Date: Wed, 21 Oct 2009 08:58:19 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: Qing Li <qingli@FreeBSD.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r198301 - head/sys/netinet Message-ID: <alpine.BSF.2.00.0910210853540.24137@fledge.watson.org> In-Reply-To: <200910201755.n9KHtgT9073966@svn.freebsd.org> References: <200910201755.n9KHtgT9073966@svn.freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
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);
>
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?alpine.BSF.2.00.0910210853540.24137>