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SMTP id h21mr18616628lfu.543.1628536970060; Mon, 09 Aug 2021 12:22:50 -0700 (PDT) Received: from [192.168.1.11] ([46.235.67.232]) by smtp.gmail.com with ESMTPSA id h9sm1243524ljq.92.2021.08.09.12.22.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 09 Aug 2021 12:22:49 -0700 (PDT) Subject: Re: [syzbot] KASAN: use-after-free Write in nft_ct_tmpl_put_pcpu To: syzbot , coreteam@netfilter.org, davem@davemloft.net, fw@strlen.de, kadlec@netfilter.org, kuba@kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, netfilter-devel@vger.kernel.org, pablo@netfilter.org, syzkaller-bugs@googlegroups.com References: <000000000000b720b705c8f8599f@google.com> From: Pavel Skripkin Message-ID: Date: Mon, 9 Aug 2021 22:22:47 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <000000000000b720b705c8f8599f@google.com> Content-Type: multipart/mixed; boundary="------------B2B9016DCAFA275198E2C6CE" Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a multi-part message in MIME format. --------------B2B9016DCAFA275198E2C6CE Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit 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@syzkaller.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 > ================================================================== > --------------B2B9016DCAFA275198E2C6CE Content-Type: text/x-patch; charset=UTF-8; name="0001-netfilter-add-mutex-to-protect-nft_ct_pcpu_template.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename*0="0001-netfilter-add-mutex-to-protect-nft_ct_pcpu_template.pat"; filename*1="ch" >From 39275bfc1bac5758752ba2bf4df68e244590589b Mon Sep 17 00:00:00 2001 From: Pavel Skripkin Date: Mon, 9 Aug 2021 22:13:44 +0300 Subject: [PATCH] netfilter: add mutex to protect nft_ct_pcpu_template /* ... */ Signed-off-by: Pavel Skripkin --- net/netfilter/nft_ct.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/net/netfilter/nft_ct.c b/net/netfilter/nft_ct.c index 337e22d8b40b..09f03036e5c8 100644 --- a/net/netfilter/nft_ct.c +++ b/net/netfilter/nft_ct.c @@ -10,6 +10,7 @@ #include #include #include +#include #include #include #include @@ -41,6 +42,7 @@ struct nft_ct_helper_obj { #ifdef CONFIG_NF_CONNTRACK_ZONES static DEFINE_PER_CPU(struct nf_conn *, nft_ct_pcpu_template); static unsigned int nft_ct_pcpu_template_refcnt __read_mostly; +static DEFINE_MUTEX(nft_ct_pcpu_template_mutex); #endif static u64 nft_ct_get_eval_counter(const struct nf_conn_counter *c, @@ -344,11 +346,13 @@ static const struct nla_policy nft_ct_policy[NFTA_CT_MAX + 1] = { }; #ifdef CONFIG_NF_CONNTRACK_ZONES -static void nft_ct_tmpl_put_pcpu(void) +static void nft_ct_tmpl_put_pcpu(bool lock) { struct nf_conn *ct; int cpu; + if (lock) + mutex_lock(&nft_ct_pcpu_template_mutex); for_each_possible_cpu(cpu) { ct = per_cpu(nft_ct_pcpu_template, cpu); if (!ct) @@ -356,6 +360,8 @@ static void nft_ct_tmpl_put_pcpu(void) nf_ct_put(ct); per_cpu(nft_ct_pcpu_template, cpu) = NULL; } + if (lock) + mutex_unlock(&nft_ct_pcpu_template_mutex); } static bool nft_ct_tmpl_alloc_pcpu(void) @@ -367,16 +373,18 @@ static bool nft_ct_tmpl_alloc_pcpu(void) if (nft_ct_pcpu_template_refcnt) return true; + mutex_lock(&nft_ct_pcpu_template_mutex); for_each_possible_cpu(cpu) { tmp = nf_ct_tmpl_alloc(&init_net, &zone, GFP_KERNEL); if (!tmp) { - nft_ct_tmpl_put_pcpu(); + nft_ct_tmpl_put_pcpu(false); return false; } atomic_set(&tmp->ct_general.use, 1); per_cpu(nft_ct_pcpu_template, cpu) = tmp; } + mutex_unlock(&nft_ct_pcpu_template_mutex); return true; } @@ -526,7 +534,7 @@ static void __nft_ct_set_destroy(const struct nft_ctx *ctx, struct nft_ct *priv) #ifdef CONFIG_NF_CONNTRACK_ZONES case NFT_CT_ZONE: if (--nft_ct_pcpu_template_refcnt == 0) - nft_ct_tmpl_put_pcpu(); + nft_ct_tmpl_put_pcpu(true); break; #endif default: -- 2.32.0 --------------B2B9016DCAFA275198E2C6CE--