On Fri, Dec 8, 2017 at 4:45 PM, Xin Long <lucien.xin@xxxxxxxxx> wrote: > On Fri, Dec 8, 2017 at 4:16 PM, syzbot > <bot+ed0838d0fa4c4f2b528e20286e6dc63effc7c14d@xxxxxxxxxxxxxxxxxxxxxxxxx> > wrote: >> syzkaller has found reproducer for the following crash on >> 82bcf1def3b5f1251177ad47c44f7e17af039b4b >> git://git.cmpxchg.org/linux-mmots.git/master >> compiler: gcc (GCC) 7.1.1 20170620 >> .config is attached >> Raw console output is attached. >> >> syzkaller reproducer is attached. See https://goo.gl/kgGztJ >> for information about syzkaller reproducers >> >> >> skbuff: skb_over_panic: text:0000000010b86b8d len:196 put:20 >> head:000000003b477e60 data:000000000e85441e tail:0xd4 end:0xc0 dev:lo >> ------------[ cut here ]------------ >> kernel BUG at net/core/skbuff.c:104! >> invalid opcode: 0000 [#1] SMP KASAN >> Dumping ftrace buffer: >> (ftrace buffer empty) >> Modules linked in: >> CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.15.0-rc2-mm1+ #39 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS >> Google 01/01/2011 >> RIP: 0010:skb_panic+0x15c/0x1f0 net/core/skbuff.c:100 >> RSP: 0018:ffff8801db307508 EFLAGS: 00010286 >> RAX: 0000000000000082 RBX: ffff8801c517e840 RCX: 0000000000000000 >> RDX: 0000000000000082 RSI: 1ffff1003b660e61 RDI: ffffed003b660e95 >> RBP: ffff8801db307570 R08: 1ffff1003b660e23 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff85bd4020 >> R13: ffffffff84754ed2 R14: 0000000000000014 R15: ffff8801c4e26540 >> FS: 0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: 0000000000463610 CR3: 00000001c6698000 CR4: 00000000001406e0 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> Call Trace: >> <IRQ> >> skb_over_panic net/core/skbuff.c:109 [inline] >> skb_put+0x181/0x1c0 net/core/skbuff.c:1694 >> add_grhead.isra.24+0x42/0x3b0 net/ipv6/mcast.c:1695 >> add_grec+0xa55/0x1060 net/ipv6/mcast.c:1817 >> mld_send_cr net/ipv6/mcast.c:1903 [inline] >> mld_ifc_timer_expire+0x4d2/0x770 net/ipv6/mcast.c:2448 >> call_timer_fn+0x23b/0x840 kernel/time/timer.c:1320 >> expire_timers kernel/time/timer.c:1357 [inline] >> __run_timers+0x7e1/0xb60 kernel/time/timer.c:1660 >> run_timer_softirq+0x4c/0xb0 kernel/time/timer.c:1686 >> __do_softirq+0x29d/0xbb2 kernel/softirq.c:285 >> invoke_softirq kernel/softirq.c:365 [inline] >> irq_exit+0x1d3/0x210 kernel/softirq.c:405 >> exiting_irq arch/x86/include/asm/apic.h:540 [inline] >> smp_apic_timer_interrupt+0x16b/0x700 arch/x86/kernel/apic/apic.c:1052 >> apic_timer_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:920 >> </IRQ> >> RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54 >> RSP: 0018:ffff8801d9f97da8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff11 >> RAX: dffffc0000000000 RBX: 1ffff1003b3f2fb8 RCX: 0000000000000000 >> RDX: 1ffffffff0c59734 RSI: 0000000000000001 RDI: ffffffff862cb9a0 >> RBP: ffff8801d9f97da8 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001 >> R13: ffff8801d9f97e60 R14: ffffffff869eb920 R15: 0000000000000000 >> arch_safe_halt arch/x86/include/asm/paravirt.h:93 [inline] >> default_idle+0xbf/0x430 arch/x86/kernel/process.c:355 >> arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:346 >> default_idle_call+0x36/0x90 kernel/sched/idle.c:98 >> cpuidle_idle_call kernel/sched/idle.c:156 [inline] >> do_idle+0x24a/0x3b0 kernel/sched/idle.c:246 >> cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:351 >> start_secondary+0x330/0x460 arch/x86/kernel/smpboot.c:277 >> secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:237 >> Code: 03 0f b6 04 01 84 c0 74 04 3c 03 7e 20 8b 4b 78 41 57 48 c7 c7 a0 38 >> bd 85 52 56 4c 89 ea 41 50 4c 89 e6 45 89 f0 e8 0c b6 3d fd <0f> 0b 4c 89 4d >> b8 4c 89 45 c0 48 89 75 c8 48 89 55 d0 e8 7d 93 >> RIP: skb_panic+0x15c/0x1f0 net/core/skbuff.c:100 RSP: ffff8801db307508 >> ---[ end trace 941a8a0f633e271f ]--- >> > This isn't a sctp problem, but mld's, seems when lo's mtu became 0, > it allocs a skb without enough space in add_grec(): > if (AVAILABLE(skb) < sizeof(*psrc) + > first*sizeof(struct mld2_grec)) { > if (truncate && !first) > break; /* truncate these */ > if (pgr) > pgr->grec_nsrcs = htons(scount); > if (skb) > mld_sendpack(skb); > skb = mld_newpack(idev, dev->mtu); <--- > > I will check this for sure later on both igmp and mld. Fix: --- a/net/ipv6/mcast.c +++ b/net/ipv6/mcast.c @@ -1766,8 +1766,8 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ifmcaddr6 *pmc, if (isquery) psf->sf_gsresp = 0; - if (AVAILABLE(skb) < sizeof(*psrc) + - first*sizeof(struct mld2_grec)) { + if (AVAILABLE(skb) < (int)(sizeof(*psrc) + + first * sizeof(*pgr))) { if (truncate && !first) break; /* truncate these */ if (pgr) @@ -1810,7 +1810,7 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ifmcaddr6 *pmc, return skb; if (pmc->mca_crcount || isquery || crsend) { /* make sure we have room for group header */ - if (skb && AVAILABLE(skb) < sizeof(struct mld2_grec)) { + if (skb && AVAILABLE(skb) < (int)sizeof(*pgr)) { mld_sendpack(skb); skb = NULL; /* add_grhead will get a new one */ } do the same on igmp. -- To unsubscribe from this list: send the line "unsubscribe linux-sctp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html