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Date:      Sun, 21 Jul 2013 23:32:17 -0700
From:      Craig Rodrigues <rodrigc@FreeBSD.org>
To:        "freebsd-virtualization@freebsd.org" <freebsd-virtualization@freebsd.org>
Cc:        Adrian Chadd <adrian@freebsd.org>, freebsd-pf@freebsd.org
Subject:   VIMAGE + PF crash in mbuf destructor
Message-ID:  <CAG=rPVfxFiOVOeSyDP=wBubNQCHK5dqcgBBaJjeS6XXtSZSZqg@mail.gmail.com>
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Hi,

I used a kernel config with the following lines:

include GENERIC
options VIMAGE

and compiled a CURRENT kernel from svn://svn.freebsd.org/base/head@253346 .

I also have PF enabled on my system.

Once in a while I have been getting kernel panics like these:


====================================================================
(kgdb) #0  doadump (textdump=1) at pcpu.h:236
#1  0xffffffff808bc617 in kern_reboot (howto=260)
    at /usr/home/rodrigc/freebsd/head/sys/kern/kern_shutdown.c:447
#2  0xffffffff808bcb25 in vpanic (fmt=<value optimized out>,
    ap=<value optimized out>)
    at /usr/home/rodrigc/freebsd/head/sys/kern/kern_shutdown.c:754
#3  0xffffffff808bcb73 in panic (fmt=<value optimized out>)
    at /usr/home/rodrigc/freebsd/head/sys/kern/kern_shutdown.c:683
#4  0xffffffff8033dff7 in db_panic (addr=<value optimized out>,
    have_addr=<value optimized out>, count=<value optimized out>,
    modif=<value optimized out>)
    at /usr/home/rodrigc/freebsd/head/sys/ddb/db_command.c:482
#5  0xffffffff8033dbcd in db_command (cmd_table=<value optimized out>)
    at /usr/home/rodrigc/freebsd/head/sys/ddb/db_command.c:449
#6  0xffffffff8033d944 in db_command_loop ()
    at /usr/home/rodrigc/freebsd/head/sys/ddb/db_command.c:502
#7  0xffffffff803402f0 in db_trap (type=<value optimized out>, code=0)
    at /usr/home/rodrigc/freebsd/head/sys/ddb/db_main.c:231
#8  0xffffffff808f3623 in kdb_trap (type=12, code=0, tf=<value optimized
out>)
    at /usr/home/rodrigc/freebsd/head/sys/kern/subr_kdb.c:654
#9  0xffffffff80cda43a in trap_fatal (frame=0xffffff811dbab6b0,
    eva=<value optimized out>)
    at /usr/home/rodrigc/freebsd/head/sys/amd64/amd64/trap.c:868
#10 0xffffffff80cda6f4 in trap_pfault (frame=0x0, usermode=0)
    at /usr/home/rodrigc/freebsd/head/sys/amd64/amd64/trap.c:699
#11 0xffffffff80cd9ef0 in trap (frame=0xffffff811dbab6b0)
    at /usr/home/rodrigc/freebsd/head/sys/amd64/amd64/trap.c:463
#12 0xffffffff80cc31a2 in calltrap ()
    at /usr/home/rodrigc/freebsd/head/sys/amd64/amd64/exception.S:232
#13 0xffffffff8208f7b7 in pf_mtag_free (t=0xfffffe00a8797870)
    at
/usr/home/rodrigc/freebsd/head/sys/modules/pf/../../netpfil/pf/pf.c:830
#14 0xffffffff808a51c9 in mb_dtor_mbuf (mem=0xfffffe000d0bc500, size=256,
    arg=0x0) at /usr/home/rodrigc/freebsd/head/sys/kern/kern_mbuf.c:499
#15 0xffffffff80b55d4d in uma_zfree_arg (zone=0xfffffe000b4ab900,
    item=0xfffffe000d0bc500, udata=0x0)
    at /usr/home/rodrigc/freebsd/head/sys/vm/uma_core.c:2560
#16 0xffffffff8092d1f5 in m_freem (mb=<value optimized out>) at uma.h:364
#17 0xffffffff8058ba72 in iwn_tx_done (sc=0xffffff8000974000,
    desc=<value optimized out>, ackfailcnt=16, status=131 '\203')
    at /usr/home/rodrigc/freebsd/head/sys/dev/iwn/if_iwn.c:2817
#18 0xffffffff80583e60 in iwn_notif_intr (sc=0xffffff8000974000)
    at /usr/home/rodrigc/freebsd/head/sys/dev/iwn/if_iwn.c:3015
#19 0xffffffff80583684 in iwn_intr (arg=0xffffff8000974000)
    at /usr/home/rodrigc/freebsd/head/sys/dev/iwn/if_iwn.c:3306
#20 0xffffffff8088daf3 in intr_event_execute_handlers (
    p=<value optimized out>, ie=0xfffffe000b696600)
    at /usr/home/rodrigc/freebsd/head/sys/kern/kern_intr.c:1263
#21 0xffffffff8088e4c6 in ithread_loop (arg=0xfffffe000b31b040)
    at /usr/home/rodrigc/freebsd/head/sys/kern/kern_intr.c:1276
#22 0xffffffff8088b3f4 in fork_exit (
    callout=0xffffffff8088e420 <ithread_loop>, arg=0xfffffe000b31b040,
    frame=0xffffff811dbabac0)
    at /usr/home/rodrigc/freebsd/head/sys/kern/kern_fork.c:991
#23 0xffffffff80cc36de in fork_trampoline ()
    at /usr/home/rodrigc/freebsd/head/sys/amd64/amd64/exception.S:606
#24 0x0000000000000000 in ?? ()
Current language:  auto; currently minimal
(kgdb)
====================================================================


It turns out that in this file: src/sys/netpfil/pf/pf.c

    826 static void
    827 pf_mtag_free(struct m_tag *t)
    828 {
    829
    830         uma_zfree(V_pf_mtag_z, t);
    831 }

when line 830 is hit, it turns out that curthread->td_vnet is NULL.

Does anyone have an idea as to the best place
to put CURVNET_SET() to avoid this problem?

I am a little less famiiar with mbuf and pf.

Thanks.
--
Craig

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