Messages in this thread Patch in this message | | | From | Cong Wang <> | Date | Wed, 31 May 2017 16:49:53 -0700 | Subject | Re: net/ipv4: use-after-free in add_grec |
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On Wed, May 31, 2017 at 9:12 AM, Eric Dumazet <eric.dumazet@gmail.com> wrote: > On Wed, 2017-05-31 at 11:46 +0200, Andrey Konovalov wrote: >> Hi, >> >> I've got the following error report while fuzzing the kernel with syzkaller. >> >> On commit 5ed02dbb497422bf225783f46e6eadd237d23d6b (4.12-rc3). >> >> Unfortunately it's not reproducible. >> >> ================================================================== >> BUG: KASAN: use-after-free in add_grec+0x101e/0x1090 net/ipv4/igmp.c:473 >> Read of size 8 at addr ffff88003053c1a0 by task swapper/0/0 >> >> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.12.0-rc3+ #370 >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 >> Call Trace: >> <IRQ> >> __dump_stack lib/dump_stack.c:16 [inline] >> dump_stack+0x292/0x395 lib/dump_stack.c:52 >> print_address_description+0x73/0x280 mm/kasan/report.c:252 >> kasan_report_error mm/kasan/report.c:351 [inline] >> kasan_report+0x22b/0x340 mm/kasan/report.c:408 >> __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429 >> add_grec+0x101e/0x1090 net/ipv4/igmp.c:473 >> igmpv3_send_cr net/ipv4/igmp.c:663 [inline] >> igmp_ifc_timer_expire+0x46d/0xa80 net/ipv4/igmp.c:768 >> IPVS: length: 51 != 8 >> call_timer_fn+0x23f/0x800 kernel/time/timer.c:1268 >> expire_timers kernel/time/timer.c:1307 [inline] >> __run_timers+0x94e/0xcd0 kernel/time/timer.c:1601 >> run_timer_softirq+0x21/0x80 kernel/time/timer.c:1614 >> __do_softirq+0x2fb/0xb99 kernel/softirq.c:284 >> invoke_softirq kernel/softirq.c:364 [inline] >> irq_exit+0x19e/0x1d0 kernel/softirq.c:405 >> exiting_irq arch/x86/include/asm/apic.h:652 [inline] >> smp_apic_timer_interrupt+0x76/0xa0 arch/x86/kernel/apic/apic.c:966 >> apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:481 >> RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53 >> RSP: 0018:ffffffff85a079a8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff10 >> RAX: dffffc0000000020 RBX: 1ffffffff0b40f38 RCX: 0000000000000000 >> RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff85a2a9e4 >> RBP: ffffffff85a079a8 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000000 R12: dffffc0000000000 >> R13: ffffffff85a07a60 R14: ffffffff86171338 R15: 1ffffffff0b40f5b >> </IRQ> >> arch_safe_halt arch/x86/include/asm/paravirt.h:98 [inline] >> default_idle+0x8f/0x440 arch/x86/kernel/process.c:341 >> arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:332 >> default_idle_call+0x36/0x60 kernel/sched/idle.c:98 >> cpuidle_idle_call kernel/sched/idle.c:156 [inline] >> do_idle+0x348/0x420 kernel/sched/idle.c:245 >> cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:350 >> rest_init+0x18d/0x1a0 init/main.c:415 >> start_kernel+0x747/0x779 init/main.c:679 >> x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196 >> x86_64_start_kernel+0x132/0x141 arch/x86/kernel/head64.c:177 >> secondary_startup_64+0x9f/0x9f arch/x86/kernel/head_64.S:304 >> >> Allocated by task 30543: >> save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 >> save_stack+0x43/0xd0 mm/kasan/kasan.c:513 >> set_track mm/kasan/kasan.c:525 [inline] >> kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:617 >> kmem_cache_alloc_trace+0x82/0x270 mm/slub.c:2745 >> kmalloc include/linux/slab.h:492 [inline] >> kzalloc include/linux/slab.h:665 [inline] >> ip_mc_add1_src net/ipv4/igmp.c:1909 [inline] >> ip_mc_add_src+0x6cd/0x1020 net/ipv4/igmp.c:2033 >> ip_mc_msfilter+0x5e5/0xcf0 net/ipv4/igmp.c:2403 >> do_ip_setsockopt.isra.12+0x2d47/0x38c0 net/ipv4/ip_sockglue.c:959 >> ip_setsockopt+0x3a/0xb0 net/ipv4/ip_sockglue.c:1256 >> tcp_setsockopt+0x82/0xd0 net/ipv4/tcp.c:2740 >> sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2844 >> SYSC_setsockopt net/socket.c:1798 [inline] >> SyS_setsockopt+0x270/0x3a0 net/socket.c:1777 >> entry_SYSCALL_64_fastpath+0x1f/0xbe >> >> Freed by task 30543: >> save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 >> save_stack+0x43/0xd0 mm/kasan/kasan.c:513 >> set_track mm/kasan/kasan.c:525 [inline] >> kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:590 >> slab_free_hook mm/slub.c:1357 [inline] >> slab_free_freelist_hook mm/slub.c:1379 [inline] >> slab_free mm/slub.c:2961 [inline] >> kfree+0xe8/0x2b0 mm/slub.c:3882 >> ip_mc_clear_src+0x69/0x1c0 net/ipv4/igmp.c:2078 >> ip_mc_dec_group+0x19a/0x470 net/ipv4/igmp.c:1618 >> ip_mc_drop_socket+0x145/0x230 net/ipv4/igmp.c:2609 >> inet_release+0x4e/0x1c0 net/ipv4/af_inet.c:411 >> sock_release+0x8d/0x1e0 net/socket.c:597 >> sock_close+0x16/0x20 net/socket.c:1072 >> __fput+0x332/0x7f0 fs/file_table.c:209 >> ____fput+0x15/0x20 fs/file_table.c:245 >> task_work_run+0x19b/0x270 kernel/task_work.c:116 >> exit_task_work include/linux/task_work.h:21 [inline] >> do_exit+0x18a3/0x2820 kernel/exit.c:878 >> do_group_exit+0x149/0x420 kernel/exit.c:982 >> get_signal+0x76d/0x1790 kernel/signal.c:2318 >> do_signal+0xd2/0x2130 arch/x86/kernel/signal.c:808 >> exit_to_usermode_loop+0x17a/0x210 arch/x86/entry/common.c:157 >> prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline] >> syscall_return_slowpath+0x3ba/0x410 arch/x86/entry/common.c:263 >> entry_SYSCALL_64_fastpath+0xbc/0xbe >> >> The buggy address belongs to the object at ffff88003053c1a0 >> which belongs to the cache kmalloc-64 of size 64 >> The buggy address is located 0 bytes inside of >> 64-byte region [ffff88003053c1a0, ffff88003053c1e0) >> The buggy address belongs to the page: >> page:ffffea0000c14f00 count:1 mapcount:0 mapping: (null) >> index:0x0 compound_mapcount: 0 >> flags: 0x100000000008100(slab|head) >> raw: 0100000000008100 0000000000000000 0000000000000000 0000000100140014 >> raw: ffffea0000c2f520 ffffea0000e20aa0 ffff88003e80f740 0000000000000000 >> page dumped because: kasan: bad access detected >> >> Memory state around the buggy address: >> ffff88003053c080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >> ffff88003053c100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >> >ffff88003053c180: fc fc fc fc fb fb fb fb fb fb fb fb fc fc fc fc >> ^ >> ffff88003053c200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >> ffff88003053c280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >> ================================================================== > > I have the feeling that ip_mc_clear_src() is called too soon. > > We should call it once all users have released their reference.
In this case, ip_mc_clear_src() is called when the ->users hits zero, therefore I think we possibly miss the refcnt on ->users.
diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c index 44fd86d..c2f3347 100644 --- a/net/ipv4/igmp.c +++ b/net/ipv4/igmp.c @@ -1886,6 +1886,7 @@ static int ip_mc_del_src(struct in_device *in_dev, __be32 *pmca, int sfmode, igmp_ifc_event(pmc->interface); #endif } + pmc->users--; out_unlock: spin_unlock_bh(&pmc->lock); return err; @@ -2025,6 +2026,7 @@ static int ip_mc_add_src(struct in_device *in_dev, __be32 *pmca, int sfmode, #ifdef CONFIG_IP_MULTICAST sf_markstate(pmc); #endif + pmc->users++; isexclude = pmc->sfmode == MCAST_EXCLUDE; if (!delta) pmc->sfcount[sfmode]++;
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