528149 in devfs_rule_applydm (dk=0xc559b700, dm=0x0)
    at /usr/src/sys/fs/devfs/devfs_rule.c:353
#12 0xc05285fb in devfs_ruleset_applydm (ds=0x0, dm=0xc5759080)
    at /usr/src/sys/fs/devfs/devfs_rule.c:657
#13 0xc0528076 in devfs_rules_ioctl (dm=0xc5759080, cmd=2147632139,
    data=0xc540f0f0 "", td=0xc5395000)
    at /usr/src/sys/fs/devfs/devfs_rule.c:287
#14 0xc052a833 in devfs_rioctl (ap=0xe57f2bf4)
    at /usr/src/sys/fs/devfs/devfs_vnops.c:1115
#15 0xc06eb1ee in VOP_IOCTL_APV (vop=0x0, a=0xe57f2bf4) at vnode_if.c:804
#16 0xc05d1aa1 in vn_ioctl (fp=0xc53cc240, com=2147632139, data=0xc540f0f0,
    active_cred=0xc5758e00, td=0xc5395000) at vnode_if.h:436
#17 0xc0594fe6 in ioctl (td=0xc5395000, uap=0xe57f2d04) at file.h:265
#18 0xc06da057 in syscall (frame=
      {tf_fs = 59, tf_es = 59, tf_ds = 59, tf_edi = 1, tf_esi = -1077940980, tf_ebp = -1077941224, tf_isp = -444650140, tf_ebx = 134525616, t
f_edx = 0, tf_ecx = 0, tf_eax = 54, tf_trapno = 12, tf_err = 2, tf_eip = 672381475, tf_cs = 51, tf_eflags = 582, tf_esp = -1077941252, tf_ss
= 59})
    at /usr/src/sys/i386/i386/trap.c:984
#19 0xc06c765f in Xint0x80_syscall ()
    at /usr/src/sys/i386/i386/exception.s:200
#20 0x00000033 in ?? ()
Previous frame inner to this frame (corrupt stack?)

(kgdb) frame 7
#7  0xc0528441 in devfs_rule_match (dk=0xc559b700, de=0xc5758780)
    at /usr/src/sys/fs/devfs/devfs_rule.c:546
546     if (dev == NULL ||
(kgdb) list
541    * be run (such as if there are no conditions).
542    *
543    * XXX: lacks threadref on dev
544    */
545   if (dr->dr_icond & DRC_DSWFLAGS)
546     if (dev == NULL ||
547         (dev->si_devsw->d_flags & dr->dr_dswflags) == 0)
548       return (0);
549   if (dr->dr_icond & DRC_PATHPTRN)
550     if (!devfs_rule_matchpath(dk, de))
>How-To-Repeat:
# mkdir dev
# mount -t devfs devfs dev
# devfs -m dev ruleset 50
# devfs -m dev rule add type disk hide
# devfs -m dev rule applyset
>Fix:
In /usr/src/sys/fs/devfs/devfs_rule.c:546
  if (dev == NULL ||
Change into:
  if (dev == NULL || dev->si_devsw == NULL ||

I changed this and recompiled, the crash didn't occur anymore.


>Release-Note:
>Audit-Trail:
>Unformatted: