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Date: Mon, 14 Jan 2019 12:58:02 +0100
From: Dmitry Vyukov <dvyukov@...gle.com>
To: zzoru <zzoru007@...il.com>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>,
Kirill Tkhai <ktkhai@...tuozzo.com>,
"davem@...emloft.net" <davem@...emloft.net>,
Andrey Vagin <avagin@...tuozzo.com>,
"dsahern@...il.com" <dsahern@...il.com>,
"nicolas.dichtel@...nd.com" <nicolas.dichtel@...nd.com>,
"tyhicks@...onical.com" <tyhicks@...onical.com>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"syzkaller@...glegroups.com" <syzkaller@...glegroups.com>
Subject: Re: net/core: BUG in copy_net_ns()
On Sat, Jan 12, 2019 at 11:34 AM zzoru <zzoru007@...il.com> wrote:
>
> Probably, there is a memory bug on net object by setup_net() -> ops_init(). (ipv4_sysctl_init_net, ipmr_net_init, etc...)
> I also found that this bug can reproduce v4.18-rc1~
>
> On Sat, Jan 12, 2019 at 8:51 AM Eric W. Biederman <ebiederm@...ssion.com> wrote:
>>
>> zzoru <zzoru007@...il.com> writes:
>>
>> >> I received 3 spam messages from this address today.
>> >> We can simply ignore this report.
>> > I already mentioned about this.
>> >
>> >> and, sorry for my encrypted mails.
>> >> I don't understand this failure report at all.
>> >>
>> >> I don't see the connection to copy_net_ns(). And I don't see how the
>> >> suggested patch short of covering up a memory stomp could possibly make
>> >> a difference.
>> >>
>> >> What am I missing?
>> >> void execute_one(void)
>> >> {
>> >> syscall(__NR_unshare, 0x40000000);
>> >> }
>> > ksys_unshare -> unshare_nsproxy_namespaces -> create_new_namespaces ->
>> > copy_net_ns
>> > unshare(CLONE_NEWNET) calls copy_net_ns() (It requires the CAP_SYS_ADMIN
>> > capability)
>>
>> Looking at your alternate patch where you switch the structure
>> order it looks like there is a memory stomp. Probably a use
>> after free. It is a shame that KASAN is not catching the problem.
>> That is my only suggestion at the moment.
>>
>> The OOM may be because network namespaces are created in quick
>> succession and they take a while to free.
>>
>> One of the nasty truths about testing is sometimes you can be testing
>> one thing and you can trigger a bug in something completely different.
>> Right now it looks like anything that copy_net_ns calls could be
>> responsible for the memory problems.
This looks superciliously similar to:
https://groups.google.com/d/msg/syzkaller-bugs/nFeC8-UG1gg/B6GFaZFrFQAJ
The crux: for the last ~half a year low memory conditions randomly
corrupt kernel memory with stack overflows.
>> > I made many error reports about this bug, and the other one is
>> >
>> > [ 90.289025] WARNING: CPU: 1 PID: 1732 at mm/page_alloc.c:4415
>> > __alloc_pages_slowpath+0x1cb1/0x2220
>> > [ 90.290223] Modules linked in:
>> > [ 90.290639] CPU: 1 PID: 1732 Comm: kworker/u4:5 Not tainted 5.0.0-rc1+ #6
>> > [ 90.291475] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>> > BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
>> > [ 90.292681] Workqueue: writeback wb_workfn (flush-8:0)
>> > [ 90.293350] RIP: 0010:__alloc_pages_slowpath+0x1cb1/0x2220
>> > [ 90.294075] Code: 8b 84 24 a8 00 00 00 e9 ea f1 ff ff 85 d2 0f 85 0b
>> > 01 00 00 48 c7 c7 c0 5e 55 84 e8 79 f8 23 02 e9 86 f9 ff ff 44 8b 74 24
>> > 0c <0f> 0b 48 b8 00 00 00 00 00 fc ff df 48 8b 54 24 18 48 c1 ea 03 80
>> > [ 90.296527] RSP: 0018:ffff888064276dd8 EFLAGS: 00010046
>> > [ 90.297203] RAX: 0000000000000000 RBX: 0000000000000000 RCX:
>> > 1ffff1100c84eda8
>> > [ 90.297784] kmemleak: Cannot allocate a kmemleak_object structure
>> > [ 90.298186] RDX: 0000000000000000 RSI: 0000000000000000 RDI:
>> > ffff88807ffdd528
>> > [ 90.298242] RBP: dffffc0000000000 R08: 0000000000000000 R09:
>> > 0000000000000679
>> > [ 90.298247] R10: 0000000000000000 R11: ffff88807ffdc487 R12:
>> > 0000000000000000
>> > [ 90.298251] R13: ffff888064277030 R14: 0000000000415a00 R15:
>> > ffff888064277030
>> > [ 90.298257] FS: 0000000000000000(0000) GS:ffff88806d500000(0000)
>> > knlGS:0000000000000000
>> > [ 90.298262] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> > [ 90.298267] CR2: 00007fff6ac6a718 CR3: 0000000056578000 CR4:
>> > 00000000000006e0
>> > [ 90.298272] Call Trace:
>> > [ 90.298283] ? __alloc_pages_slowpath+0x1ce6/0x2220
>> > [ 90.298299] ? warn_alloc+0x120/0x120
>> > [ 90.302432] kmemleak: Kernel memory leak detector disabled
>> > [ 90.303346] ? lock_acquire+0x103/0x2e0
>> > [ 90.303358] ? __isolate_free_page+0x4b0/0x4b0
>> > [ 90.303366] ? __lock_is_held+0xad/0x140
>> > [ 90.303377] __alloc_pages_nodemask+0x521/0x5f0
>> > [ 90.303386] ? __alloc_pages_slowpath+0x2220/0x2220
>> > [ 90.315010] cache_grow_begin+0x95/0x300
>> > [ 90.315613] fallback_alloc+0x1ce/0x270
>> > [ 90.316211] ? mempool_free+0x360/0x360
>> > [ 90.316767] kmem_cache_alloc+0x286/0x2f0
>> > [ 90.317348] ? mempool_free+0x360/0x360
>> > [ 90.317919] create_object+0x83/0x880
>> > [ 90.318517] ? kmemleak_disable+0x90/0x90
>> > [ 90.319103] ? mark_held_locks+0xc1/0x140
>> > [ 90.319679] ? kmem_cache_alloc+0x9c/0x2f0
>> > [ 90.320307] ? mempool_free+0x360/0x360
>> > [ 90.320900] kmem_cache_alloc+0x18f/0x2f0
>> > [ 90.321650] ? mempool_free+0x360/0x360
>> > [ 90.322228] mempool_alloc+0x13e/0x340
>> > [ 90.322765] ? mempool_destroy+0x30/0x30
>> > [ 90.323370] ? mark_held_locks+0xc1/0x140
>> > [ 90.323993] ? _raw_spin_unlock_irqrestore+0x3e/0x50
>> > [ 90.324786] bio_alloc_bioset+0x36f/0x5d0
>> > [ 90.325397] ? __test_set_page_writeback+0x136/0x960
>> > [ 90.326161] ? bvec_alloc+0x2d0/0x2d0
>> > [ 90.326708] ? wait_for_stable_page+0x290/0x290
>> > [ 90.327392] submit_bh_wbc.isra.57+0x128/0x680
>> > [ 90.328053] ? create_page_buffers+0x111/0x200
>> > [ 90.328685] __block_write_full_page+0x6e8/0xcd0
>> > [ 90.329339] ? check_disk_change+0x130/0x130
>> > [ 90.329966] block_write_full_page+0x202/0x250
>> > [ 90.330675] ? check_disk_change+0x130/0x130
>> > [ 90.331291] __writepage+0x62/0xe0
>> > [ 90.331786] write_cache_pages+0x5b8/0xf60
>> > [ 90.332375] ? __wb_calc_thresh+0x290/0x290
>> > [ 90.332976] ? clear_page_dirty_for_io+0x5c0/0x5c0
>> > [ 90.333686] ? mark_held_locks+0x140/0x140
>> > [ 90.334301] ? print_circular_bug_entry+0x1f/0x60
>> > [ 90.334999] ? __lock_acquire+0x5d6/0x4630
>> > [ 90.335621] generic_writepages+0xda/0x150
>> > [ 90.336243] ? write_cache_pages+0xf60/0xf60
>> > [ 90.336852] ? mark_held_locks+0x140/0x140
>> > [ 90.337453] ? blkdev_readpages+0x30/0x30
>> > [ 90.338020] do_writepages+0xf0/0x290
>> > [ 90.338611] ? page_writeback_cpu_online+0x10/0x10
>> > [ 90.339324] ? __lock_is_held+0xad/0x140
>> > [ 90.339900] __writeback_single_inode+0xf3/0x1000
>> > [ 90.340587] writeback_sb_inodes+0x4e7/0xce0
>> > [ 90.341214] ? __writeback_single_inode+0x1000/0x1000
>> > [ 90.341929] ? down_read_trylock+0x5b/0x90
>> > [ 90.342579] ? trylock_super+0x1d/0x100
>> > [ 90.343162] __writeback_inodes_wb+0x109/0x220
>> > [ 90.343799] wb_writeback+0x7a1/0xb90
>> > [ 90.344347] ? writeback_inodes_wb.constprop.44+0x190/0x190
>> > [ 90.345143] ? cpumask_next+0x1f/0x30
>> > [ 90.345679] ? find_next_bit+0x101/0x130
>> > [ 90.346281] ? get_nr_dirty_inodes+0xd0/0x130
>> > [ 90.346909] wb_workfn+0x921/0xec0
>> > [ 90.347397] ? process_one_work+0xadd/0x1bb0
>> > [ 90.348025] ? inode_wait_for_writeback+0x30/0x30
>> > [ 90.348700] process_one_work+0xbbd/0x1bb0
>> > [ 90.349314] ? max_active_store+0x130/0x130
>> > [ 90.349915] ? do_raw_spin_lock+0x11b/0x280
>> > [ 90.350557] worker_thread+0x8c/0x1060
>> > [ 90.351096] ? __kthread_parkme+0xf8/0x1a0
>> > [ 90.351673] ? process_one_work+0x1bb0/0x1bb0
>> > [ 90.352334] kthread+0x347/0x410
>> > [ 90.352798] ? kthread_create_worker_on_cpu+0xe0/0xe0
>> > [ 90.353509] ret_from_fork+0x3a/0x50
>> > [ 90.354020] irq event stamp: 282384
>> > [ 90.354590] hardirqs last enabled at (282383): [<ffffffff8160678c>]
>> > kmem_cache_alloc+0x9c/0x2f0
>> > [ 90.355832] hardirqs last disabled at (282384): [<ffffffff8160674d>]
>> > kmem_cache_alloc+0x5d/0x2f0
>> > [ 90.357066] softirqs last enabled at (282196): [<ffffffff816daa87>]
>> > wb_workfn+0x387/0xec0
>> > [ 90.358280] softirqs last disabled at (282194): [<ffffffff816da918>]
>> > wb_workfn+0x218/0xec0
>> > [ 90.359426] ---[ end trace 71c4462c6227f0d8 ]---
>> > [ 90.360135] kmemleak: Cannot allocate a kmemleak_object structure
>> > [ 90.888624] a.out invoked oom-killer:
>> > gfp_mask=0x6040d0(GFP_KERNEL|__GFP_COMP|__GFP_RECLAIMABLE), order=0,
>> > oom_score_adj=0
>> > [ 90.890564] CPU: 0 PID: 22248 Comm: a.out Tainted: G W
>> > 5.0.0-rc1+ #6
>> > [ 90.891793] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>> > BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
>> > [ 90.893263] Call Trace:
>> > [ 90.893678] dump_stack+0xca/0x13e
>> > [ 90.894242] dump_header+0x108/0xaef
>> > [ 90.894822] ? ___ratelimit+0x5b/0x436
>> > [ 90.895430] oom_kill_process.cold.38+0x10/0xa87
>> > [ 90.896164] ? lock_downgrade+0x5d0/0x5d0
>> > [ 90.896806] ? _raw_spin_unlock+0x1f/0x30
>> > [ 90.897445] ? oom_badness+0xc8/0x770
>> > [ 90.898045] out_of_memory+0x32a/0x1ab0
>> > [ 90.898668] ? oom_killer_disable+0x280/0x280
>> > [ 90.899365] ? mutex_trylock+0x162/0x1a0
>> > [ 90.899998] __alloc_pages_slowpath+0x1b7a/0x2220
>> > [ 90.900754] ? warn_alloc+0x120/0x120
>> > [ 90.901344] ? find_held_lock+0x33/0x1c0
>> > [ 90.901985] __alloc_pages_nodemask+0x521/0x5f0
>> > [ 90.902723] ? __alloc_pages_slowpath+0x2220/0x2220
>> > [ 90.903499] ? mark_held_locks+0xc1/0x140
>> > [ 90.904137] ? cache_grow_begin+0x28f/0x300
>> > [ 90.904807] cache_grow_begin+0x95/0x300
>> > [ 90.905443] fallback_alloc+0x1ce/0x270
>> > [ 90.906074] kmem_cache_alloc+0x286/0x2f0
>> > [ 90.906720] ? sock_destroy_inode+0x60/0x60
>> > [ 90.907392] sock_alloc_inode+0x18/0x250
>> > [ 90.908021] ? sock_destroy_inode+0x60/0x60
>> > [ 90.908690] alloc_inode+0x5e/0x180
>> > [ 90.909254] new_inode_pseudo+0x12/0xd0
>> > [ 90.909868] sock_alloc+0x3c/0x270
>> > [ 90.910428] __sock_create+0xbe/0x740
>> > [ 90.911026] inet_ctl_sock_create+0x8c/0x1e0
>> > [ 90.911710] ? inet_current_timestamp+0xc0/0xc0
>> > [ 90.912432] ? rcu_read_lock_sched_held+0x10f/0x130
>> > [ 90.913205] ? find_next_bit+0x101/0x130
>> > [ 90.913837] icmpv6_sk_init+0x12a/0x2b0
>> > [ 90.914463] ? inet6_net_init+0x437/0x7c0
>> > [ 90.915102] ? icmpv6_err_convert+0x180/0x180
>> > [ 90.915799] ? ac6_proc_init+0x5a/0x70
>> > [ 90.916402] ? inet6_net_init+0x53b/0x7c0
>> > [ 90.917041] ? icmpv6_err_convert+0x180/0x180
>> > [ 90.917734] ops_init+0xb2/0x400
>> > [ 90.918265] setup_net+0x24c/0x5e0
>> > [ 90.918817] ? ops_init+0x400/0x400
>> > [ 90.919386] copy_net_ns+0x1a2/0x270
>> > [ 90.919969] create_new_namespaces+0x579/0x790
>> > [ 90.920676] unshare_nsproxy_namespaces+0xc3/0x190
>> > [ 90.921435] ksys_unshare+0x428/0x810
>> > [ 90.922029] ? walk_process_tree+0x2c0/0x2c0
>> > [ 90.922712] ? __change_pid+0x19c/0x2c0
>> > [ 90.923328] ? _raw_write_unlock_irq+0x24/0x30
>> > [ 90.924038] ? trace_hardirqs_on_thunk+0x1a/0x1c
>> > [ 90.924771] ? trace_hardirqs_off_caller+0x55/0x1c0
>> > [ 90.925547] __x64_sys_unshare+0x2d/0x40
>> > [ 90.926187] do_syscall_64+0xbc/0x4e0
>> > [ 90.926777] entry_SYSCALL_64_after_hwframe+0x49/0xbe
>> > [ 90.927573] RIP: 0033:0x7f827ad52229
>> > [ 90.928146] Code: Bad RIP value.
>> > [ 90.928663] RSP: 002b:00007fff6ac6a6c8 EFLAGS: 00000217 ORIG_RAX:
>> > 0000000000000110
>> > [ 90.929837] RAX: ffffffffffffffda RBX: 0000000000000000 RCX:
>> > 00007f827ad52229
>> > [ 90.930952] RDX: 00007f827ad27147 RSI: 0000000000000000 RDI:
>> > 0000000040000000
>> > [ 90.932056] RBP: 00007fff6ac6a6d0 R08: 0000000000000005 R09:
>> > 00007fff6ac6a720
>> > [ 90.933165] R10: 0000000000000000 R11: 0000000000000217 R12:
>> > 00005607242822e0
>> > [ 90.934278] R13: 00007fff6ac6a830 R14: 0000000000000000 R15:
>> > 0000000000000000
>> >
>> > I just guess that copy_net_ns func doesn't call net_free, and it makes OOM.
>> >
>> > And, I found that
>> >
>> > diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
>> > index 99d4148e0f90..38c474e4ab4c 100644
>> > --- a/include/net/net_namespace.h
>> > +++ b/include/net/net_namespace.h
>> > @@ -50,12 +50,12 @@ struct bpf_prog;
>> > #define NETDEV_HASHENTRIES (1 << NETDEV_HASHBITS)
>> >
>> > struct net {
>> > - refcount_t passive; /* To decided when the
>> > network
>> > - * namespace should be
>> > freed.
>> > - */
>> > refcount_t count; /* To decided when the
>> > network
>> > * namespace should be
>> > shut down.
>> > */
>> > + refcount_t passive; /* To decided when the
>> > network
>> > + * namespace should be
>> > freed.
>> > + */
>> > spinlock_t rules_mod_lock;
>> >
>> > atomic64_t cookie_gen;
>> >
>> > this patch also works on this bug. (Just swap the order of net struct.)
>> > I don't know why this patch works (I just thought that compiler
>> > optimization issue can make this bug and try this one.)
>> > I need to review code more on copy_net_ns().
>> >
>> > Also, I reproduce this bug on Ubuntu 18.10 (4.18.0-10-generic) on VMWare
>> > Workstation Pro 15.0.2 by C reproducer.
>> >
>> > On 12/01/2019 5:41 오전, Kirill Tkhai wrote:
>> >> On 11.01.2019 23:33, Eric W. Biederman wrote:
>> >>> zzoru <zzoru007@...il.com> writes:
>> >>>
>> >>>> net/core: BUG in copy_net_ns() (net_namespace.c)
>> >>> I don't understand this failure report at all.
>> >>>
>> >>> I don't see the connection to copy_net_ns(). And I don't see how the
>> >>> suggested patch short of covering up a memory stomp could possibly make
>> >>> a difference.
>> >>>
>> >>> What am I missing?
>> >> I received 3 spam messages from this address today.
>> >> We can simply ignore this report.
>> >>
>> >>>
>> >>>> Hello,
>> >>>>
>> >>>> I've got the following error report while fuzzing the kernel with syzkaller.
>> >>>>
>> >>>> On commit 1bdbe227492075d058e37cb3d400e6468d0095b5
>> >>>>
>> >>>> Syzkaller hit 'WARNING in __alloc_pages_slowpath' bug.
>> >>>>
>> >>>> syz-executor561 (17453) used greatest stack depth: 25056 bytes left
>> >>>> WARNING: CPU: 0 PID: 692 at mm/page_alloc.c:4415
>> >>>> __alloc_pages_slowpath+0x1cb1/0x2220 mm/page_alloc.c:4386
>> >>>> Kernel panic - not syncing: panic_on_warn set ...
>> >>>> CPU: 0 PID: 692 Comm: kswapd0 Not tainted 5.0.0-rc1+ #4
>> >>>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
>> >>>> Ubuntu-1.8.2-1ubuntu1 04/01/2014
>> >>>> Call Trace:
>> >>>> __dump_stack lib/dump_stack.c:77 [inline]
>> >>>> dump_stack+0xca/0x13e lib/dump_stack.c:113
>> >>>> panic+0x278/0x5bf kernel/panic.c:214
>> >>>> __warn.cold.10+0x20/0x45 kernel/panic.c:571
>> >>>> report_bug+0x246/0x2d0 lib/bug.c:186
>> >>>> fixup_bug arch/x86/kernel/traps.c:178 [inline]
>> >>>> do_error_trap+0x123/0x1e0 arch/x86/kernel/traps.c:271
>> >>>> do_invalid_op+0x31/0x40 arch/x86/kernel/traps.c:290
>> >>>> invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
>> >>>> RIP: 0010:__alloc_pages_slowpath+0x1cb1/0x2220 mm/page_alloc.c:4415
>> >>>> Code: 8b 84 24 a8 00 00 00 e9 ea f1 ff ff 85 d2 0f 85 0b 01 00 00 48 c7
>> >>>> c7 c0 5e 55 84 e8 79 f8 23 02 e9 86 f9 ff ff 44 8b 74 24 0c <0f> 0b 48
>> >>>> b8 00 00 00 00 00 fc ff df 48 8b 54 24 18 48 c1 ea 03 80
>> >>>> RSP: 0018:ffff8880683fedb8 EFLAGS: 00010046
>> >>>> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 1ffff1100d07fda4
>> >>>> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88807ffdd528
>> >>>> RBP: dffffc0000000000 R08: 0000000000000000 R09: 000000000000067a
>> >>>> R10: 0000000000000000 R11: ffff88807ffdc487 R12: 0000000000000000
>> >>>> R13: ffff8880683ff010 R14: 0000000000415a00 R15: ffff8880683ff010
>> >>>> __alloc_pages_nodemask+0x521/0x5f0 mm/page_alloc.c:4555
>> >>>> __alloc_pages include/linux/gfp.h:473 [inline]
>> >>>> __alloc_pages_node include/linux/gfp.h:486 [inline]
>> >>>> kmem_getpages mm/slab.c:1398 [inline]
>> >>>> cache_grow_begin+0x95/0x300 mm/slab.c:2666
>> >>>> fallback_alloc+0x1ce/0x270 mm/slab.c:3208
>> >>>> __do_cache_alloc mm/slab.c:3345 [inline]
>> >>>> slab_alloc mm/slab.c:3373 [inline]
>> >>>> kmem_cache_alloc+0x286/0x2f0 mm/slab.c:3541
>> >>>> create_object+0x83/0x880 mm/kmemleak.c:578
>> >>>> kmemleak_alloc_recursive include/linux/kmemleak.h:55 [inline]
>> >>>> slab_post_alloc_hook mm/slab.h:442 [inline]
>> >>>> slab_alloc mm/slab.c:3381 [inline]
>> >>>> kmem_cache_alloc+0x18f/0x2f0 mm/slab.c:3541
>> >>>> mempool_alloc+0x13e/0x340 mm/mempool.c:385
>> >>>> bio_alloc_bioset+0x36f/0x5d0 block/bio.c:489
>> >>>> bio_alloc include/linux/bio.h:393 [inline]
>> >>>> submit_bh_wbc.isra.57+0x128/0x680 fs/buffer.c:3061
>> >>>> __block_write_full_page+0x6e8/0xcd0 fs/buffer.c:1765
>> >>>> block_write_full_page+0x202/0x250 fs/buffer.c:2955
>> >>>> pageout mm/vmscan.c:865 [inline]
>> >>>> shrink_page_list+0x220f/0x3800 mm/vmscan.c:1383
>> >>>> shrink_inactive_list+0x3c2/0xaa0 mm/vmscan.c:1961
>> >>>> shrink_list mm/vmscan.c:2273 [inline]
>> >>>> shrink_node_memcg.constprop.83+0x4bf/0x10e0 mm/vmscan.c:2538
>> >>>> shrink_node+0x162/0xd10 mm/vmscan.c:2753
>> >>>> kswapd_shrink_node mm/vmscan.c:3516 [inline]
>> >>>> balance_pgdat+0x47f/0xc00 mm/vmscan.c:3674
>> >>>> kswapd+0x57c/0xde0 mm/vmscan.c:3929
>> >>>> kthread+0x347/0x410 kernel/kthread.c:246
>> >>>> ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
>> >>>> Dumping ftrace buffer:
>> >>>> (ftrace buffer empty)
>> >>>> Kernel Offset: disabled
>> >>>> Rebooting in 86400 seconds..
>> >>>>
>> >>>>
>> >>>> Syzkaller reproducer:
>> >>>> # {Threaded:false Collide:false Repeat:true RepeatTimes:0 Procs:8
>> >>>> Sandbox:none Fault:false FaultCall:-1 FaultNth:0 EnableTun:false
>> >>>> UseTmpDir:true EnableCgroups:false EnableNetdev:true ResetNet:false
>> >>>> HandleSegv:false Repro:false Trace:false}
>> >>>> unshare(0x40000000)
>> >>>>
>> >>>>
>> >>>> C reproducer:
>> >>>> // autogenerated by syzkaller (https://github.com/google/syzkaller)
>> >>>>
>> >>>> #define _GNU_SOURCE
>> >>>>
>> >>>> #include <arpa/inet.h>
>> >>>> #include <dirent.h>
>> >>>> #include <endian.h>
>> >>>> #include <errno.h>
>> >>>> #include <fcntl.h>
>> >>>> #include <net/if.h>
>> >>>> #include <net/if_arp.h>
>> >>>> #include <netinet/in.h>
>> >>>> #include <sched.h>
>> >>>> #include <signal.h>
>> >>>> #include <stdarg.h>
>> >>>> #include <stdbool.h>
>> >>>> #include <stdint.h>
>> >>>> #include <stdio.h>
>> >>>> #include <stdlib.h>
>> >>>> #include <string.h>
>> >>>> #include <sys/ioctl.h>
>> >>>> #include <sys/mount.h>
>> >>>> #include <sys/prctl.h>
>> >>>> #include <sys/resource.h>
>> >>>> #include <sys/socket.h>
>> >>>> #include <sys/stat.h>
>> >>>> #include <sys/syscall.h>
>> >>>> #include <sys/time.h>
>> >>>> #include <sys/types.h>
>> >>>> #include <sys/uio.h>
>> >>>> #include <sys/wait.h>
>> >>>> #include <time.h>
>> >>>> #include <unistd.h>
>> >>>>
>> >>>> #include <linux/if_addr.h>
>> >>>> #include <linux/if_ether.h>
>> >>>> #include <linux/if_link.h>
>> >>>> #include <linux/if_tun.h>
>> >>>> #include <linux/in6.h>
>> >>>> #include <linux/ip.h>
>> >>>> #include <linux/neighbour.h>
>> >>>> #include <linux/net.h>
>> >>>> #include <linux/netlink.h>
>> >>>> #include <linux/rtnetlink.h>
>> >>>> #include <linux/tcp.h>
>> >>>> #include <linux/veth.h>
>> >>>>
>> >>>> unsigned long long procid;
>> >>>>
>> >>>> static void sleep_ms(uint64_t ms)
>> >>>> {
>> >>>> usleep(ms * 1000);
>> >>>> }
>> >>>>
>> >>>> static uint64_t current_time_ms(void)
>> >>>> {
>> >>>> struct timespec ts;
>> >>>> if (clock_gettime(CLOCK_MONOTONIC, &ts))
>> >>>> exit(1);
>> >>>> return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000;
>> >>>> }
>> >>>>
>> >>>> static void use_temporary_dir(void)
>> >>>> {
>> >>>> char tmpdir_template[] = "./syzkaller.XXXXXX";
>> >>>> char* tmpdir = mkdtemp(tmpdir_template);
>> >>>> if (!tmpdir)
>> >>>> exit(1);
>> >>>> if (chmod(tmpdir, 0777))
>> >>>> exit(1);
>> >>>> if (chdir(tmpdir))
>> >>>> exit(1);
>> >>>> }
>> >>>>
>> >>>> static bool write_file(const char* file, const char* what, ...)
>> >>>> {
>> >>>> char buf[1024];
>> >>>> va_list args;
>> >>>> va_start(args, what);
>> >>>> vsnprintf(buf, sizeof(buf), what, args);
>> >>>> va_end(args);
>> >>>> buf[sizeof(buf) - 1] = 0;
>> >>>> int len = strlen(buf);
>> >>>> int fd = open(file, O_WRONLY | O_CLOEXEC);
>> >>>> if (fd == -1)
>> >>>> return false;
>> >>>> if (write(fd, buf, len) != len) {
>> >>>> int err = errno;
>> >>>> close(fd);
>> >>>> errno = err;
>> >>>> return false;
>> >>>> }
>> >>>> close(fd);
>> >>>> return true;
>> >>>> }
>> >>>>
>> >>>> static struct {
>> >>>> char* pos;
>> >>>> int nesting;
>> >>>> struct nlattr* nested[8];
>> >>>> char buf[1024];
>> >>>> } nlmsg;
>> >>>>
>> >>>> static void netlink_init(int typ, int flags, const void* data, int size)
>> >>>> {
>> >>>> memset(&nlmsg, 0, sizeof(nlmsg));
>> >>>> struct nlmsghdr* hdr = (struct nlmsghdr*)nlmsg.buf;
>> >>>> hdr->nlmsg_type = typ;
>> >>>> hdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK | flags;
>> >>>> memcpy(hdr + 1, data, size);
>> >>>> nlmsg.pos = (char*)(hdr + 1) + NLMSG_ALIGN(size);
>> >>>> }
>> >>>>
>> >>>> static void netlink_attr(int typ, const void* data, int size)
>> >>>> {
>> >>>> struct nlattr* attr = (struct nlattr*)nlmsg.pos;
>> >>>> attr->nla_len = sizeof(*attr) + size;
>> >>>> attr->nla_type = typ;
>> >>>> memcpy(attr + 1, data, size);
>> >>>> nlmsg.pos += NLMSG_ALIGN(attr->nla_len);
>> >>>> }
>> >>>>
>> >>>> static void netlink_nest(int typ)
>> >>>> {
>> >>>> struct nlattr* attr = (struct nlattr*)nlmsg.pos;
>> >>>> attr->nla_type = typ;
>> >>>> nlmsg.pos += sizeof(*attr);
>> >>>> nlmsg.nested[nlmsg.nesting++] = attr;
>> >>>> }
>> >>>>
>> >>>> static void netlink_done(void)
>> >>>> {
>> >>>> struct nlattr* attr = nlmsg.nested[--nlmsg.nesting];
>> >>>> attr->nla_len = nlmsg.pos - (char*)attr;
>> >>>> }
>> >>>>
>> >>>> static int netlink_send(int sock)
>> >>>> {
>> >>>> if (nlmsg.pos > nlmsg.buf + sizeof(nlmsg.buf) || nlmsg.nesting)
>> >>>> exit(1);
>> >>>> struct nlmsghdr* hdr = (struct nlmsghdr*)nlmsg.buf;
>> >>>> hdr->nlmsg_len = nlmsg.pos - nlmsg.buf;
>> >>>> struct sockaddr_nl addr;
>> >>>> memset(&addr, 0, sizeof(addr));
>> >>>> addr.nl_family = AF_NETLINK;
>> >>>> unsigned n = sendto(sock, nlmsg.buf, hdr->nlmsg_len, 0,
>> >>>> (struct sockaddr*)&addr, sizeof(addr));
>> >>>> if (n != hdr->nlmsg_len)
>> >>>> exit(1);
>> >>>> n = recv(sock, nlmsg.buf, sizeof(nlmsg.buf), 0);
>> >>>> if (n < sizeof(struct nlmsghdr) + sizeof(struct nlmsgerr))
>> >>>> exit(1);
>> >>>> if (hdr->nlmsg_type != NLMSG_ERROR)
>> >>>> exit(1);
>> >>>> return -((struct nlmsgerr*)(hdr + 1))->error;
>> >>>> }
>> >>>>
>> >>>> static void netlink_add_device_impl(const char* type, const char* name)
>> >>>> {
>> >>>> struct ifinfomsg hdr;
>> >>>> memset(&hdr, 0, sizeof(hdr));
>> >>>> netlink_init(RTM_NEWLINK, NLM_F_EXCL | NLM_F_CREATE, &hdr, sizeof(hdr));
>> >>>> if (name)
>> >>>> netlink_attr(IFLA_IFNAME, name, strlen(name));
>> >>>> netlink_nest(IFLA_LINKINFO);
>> >>>> netlink_attr(IFLA_INFO_KIND, type, strlen(type));
>> >>>> }
>> >>>>
>> >>>> static void netlink_add_device(int sock, const char* type, const char* name)
>> >>>> {
>> >>>> netlink_add_device_impl(type, name);
>> >>>> netlink_done();
>> >>>> int err = netlink_send(sock);
>> >>>> (void)err;
>> >>>> }
>> >>>>
>> >>>> static void netlink_add_veth(int sock, const char* name, const char* peer)
>> >>>> {
>> >>>> netlink_add_device_impl("veth", name);
>> >>>> netlink_nest(IFLA_INFO_DATA);
>> >>>> netlink_nest(VETH_INFO_PEER);
>> >>>> nlmsg.pos += sizeof(struct ifinfomsg);
>> >>>> netlink_attr(IFLA_IFNAME, peer, strlen(peer));
>> >>>> netlink_done();
>> >>>> netlink_done();
>> >>>> netlink_done();
>> >>>> int err = netlink_send(sock);
>> >>>> (void)err;
>> >>>> }
>> >>>>
>> >>>> static void netlink_add_hsr(int sock, const char* name, const char* slave1,
>> >>>> const char* slave2)
>> >>>> {
>> >>>> netlink_add_device_impl("hsr", name);
>> >>>> netlink_nest(IFLA_INFO_DATA);
>> >>>> int ifindex1 = if_nametoindex(slave1);
>> >>>> netlink_attr(IFLA_HSR_SLAVE1, &ifindex1, sizeof(ifindex1));
>> >>>> int ifindex2 = if_nametoindex(slave2);
>> >>>> netlink_attr(IFLA_HSR_SLAVE2, &ifindex2, sizeof(ifindex2));
>> >>>> netlink_done();
>> >>>> netlink_done();
>> >>>> int err = netlink_send(sock);
>> >>>> (void)err;
>> >>>> }
>> >>>>
>> >>>> static void netlink_device_change(int sock, const char* name, bool up,
>> >>>> const char* master, const void* mac,
>> >>>> int macsize)
>> >>>> {
>> >>>> struct ifinfomsg hdr;
>> >>>> memset(&hdr, 0, sizeof(hdr));
>> >>>> if (up)
>> >>>> hdr.ifi_flags = hdr.ifi_change = IFF_UP;
>> >>>> netlink_init(RTM_NEWLINK, 0, &hdr, sizeof(hdr));
>> >>>> netlink_attr(IFLA_IFNAME, name, strlen(name));
>> >>>> if (master) {
>> >>>> int ifindex = if_nametoindex(master);
>> >>>> netlink_attr(IFLA_MASTER, &ifindex, sizeof(ifindex));
>> >>>> }
>> >>>> if (macsize)
>> >>>> netlink_attr(IFLA_ADDRESS, mac, macsize);
>> >>>> int err = netlink_send(sock);
>> >>>> (void)err;
>> >>>> }
>> >>>>
>> >>>> static int netlink_add_addr(int sock, const char* dev, const void* addr,
>> >>>> int addrsize)
>> >>>> {
>> >>>> struct ifaddrmsg hdr;
>> >>>> memset(&hdr, 0, sizeof(hdr));
>> >>>> hdr.ifa_family = addrsize == 4 ? AF_INET : AF_INET6;
>> >>>> hdr.ifa_prefixlen = addrsize == 4 ? 24 : 120;
>> >>>> hdr.ifa_scope = RT_SCOPE_UNIVERSE;
>> >>>> hdr.ifa_index = if_nametoindex(dev);
>> >>>> netlink_init(RTM_NEWADDR, NLM_F_CREATE | NLM_F_REPLACE, &hdr,
>> >>>> sizeof(hdr));
>> >>>> netlink_attr(IFA_LOCAL, addr, addrsize);
>> >>>> netlink_attr(IFA_ADDRESS, addr, addrsize);
>> >>>> return netlink_send(sock);
>> >>>> }
>> >>>>
>> >>>> static void netlink_add_addr4(int sock, const char* dev, const char* addr)
>> >>>> {
>> >>>> struct in_addr in_addr;
>> >>>> inet_pton(AF_INET, addr, &in_addr);
>> >>>> int err = netlink_add_addr(sock, dev, &in_addr, sizeof(in_addr));
>> >>>> (void)err;
>> >>>> }
>> >>>>
>> >>>> static void netlink_add_addr6(int sock, const char* dev, const char* addr)
>> >>>> {
>> >>>> struct in6_addr in6_addr;
>> >>>> inet_pton(AF_INET6, addr, &in6_addr);
>> >>>> int err = netlink_add_addr(sock, dev, &in6_addr, sizeof(in6_addr));
>> >>>> (void)err;
>> >>>> }
>> >>>>
>> >>>> #define DEV_IPV4 "172.20.20.%d"
>> >>>> #define DEV_IPV6 "fe80::%02hx"
>> >>>> #define DEV_MAC 0x00aaaaaaaaaa
>> >>>> static void initialize_netdevices(void)
>> >>>> {
>> >>>> char netdevsim[16];
>> >>>> sprintf(netdevsim, "netdevsim%d", (int)procid);
>> >>>> struct {
>> >>>> const char* type;
>> >>>> const char* dev;
>> >>>> } devtypes[] = {
>> >>>> {"ip6gretap", "ip6gretap0"}, {"bridge", "bridge0"},
>> >>>> {"vcan", "vcan0"}, {"bond", "bond0"},
>> >>>> {"team", "team0"}, {"dummy", "dummy0"},
>> >>>> {"nlmon", "nlmon0"}, {"caif", "caif0"},
>> >>>> {"batadv", "batadv0"}, {"vxcan", "vxcan1"},
>> >>>> {"netdevsim", netdevsim}, {"veth", 0},
>> >>>> };
>> >>>> const char* devmasters[] = {"bridge", "bond", "team"};
>> >>>> struct {
>> >>>> const char* name;
>> >>>> int macsize;
>> >>>> bool noipv6;
>> >>>> } devices[] = {
>> >>>> {"lo", ETH_ALEN},
>> >>>> {"sit0", 0},
>> >>>> {"bridge0", ETH_ALEN},
>> >>>> {"vcan0", 0, true},
>> >>>> {"tunl0", 0},
>> >>>> {"gre0", 0},
>> >>>> {"gretap0", ETH_ALEN},
>> >>>> {"ip_vti0", 0},
>> >>>> {"ip6_vti0", 0},
>> >>>> {"ip6tnl0", 0},
>> >>>> {"ip6gre0", 0},
>> >>>> {"ip6gretap0", ETH_ALEN},
>> >>>> {"erspan0", ETH_ALEN},
>> >>>> {"bond0", ETH_ALEN},
>> >>>> {"veth0", ETH_ALEN},
>> >>>> {"veth1", ETH_ALEN},
>> >>>> {"team0", ETH_ALEN},
>> >>>> {"veth0_to_bridge", ETH_ALEN},
>> >>>> {"veth1_to_bridge", ETH_ALEN},
>> >>>> {"veth0_to_bond", ETH_ALEN},
>> >>>> {"veth1_to_bond", ETH_ALEN},
>> >>>> {"veth0_to_team", ETH_ALEN},
>> >>>> {"veth1_to_team", ETH_ALEN},
>> >>>> {"veth0_to_hsr", ETH_ALEN},
>> >>>> {"veth1_to_hsr", ETH_ALEN},
>> >>>> {"hsr0", 0},
>> >>>> {"dummy0", ETH_ALEN},
>> >>>> {"nlmon0", 0},
>> >>>> {"vxcan1", 0, true},
>> >>>> {"caif0", ETH_ALEN},
>> >>>> {"batadv0", ETH_ALEN},
>> >>>> {netdevsim, ETH_ALEN},
>> >>>> };
>> >>>> int sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
>> >>>> if (sock == -1)
>> >>>> exit(1);
>> >>>> unsigned i;
>> >>>> for (i = 0; i < sizeof(devtypes) / sizeof(devtypes[0]); i++)
>> >>>> netlink_add_device(sock, devtypes[i].type, devtypes[i].dev);
>> >>>> for (i = 0; i < sizeof(devmasters) / (sizeof(devmasters[0])); i++) {
>> >>>> char master[32], slave0[32], veth0[32], slave1[32], veth1[32];
>> >>>> sprintf(slave0, "%s_slave_0", devmasters[i]);
>> >>>> sprintf(veth0, "veth0_to_%s", devmasters[i]);
>> >>>> netlink_add_veth(sock, slave0, veth0);
>> >>>> sprintf(slave1, "%s_slave_1", devmasters[i]);
>> >>>> sprintf(veth1, "veth1_to_%s", devmasters[i]);
>> >>>> netlink_add_veth(sock, slave1, veth1);
>> >>>> sprintf(master, "%s0", devmasters[i]);
>> >>>> netlink_device_change(sock, slave0, false, master, 0, 0);
>> >>>> netlink_device_change(sock, slave1, false, master, 0, 0);
>> >>>> }
>> >>>> netlink_device_change(sock, "bridge_slave_0", true, 0, 0, 0);
>> >>>> netlink_device_change(sock, "bridge_slave_1", true, 0, 0, 0);
>> >>>> netlink_add_veth(sock, "hsr_slave_0", "veth0_to_hsr");
>> >>>> netlink_add_veth(sock, "hsr_slave_1", "veth1_to_hsr");
>> >>>> netlink_add_hsr(sock, "hsr0", "hsr_slave_0", "hsr_slave_1");
>> >>>> netlink_device_change(sock, "hsr_slave_0", true, 0, 0, 0);
>> >>>> netlink_device_change(sock, "hsr_slave_1", true, 0, 0, 0);
>> >>>> for (i = 0; i < sizeof(devices) / (sizeof(devices[0])); i++) {
>> >>>> char addr[32];
>> >>>> sprintf(addr, DEV_IPV4, i + 10);
>> >>>> netlink_add_addr4(sock, devices[i].name, addr);
>> >>>> if (!devices[i].noipv6) {
>> >>>> sprintf(addr, DEV_IPV6, i + 10);
>> >>>> netlink_add_addr6(sock, devices[i].name, addr);
>> >>>> }
>> >>>> uint64_t macaddr = DEV_MAC + ((i + 10ull) << 40);
>> >>>> netlink_device_change(sock, devices[i].name, true, 0, &macaddr,
>> >>>> devices[i].macsize);
>> >>>> }
>> >>>> close(sock);
>> >>>> }
>> >>>> static void initialize_netdevices_init(void)
>> >>>> {
>> >>>> int sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
>> >>>> if (sock == -1)
>> >>>> exit(1);
>> >>>> struct {
>> >>>> const char* type;
>> >>>> int macsize;
>> >>>> bool noipv6;
>> >>>> bool noup;
>> >>>> } devtypes[] = {
>> >>>> {"nr", 7, true}, {"rose", 5, true, true},
>> >>>> };
>> >>>> unsigned i;
>> >>>> for (i = 0; i < sizeof(devtypes) / sizeof(devtypes[0]); i++) {
>> >>>> char dev[32], addr[32];
>> >>>> sprintf(dev, "%s%d", devtypes[i].type, (int)procid);
>> >>>> sprintf(addr, "172.30.%d.%d", i, (int)procid + 1);
>> >>>> netlink_add_addr4(sock, dev, addr);
>> >>>> if (!devtypes[i].noipv6) {
>> >>>> sprintf(addr, "fe88::%02hx:%02hx", i, (int)procid + 1);
>> >>>> netlink_add_addr6(sock, dev, addr);
>> >>>> }
>> >>>> int macsize = devtypes[i].macsize;
>> >>>> uint64_t macaddr = 0xbbbbbb +
>> >>>> ((unsigned long long)i << (8 * (macsize - 2))) +
>> >>>> (procid << (8 * (macsize - 1)));
>> >>>> netlink_device_change(sock, dev, !devtypes[i].noup, 0, &macaddr,
>> >>>> macsize);
>> >>>> }
>> >>>> close(sock);
>> >>>> }
>> >>>>
>> >>>> static void setup_common()
>> >>>> {
>> >>>> if (mount(0, "/sys/fs/fuse/connections", "fusectl", 0, 0)) {
>> >>>> }
>> >>>> }
>> >>>>
>> >>>> static void loop();
>> >>>>
>> >>>> static void sandbox_common()
>> >>>> {
>> >>>> prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
>> >>>> setpgrp();
>> >>>> setsid();
>> >>>> struct rlimit rlim;
>> >>>> rlim.rlim_cur = rlim.rlim_max = 200 << 20;
>> >>>> setrlimit(RLIMIT_AS, &rlim);
>> >>>> rlim.rlim_cur = rlim.rlim_max = 32 << 20;
>> >>>> setrlimit(RLIMIT_MEMLOCK, &rlim);
>> >>>> rlim.rlim_cur = rlim.rlim_max = 136 << 20;
>> >>>> setrlimit(RLIMIT_FSIZE, &rlim);
>> >>>> rlim.rlim_cur = rlim.rlim_max = 1 << 20;
>> >>>> setrlimit(RLIMIT_STACK, &rlim);
>> >>>> rlim.rlim_cur = rlim.rlim_max = 0;
>> >>>> setrlimit(RLIMIT_CORE, &rlim);
>> >>>> rlim.rlim_cur = rlim.rlim_max = 256;
>> >>>> setrlimit(RLIMIT_NOFILE, &rlim);
>> >>>> if (unshare(CLONE_NEWNS)) {
>> >>>> }
>> >>>> if (unshare(CLONE_NEWIPC)) {
>> >>>> }
>> >>>> if (unshare(0x02000000)) {
>> >>>> }
>> >>>> if (unshare(CLONE_NEWUTS)) {
>> >>>> }
>> >>>> if (unshare(CLONE_SYSVSEM)) {
>> >>>> }
>> >>>> typedef struct {
>> >>>> const char* name;
>> >>>> const char* value;
>> >>>> } sysctl_t;
>> >>>> static const sysctl_t sysctls[] = {
>> >>>> {"/proc/sys/kernel/shmmax", "16777216"},
>> >>>> {"/proc/sys/kernel/shmall", "536870912"},
>> >>>> {"/proc/sys/kernel/shmmni", "1024"},
>> >>>> {"/proc/sys/kernel/msgmax", "8192"},
>> >>>> {"/proc/sys/kernel/msgmni", "1024"},
>> >>>> {"/proc/sys/kernel/msgmnb", "1024"},
>> >>>> {"/proc/sys/kernel/sem", "1024 1048576 500 1024"},
>> >>>> };
>> >>>> unsigned i;
>> >>>> for (i = 0; i < sizeof(sysctls) / sizeof(sysctls[0]); i++)
>> >>>> write_file(sysctls[i].name, sysctls[i].value);
>> >>>> }
>> >>>>
>> >>>> int wait_for_loop(int pid)
>> >>>> {
>> >>>> if (pid < 0)
>> >>>> exit(1);
>> >>>> int status = 0;
>> >>>> while (waitpid(-1, &status, __WALL) != pid) {
>> >>>> }
>> >>>> return WEXITSTATUS(status);
>> >>>> }
>> >>>>
>> >>>> static int do_sandbox_none(void)
>> >>>> {
>> >>>> if (unshare(CLONE_NEWPID)) {
>> >>>> }
>> >>>> int pid = fork();
>> >>>> if (pid != 0)
>> >>>> return wait_for_loop(pid);
>> >>>> setup_common();
>> >>>> sandbox_common();
>> >>>> initialize_netdevices_init();
>> >>>> if (unshare(CLONE_NEWNET)) {
>> >>>> }
>> >>>> initialize_netdevices();
>> >>>> loop();
>> >>>> exit(1);
>> >>>> }
>> >>>>
>> >>>> #define FS_IOC_SETFLAGS _IOW('f', 2, long)
>> >>>> static void remove_dir(const char* dir)
>> >>>> {
>> >>>> DIR* dp;
>> >>>> struct dirent* ep;
>> >>>> int iter = 0;
>> >>>> retry:
>> >>>> while (umount2(dir, MNT_DETACH) == 0) {
>> >>>> }
>> >>>> dp = opendir(dir);
>> >>>> if (dp == NULL) {
>> >>>> if (errno == EMFILE) {
>> >>>> exit(1);
>> >>>> }
>> >>>> exit(1);
>> >>>> }
>> >>>> while ((ep = readdir(dp))) {
>> >>>> if (strcmp(ep->d_name, ".") == 0 || strcmp(ep->d_name, "..") == 0)
>> >>>> continue;
>> >>>> char filename[FILENAME_MAX];
>> >>>> snprintf(filename, sizeof(filename), "%s/%s", dir, ep->d_name);
>> >>>> while (umount2(filename, MNT_DETACH) == 0) {
>> >>>> }
>> >>>> struct stat st;
>> >>>> if (lstat(filename, &st))
>> >>>> exit(1);
>> >>>> if (S_ISDIR(st.st_mode)) {
>> >>>> remove_dir(filename);
>> >>>> continue;
>> >>>> }
>> >>>> int i;
>> >>>> for (i = 0;; i++) {
>> >>>> if (unlink(filename) == 0)
>> >>>> break;
>> >>>> if (errno == EPERM) {
>> >>>> int fd = open(filename, O_RDONLY);
>> >>>> if (fd != -1) {
>> >>>> long flags = 0;
>> >>>> if (ioctl(fd, FS_IOC_SETFLAGS, &flags) == 0)
>> >>>> close(fd);
>> >>>> continue;
>> >>>> }
>> >>>> }
>> >>>> if (errno == EROFS) {
>> >>>> break;
>> >>>> }
>> >>>> if (errno != EBUSY || i > 100)
>> >>>> exit(1);
>> >>>> if (umount2(filename, MNT_DETACH))
>> >>>> exit(1);
>> >>>> }
>> >>>> }
>> >>>> closedir(dp);
>> >>>> int i;
>> >>>> for (i = 0;; i++) {
>> >>>> if (rmdir(dir) == 0)
>> >>>> break;
>> >>>> if (i < 100) {
>> >>>> if (errno == EPERM) {
>> >>>> int fd = open(dir, O_RDONLY);
>> >>>> if (fd != -1) {
>> >>>> long flags = 0;
>> >>>> if (ioctl(fd, FS_IOC_SETFLAGS, &flags) == 0)
>> >>>> close(fd);
>> >>>> continue;
>> >>>> }
>> >>>> }
>> >>>> if (errno == EROFS) {
>> >>>> break;
>> >>>> }
>> >>>> if (errno == EBUSY) {
>> >>>> if (umount2(dir, MNT_DETACH))
>> >>>> exit(1);
>> >>>> continue;
>> >>>> }
>> >>>> if (errno == ENOTEMPTY) {
>> >>>> if (iter < 100) {
>> >>>> iter++;
>> >>>> goto retry;
>> >>>> }
>> >>>> }
>> >>>> }
>> >>>> exit(1);
>> >>>> }
>> >>>> }
>> >>>>
>> >>>> static void kill_and_wait(int pid, int* status)
>> >>>> {
>> >>>> kill(-pid, SIGKILL);
>> >>>> kill(pid, SIGKILL);
>> >>>> int i;
>> >>>> for (i = 0; i < 100; i++) {
>> >>>> if (waitpid(-1, status, WNOHANG | __WALL) == pid)
>> >>>> return;
>> >>>> usleep(1000);
>> >>>> }
>> >>>> DIR* dir = opendir("/sys/fs/fuse/connections");
>> >>>> if (dir) {
>> >>>> for (;;) {
>> >>>> struct dirent* ent = readdir(dir);
>> >>>> if (!ent)
>> >>>> break;
>> >>>> if (strcmp(ent->d_name, ".") == 0 || strcmp(ent->d_name, "..") == 0)
>> >>>> continue;
>> >>>> char abort[300];
>> >>>> snprintf(abort, sizeof(abort), "/sys/fs/fuse/connections/%s/abort",
>> >>>> ent->d_name);
>> >>>> int fd = open(abort, O_WRONLY);
>> >>>> if (fd == -1) {
>> >>>> continue;
>> >>>> }
>> >>>> if (write(fd, abort, 1) < 0) {
>> >>>> }
>> >>>> close(fd);
>> >>>> }
>> >>>> closedir(dir);
>> >>>> } else {
>> >>>> }
>> >>>> while (waitpid(-1, status, __WALL) != pid) {
>> >>>> }
>> >>>> }
>> >>>>
>> >>>> #define SYZ_HAVE_SETUP_TEST 1
>> >>>> static void setup_test()
>> >>>> {
>> >>>> prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
>> >>>> setpgrp();
>> >>>> }
>> >>>>
>> >>>> #define SYZ_HAVE_RESET_TEST 1
>> >>>> static void reset_test()
>> >>>> {
>> >>>> int fd;
>> >>>> for (fd = 3; fd < 30; fd++)
>> >>>> close(fd);
>> >>>> }
>> >>>>
>> >>>> static void execute_one(void);
>> >>>>
>> >>>> #define WAIT_FLAGS __WALL
>> >>>>
>> >>>> static void loop(void)
>> >>>> {
>> >>>> int iter;
>> >>>> for (iter = 0;; iter++) {
>> >>>> char cwdbuf[32];
>> >>>> sprintf(cwdbuf, "./%d", iter);
>> >>>> if (mkdir(cwdbuf, 0777))
>> >>>> exit(1);
>> >>>> int pid = fork();
>> >>>> if (pid < 0)
>> >>>> exit(1);
>> >>>> if (pid == 0) {
>> >>>> if (chdir(cwdbuf))
>> >>>> exit(1);
>> >>>> setup_test();
>> >>>> execute_one();
>> >>>> reset_test();
>> >>>> exit(0);
>> >>>> }
>> >>>> int status = 0;
>> >>>> uint64_t start = current_time_ms();
>> >>>> for (;;) {
>> >>>> if (waitpid(-1, &status, WNOHANG | WAIT_FLAGS) == pid)
>> >>>> break;
>> >>>> sleep_ms(1);
>> >>>> if (current_time_ms() - start < 5 * 1000)
>> >>>> continue;
>> >>>> kill_and_wait(pid, &status);
>> >>>> break;
>> >>>> }
>> >>>> remove_dir(cwdbuf);
>> >>>> }
>> >>>> }
>> >>>>
>> >>>> void execute_one(void)
>> >>>> {
>> >>>> syscall(__NR_unshare, 0x40000000);
>> >>>> }
>> >>>> int main(void)
>> >>>> {
>> >>>> syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0);
>> >>>> for (procid = 0; procid < 8; procid++) {
>> >>>> if (fork() == 0) {
>> >>>> use_temporary_dir();
>> >>>> do_sandbox_none();
>> >>>> }
>> >>>> }
>> >>>> sleep(1000000);
>> >>>> return 0;
>> >>>> }
>> >>>>
>> >>>>
>> >>>> I reviewed kernel code and found a bug that
>> >>>> net_drop_ns func doesn't call net_free func when refcount_dec_and_test's
>> >>>> return value is zero.
>> >>> Yes. We don't call net_free when the reference count does not decrement
>> >>> to zero. The reference count is initialized to 1 a few lines above the
>> >>> section of code in your patch so that should not be a problem.
>> >>>
>> >>>> or
>> >>>> when rv = down_read_killable(&pernet_ops_rwsem) < 0, it doesn't need to
>> >>>> call refcount_dec_and_test.
>> >>> It doesn't need to but it should be harmless.
>> >>>
>> >>>> https://github.com/torvalds/linux/commit/5ba049a5cc8e24a1643df75bbf65b4efa070fa74#diff-9312644e2968a45510bacdd2b2872ad2
>> >>>> (I can't reproduce this bug on v4.15 , and
>> >>>> 1bdbe227492075d058e37cb3d400e6468d0095b5 with my patch. Because of the
>> >>>> previous version of kernel doesn't have this bug.)
>> >>>> This bug can lead to memory leak or DOS.
>> >>>>
>> >>>> I made a patch for this bug. (just revert to a before commit)
>> >>> What am I missing?
>> >>>
>> >>> The only thing I can see your patch doing is covering up a memory stomp
>> >>> that has the effect of changing the value of net->passive. I am not
>> >>> really keen on hiding bugs of that kind.
>> >>>
>> >>>
>> >>>> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
>> >>>> index b02fb19df2cc..9de0ade14956 100644
>> >>>> --- a/net/core/net_namespace.c
>> >>>> +++ b/net/core/net_namespace.c
>> >>>> @@ -431,15 +431,18 @@ struct net *copy_net_ns(unsigned long flags,
>> >>>> get_user_ns(user_ns);
>> >>>>
>> >>>> rv = down_read_killable(&pernet_ops_rwsem);
>> >>>> - if (rv < 0)
>> >>>> - goto put_userns;
>> >>>> + if (rv < 0){
>> >>>> + net_free(net);
>> >>>> + dec_net_namespaces(ucounts);
>> >>>> + put_user_ns(user_ns);
>> >>>> + return ERR_PTR(rv);
>> >>>> + }
>> >>>>
>> >>>> rv = setup_net(net, user_ns);
>> >>>>
>> >>>> up_read(&pernet_ops_rwsem);
>> >>>>
>> >>>> if (rv < 0) {
>> >>>> -put_userns:
>> >>>> put_user_ns(user_ns);
>> >>>> net_drop_ns(net);
>> >>>> dec_ucounts:
>> >>>>
>> >>>> and, sorry for my encrypted mails.
>> >>> Eric
>> >>>
>
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