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Message-ID: <cdb5f0c9-1ad9-dd9d-b24d-e127928ada98@gmail.com>
Date: Mon, 9 Aug 2021 22:22:47 +0300
From: Pavel Skripkin <paskripkin@...il.com>
To: syzbot <syzbot+649e339fa6658ee623d3@...kaller.appspotmail.com>,
coreteam@...filter.org, davem@...emloft.net, fw@...len.de,
kadlec@...filter.org, kuba@...nel.org,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
netfilter-devel@...r.kernel.org, pablo@...filter.org,
syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] KASAN: use-after-free Write in nft_ct_tmpl_put_pcpu
On 8/7/21 4:44 PM, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 894d6f401b21 Merge tag 'spi-fix-v5.14-rc4' of git://git.ke..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17c622fa300000
> kernel config: https://syzkaller.appspot.com/x/.config?x=343fd21f6f4da2d6
> dashboard link: https://syzkaller.appspot.com/bug?extid=649e339fa6658ee623d3
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=110319aa300000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1142fac9d00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+649e339fa6658ee623d3@...kaller.appspotmail.com
>
> ==================================================================
> BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
> BUG: KASAN: use-after-free in atomic_dec_and_test include/asm-generic/atomic-instrumented.h:542 [inline]
> BUG: KASAN: use-after-free in nf_conntrack_put include/linux/netfilter/nf_conntrack_common.h:33 [inline]
> BUG: KASAN: use-after-free in nf_ct_put include/net/netfilter/nf_conntrack.h:176 [inline]
> BUG: KASAN: use-after-free in nft_ct_tmpl_put_pcpu+0x135/0x1e0 net/netfilter/nft_ct.c:356
> Write of size 4 at addr ffff88803d750400 by task syz-executor409/9789
>
> CPU: 0 PID: 9789 Comm: syz-executor409 Not tainted 5.14.0-rc4-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
> __dump_stack lib/dump_stack.c:88 [inline]
> dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
> print_address_description.constprop.0.cold+0x6c/0x309 mm/kasan/report.c:233
> __kasan_report mm/kasan/report.c:419 [inline]
> kasan_report.cold+0x83/0xdf mm/kasan/report.c:436
> check_region_inline mm/kasan/generic.c:183 [inline]
> kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
> instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
> atomic_dec_and_test include/asm-generic/atomic-instrumented.h:542 [inline]
> nf_conntrack_put include/linux/netfilter/nf_conntrack_common.h:33 [inline]
> nf_ct_put include/net/netfilter/nf_conntrack.h:176 [inline]
> nft_ct_tmpl_put_pcpu+0x135/0x1e0 net/netfilter/nft_ct.c:356
(*)
> __nft_ct_set_destroy net/netfilter/nft_ct.c:529 [inline]
> __nft_ct_set_destroy net/netfilter/nft_ct.c:518 [inline]
> nft_ct_set_init+0x41e/0x750 net/netfilter/nft_ct.c:614
> nf_tables_newexpr net/netfilter/nf_tables_api.c:2742 [inline]
> nft_expr_init+0x145/0x2d0 net/netfilter/nf_tables_api.c:2780
> nft_set_elem_expr_alloc+0x27/0x280 net/netfilter/nf_tables_api.c:5284
> nf_tables_newset+0x208a/0x32f0 net/netfilter/nf_tables_api.c:4389
> nfnetlink_rcv_batch+0x1710/0x25f0 net/netfilter/nfnetlink.c:513
> nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline]
> nfnetlink_rcv+0x3af/0x420 net/netfilter/nfnetlink.c:652
> netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
> netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340
> netlink_sendmsg+0x86d/0xdb0 net/netlink/af_netlink.c:1929
> sock_sendmsg_nosec net/socket.c:703 [inline]
> sock_sendmsg+0xcf/0x120 net/socket.c:723
> ____sys_sendmsg+0x6e8/0x810 net/socket.c:2392
> ___sys_sendmsg+0xf3/0x170 net/socket.c:2446
> __sys_sendmsg+0xe5/0x1b0 net/socket.c:2475
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x444819
[snip]
> Freed by task 9788:
> kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
> kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
> kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:360
> ____kasan_slab_free mm/kasan/common.c:366 [inline]
> ____kasan_slab_free mm/kasan/common.c:328 [inline]
> __kasan_slab_free+0xfb/0x130 mm/kasan/common.c:374
> kasan_slab_free include/linux/kasan.h:230 [inline]
> slab_free_hook mm/slub.c:1625 [inline]
> slab_free_freelist_hook+0xdf/0x240 mm/slub.c:1650
> slab_free mm/slub.c:3210 [inline]
> kfree+0xe4/0x530 mm/slub.c:4264
> nf_ct_tmpl_free net/netfilter/nf_conntrack_core.c:590 [inline]
> destroy_conntrack+0x222/0x2c0 net/netfilter/nf_conntrack_core.c:613
> nf_conntrack_destroy+0xab/0x230 net/netfilter/core.c:677
> nf_conntrack_put include/linux/netfilter/nf_conntrack_common.h:34 [inline]
> nf_ct_put include/net/netfilter/nf_conntrack.h:176 [inline]
> nft_ct_tmpl_put_pcpu+0x15e/0x1e0 net/netfilter/nft_ct.c:356
I think, there a missing lock in this function:
for_each_possible_cpu(cpu) {
ct = per_cpu(nft_ct_pcpu_template, cpu);
if (!ct)
break;
nf_ct_put(ct);
per_cpu(nft_ct_pcpu_template, cpu) = NULL;
}
Syzbot hit a UAF in nft_ct_tmpl_put_pcpu() (*), but freed template
should be NULL.
So I suspect following scenario:
CPU0: CPU1:
= per_cpu()
= per_cpu()
nf_ct_put
per_cpu = NULL
nf_ct_put()
* UAF *
#syz test
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
With regards,
Pavel Skripkin
> __nft_ct_set_destroy net/netfilter/nft_ct.c:529 [inline]
> __nft_ct_set_destroy net/netfilter/nft_ct.c:518 [inline]
> nft_ct_set_init+0x41e/0x750 net/netfilter/nft_ct.c:614
> nf_tables_newexpr net/netfilter/nf_tables_api.c:2742 [inline]
> nft_expr_init+0x145/0x2d0 net/netfilter/nf_tables_api.c:2780
> nft_set_elem_expr_alloc+0x27/0x280 net/netfilter/nf_tables_api.c:5284
> nf_tables_newset+0x208a/0x32f0 net/netfilter/nf_tables_api.c:4389
> nfnetlink_rcv_batch+0x1710/0x25f0 net/netfilter/nfnetlink.c:513
> nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline]
> nfnetlink_rcv+0x3af/0x420 net/netfilter/nfnetlink.c:652
> netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
> netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340
> netlink_sendmsg+0x86d/0xdb0 net/netlink/af_netlink.c:1929
> sock_sendmsg_nosec net/socket.c:703 [inline]
> sock_sendmsg+0xcf/0x120 net/socket.c:723
> ____sys_sendmsg+0x6e8/0x810 net/socket.c:2392
> ___sys_sendmsg+0xf3/0x170 net/socket.c:2446
> __sys_sendmsg+0xe5/0x1b0 net/socket.c:2475
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> The buggy address belongs to the object at ffff88803d750400
> which belongs to the cache kmalloc-512 of size 512
> The buggy address is located 0 bytes inside of
> 512-byte region [ffff88803d750400, ffff88803d750600)
> The buggy address belongs to the page:
> page:ffffea0000f5d400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3d750
> head:ffffea0000f5d400 order:2 compound_mapcount:0 compound_pincount:0
> flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
> raw: 00fff00000010200 0000000000000000 dead000000000122 ffff888010841c80
> raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> page_owner tracks the page as allocated
> page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 9789, ts 226704064982, free_ts 0
> prep_new_page mm/page_alloc.c:2436 [inline]
> get_page_from_freelist+0xa72/0x2f80 mm/page_alloc.c:4169
> __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5391
> alloc_pages+0x18c/0x2a0 mm/mempolicy.c:2244
> alloc_slab_page mm/slub.c:1688 [inline]
> allocate_slab+0x32e/0x4b0 mm/slub.c:1828
> new_slab mm/slub.c:1891 [inline]
> new_slab_objects mm/slub.c:2637 [inline]
> ___slab_alloc+0x4ba/0x820 mm/slub.c:2800
> __slab_alloc.constprop.0+0xa7/0xf0 mm/slub.c:2840
> slab_alloc_node mm/slub.c:2922 [inline]
> slab_alloc mm/slub.c:2964 [inline]
> kmem_cache_alloc_trace+0x30f/0x3c0 mm/slub.c:2981
> kmalloc include/linux/slab.h:591 [inline]
> kzalloc include/linux/slab.h:721 [inline]
> nf_ct_tmpl_alloc+0x8d/0x270 net/netfilter/nf_conntrack_core.c:569
> nft_ct_tmpl_alloc_pcpu net/netfilter/nft_ct.c:371 [inline]
> nft_ct_set_init+0x4d6/0x750 net/netfilter/nft_ct.c:567
> nf_tables_newexpr net/netfilter/nf_tables_api.c:2742 [inline]
> nft_expr_init+0x145/0x2d0 net/netfilter/nf_tables_api.c:2780
> nft_set_elem_expr_alloc+0x27/0x280 net/netfilter/nf_tables_api.c:5284
> nf_tables_newset+0x208a/0x32f0 net/netfilter/nf_tables_api.c:4389
> nfnetlink_rcv_batch+0x1710/0x25f0 net/netfilter/nfnetlink.c:513
> nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline]
> nfnetlink_rcv+0x3af/0x420 net/netfilter/nfnetlink.c:652
> netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
> netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340
> netlink_sendmsg+0x86d/0xdb0 net/netlink/af_netlink.c:1929
> page_owner free stack trace missing
>
> Memory state around the buggy address:
> ffff88803d750300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff88803d750380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>ffff88803d750400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff88803d750480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88803d750500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
View attachment "0001-netfilter-add-mutex-to-protect-nft_ct_pcpu_template.patch" of type "text/x-patch" (2543 bytes)
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