svn commit: r198301 - head/sys/netinet

[Qing Li]

I believe this patch will fix your crash.

-- Qing


On Wed, Oct 21, 2009 at 12:58 AM, Robert Watson <rwatson at freebsd.org> wrote:
> On Tue, 20 Oct 2009, Qing Li wrote:
>
>>  In the ARP callout timer expiration function, the current time_second
>>  is compared against the entry expiration time value (that was set based
>>  on time_second) to check if the current time is larger than the set
>>  expiration time. Due to the +/- timer granularity value, the comparison
>>  returns false, causing the alternative code to be executed. The
>>  alternative code path freed the memory without removing that entry
>>  from the table list, causing a use-after-free bug.
>>
>>  Reviewed by:   discussed with kmacy
>>  MFC after:     immediately
>>  Verified by:   rnoland, yongari
>
> Could this be the same problem I ran into overnight on an 18 October kernel:
>
> Fatal trap 12: page fault while in kernel mode
> cpuid = 0; apic id = 00
> fault virtual address   = 0x7572749f
> fault code              = supervisor read, page not present
> instruction pointer     = 0x20:0xc09c0551
> stack pointer           = 0x28:0xc43f6ab4
> frame pointer           = 0x28:0xc43f6adc
> 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         = 0 (em0 taskq)
>
> #9  0xc0be731b in calltrap () at ../../../i386/i386/exception.s:165
> #10 0xc09c0551 in in_lltable_lookup (llt=0xc4955200, flags=8192,
>    l3addr=0xc43f6b60) at ../../../netinet/in.c:1361
> #11 0xc09b8ea7 in arpintr (m=0xc48dcd00) at if_llatbl.h:202
> #12 0xc096f899 in netisr_dispatch_src (proto=7, source=0, m=0xc48dcd00)
>    at ../../../net/netisr.c:917
> #13 0xc096fb30 in netisr_dispatch (proto=7, m=0xc48dcd00)
>    at ../../../net/netisr.c:1004
> #14 0xc0967c11 in ether_demux (ifp=0xc470b400, m=0xc48dcd00)
>    at ../../../net/if_ethersubr.c:895
> #15 0xc0968163 in ether_input (ifp=0xc470b400, m=0xc48dcd00)
>    at ../../../net/if_ethersubr.c:754
> #16 0xc063bcaa in em_rxeof (adapter=0xc470d000, count=99)
>    at ../../../dev/e1000/if_em.c:4610
> #17 0xc063dfc7 in em_handle_rxtx (context=0xc470d000, pending=1)
>    at ../../../dev/e1000/if_em.c:1763
>
> (kgdb) frame 10
> #10 0xc09c0551 in in_lltable_lookup (llt=0xc4955200, flags=8192,
>    l3addr=0xc43f6b60) at ../../../netinet/in.c:1361
> 1361            LIST_FOREACH(lle, lleh, lle_next) {
> (kgdb) list
> 1356            KASSERT(l3addr->sa_family == AF_INET,
> 1357                ("sin_family %d", l3addr->sa_family));
> 1358
> 1359            hashkey = sin->sin_addr.s_addr;
> 1360            lleh = &llt->lle_head[LLATBL_HASH(hashkey, LLTBL_HASHMASK)];
> 1361            LIST_FOREACH(lle, lleh, lle_next) {
> 1362                    struct sockaddr_in *sa2 = (struct sockaddr_in
> *)L3_ADDR(lle);
> 1363                    if (lle->la_flags & LLE_DELETED)
> 1364                            continue;
> 1365                    if (sa2->sin_addr.s_addr == sin->sin_addr.s_addr)
> (kgdb) print *llt
> $5 = {llt_link = {sle_next = 0x0}, lle_head = {{lh_first = 0xc760d580}, {
>      lh_first = 0x0}, {lh_first = 0x0}, {lh_first = 0xc75c3900}, {
>      lh_first = 0x0} <repeats 14 times>, {lh_first = 0xc49a8380}, {
>      lh_first = 0x0}, {lh_first = 0x0}, {lh_first = 0x0}, {lh_first = 0x0},
> {
>      lh_first = 0x0}, {lh_first = 0x0}, {lh_first = 0x0}, {lh_first = 0x0},
> {
>      lh_first = 0x0}, {lh_first = 0xc61be780}, {lh_first = 0x0}, {
>      lh_first = 0x0}, {lh_first = 0x0}}, llt_af = 2, llt_ifp = 0xc470b400,
>  llt_new = 0xc09bdd60 <in_lltable_new>,
>  llt_free = 0xc09c0490 <in_lltable_free>,
>  llt_prefix_free = 0xc09c09b0 <in_lltable_prefix_free>,
>  llt_lookup = 0xc09c0510 <in_lltable_lookup>,
>  llt_rtcheck = 0xc09bdbe0 <in_lltable_rtcheck>,
>  llt_dump = 0xc09bd9c0 <in_lltable_dump>}
> (kgdb) print *l3addr
> $6 = {sa_len = 16 '\020', sa_family = 2 '\002',
>  sa_data = "\000\000??*\001\000\000\000\000\000\000\000"}
> (kgdb) print lle
> $7 = (struct llentry *) 0x75727473
> (kgdb) print lleh
> $8 = (struct llentries *) 0xc4955210
> (kgdb) print *lleh
> $9 = {lh_first = 0xc75c3900}
>
> Your commit was after this kernel, so I'd be quite happy with the answer
> "now fixed" but wanted to be sure.
>
> Robert
>
>>
>> Modified:
>>  head/sys/netinet/if_ether.c
>>
>> Modified: head/sys/netinet/if_ether.c
>>
>> ==============================================================================
>> --- head/sys/netinet/if_ether.c Tue Oct 20 17:50:36 2009        (r198300)
>> +++ head/sys/netinet/if_ether.c Tue Oct 20 17:55:42 2009        (r198301)
>> @@ -175,18 +175,18 @@ arptimer(void *arg)
>>        CURVNET_SET(ifp->if_vnet);
>>        IF_AFDATA_LOCK(ifp);
>>        LLE_WLOCK(lle);
>> -       if (((lle->la_flags & LLE_DELETED) ||
>> -           (time_second >= lle->la_expire)) &&
>> -           (!callout_pending(&lle->la_timer) &&
>> +       if ((!callout_pending(&lle->la_timer) &&
>>            callout_active(&lle->la_timer))) {
>>                (void) llentry_free(lle);
>>                ARPSTAT_INC(timeouts);
>> -       } else {
>> -               /*
>> -                * Still valid, just drop our reference
>> -                */
>> -               LLE_FREE_LOCKED(lle);
>> +       }
>> +#ifdef DIAGNOSTICS
>> +       else {
>> +               struct sockaddr *l3addr = L3_ADDR(lle);
>> +               log(LOG_INFO, "arptimer issue: %p, IPv4 address:
>> \"%s\"\n", lle,
>> +                   inet_ntoa(((const struct sockaddr_in
>> *)l3addr)->sin_addr));
>>        }
>> +#endif
>>        IF_AFDATA_UNLOCK(ifp);
>>        CURVNET_RESTORE();
>> }
>> @@ -377,7 +377,7 @@ retry:
>>
>>        if (renew) {
>>                LLE_ADDREF(la);
>> -               la->la_expire = time_second;
>> +               la->la_expire = time_second + V_arpt_down;
>>                callout_reset(&la->la_timer, hz * V_arpt_down, arptimer,
>> la);
>>                la->la_asked++;
>>                LLE_WUNLOCK(la);
>>
>