Re: net/ipv6: use-after-free in sock_wfree

From: Eric Dumazet
Date: Mon Jan 09 2017 - 12:21:54 EST

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On Mon, Jan 9, 2017 at 9:11 AM, Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
> On Mon, Jan 9, 2017 at 6:08 PM, Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
>> Hi!
>>
>> I've got the following error report while running the syzkaller fuzzer.
>>
>> On commit a121103c922847ba5010819a3f250f1f7fc84ab8 (4.10-rc3).
>>
>> A reproducer is attached.
>>
>> ==================================================================
>> BUG: KASAN: use-after-free in sock_wfree+0x118/0x120
>> Read of size 8 at addr ffff880062da0060 by task a.out/4140
>>
>> page:ffffea00018b6800 count:1 mapcount:0 mapping: (null)
>> index:0x0 compound_mapcount: 0
>> flags: 0x100000000008100(slab|head)
>> raw: 0100000000008100 0000000000000000 0000000000000000 0000000180130013
>> raw: dead000000000100 dead000000000200 ffff88006741f140 0000000000000000
>> page dumped because: kasan: bad access detected
>>
>> CPU: 0 PID: 4140 Comm: a.out Not tainted 4.10.0-rc3+ #59
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>> Call Trace:
>> __dump_stack lib/dump_stack.c:15
>> dump_stack+0x292/0x398 lib/dump_stack.c:51
>> describe_address mm/kasan/report.c:262
>> kasan_report_error+0x121/0x560 mm/kasan/report.c:370
>> kasan_report mm/kasan/report.c:392
>> __asan_report_load8_noabort+0x3e/0x40 mm/kasan/report.c:413
>> sock_flag ./arch/x86/include/asm/bitops.h:324
>> sock_wfree+0x118/0x120 net/core/sock.c:1631
>> skb_release_head_state+0xfc/0x250 net/core/skbuff.c:655
>> skb_release_all+0x15/0x60 net/core/skbuff.c:668
>> __kfree_skb+0x15/0x20 net/core/skbuff.c:684
>> kfree_skb+0x16e/0x4e0 net/core/skbuff.c:705
>> inet_frag_destroy+0x121/0x290 net/ipv4/inet_fragment.c:304
>> inet_frag_put ./include/net/inet_frag.h:133
>> nf_ct_frag6_gather+0x1125/0x38b0 net/ipv6/netfilter/nf_conntrack_reasm.c:617
>> ipv6_defrag+0x21b/0x350 net/ipv6/netfilter/nf_defrag_ipv6_hooks.c:68
>> nf_hook_entry_hookfn ./include/linux/netfilter.h:102
>> nf_hook_slow+0xc3/0x290 net/netfilter/core.c:310
>> nf_hook ./include/linux/netfilter.h:212
>> __ip6_local_out+0x52c/0xaf0 net/ipv6/output_core.c:160
>> ip6_local_out+0x2d/0x170 net/ipv6/output_core.c:170
>> ip6_send_skb+0xa1/0x340 net/ipv6/ip6_output.c:1722
>> ip6_push_pending_frames+0xb3/0xe0 net/ipv6/ip6_output.c:1742
>> rawv6_push_pending_frames net/ipv6/raw.c:613
>> rawv6_sendmsg+0x2cff/0x4130 net/ipv6/raw.c:927
>> inet_sendmsg+0x164/0x5b0 net/ipv4/af_inet.c:744
>> sock_sendmsg_nosec net/socket.c:635
>> sock_sendmsg+0xca/0x110 net/socket.c:645
>> sock_write_iter+0x326/0x620 net/socket.c:848
>> new_sync_write fs/read_write.c:499
>> __vfs_write+0x483/0x760 fs/read_write.c:512
>> vfs_write+0x187/0x530 fs/read_write.c:560
>> SYSC_write fs/read_write.c:607
>> SyS_write+0xfb/0x230 fs/read_write.c:599
>> entry_SYSCALL_64_fastpath+0x1f/0xc2 arch/x86/entry/entry_64.S:203
>> RIP: 0033:0x7ff26e6f5b79
>> RSP: 002b:00007ff268e0ed98 EFLAGS: 00000206 ORIG_RAX: 0000000000000001
>> RAX: ffffffffffffffda RBX: 00007ff268e0f9c0 RCX: 00007ff26e6f5b79
>> RDX: 0000000000000010 RSI: 0000000020f50fe1 RDI: 0000000000000003
>> RBP: 00007ff26ebc1220 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
>> R13: 00007ff268e0f9c0 R14: 00007ff26efec040 R15: 0000000000000003
>>
>> The buggy address belongs to the object at ffff880062da0000
>> which belongs to the cache RAWv6 of size 1504
>> The buggy address ffff880062da0060 is located 96 bytes inside
>> of 1504-byte region [ffff880062da0000, ffff880062da05e0)
>>
>> Freed by task 4113:
>> save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
>> save_stack+0x43/0xd0 mm/kasan/kasan.c:502
>> set_track mm/kasan/kasan.c:514
>> kasan_slab_free+0x73/0xc0 mm/kasan/kasan.c:578
>> slab_free_hook mm/slub.c:1352
>> slab_free_freelist_hook mm/slub.c:1374
>> slab_free mm/slub.c:2951
>> kmem_cache_free+0xb2/0x2c0 mm/slub.c:2973
>> sk_prot_free net/core/sock.c:1377
>> __sk_destruct+0x49c/0x6e0 net/core/sock.c:1452
>> sk_destruct+0x47/0x80 net/core/sock.c:1460
>> __sk_free+0x57/0x230 net/core/sock.c:1468
>> sk_free+0x23/0x30 net/core/sock.c:1479
>> sock_put ./include/net/sock.h:1638
>> sk_common_release+0x31e/0x4e0 net/core/sock.c:2782
>> rawv6_close+0x54/0x80 net/ipv6/raw.c:1214
>> inet_release+0xed/0x1c0 net/ipv4/af_inet.c:425
>> inet6_release+0x50/0x70 net/ipv6/af_inet6.c:431
>> sock_release+0x8d/0x1e0 net/socket.c:599
>> sock_close+0x16/0x20 net/socket.c:1063
>> __fput+0x332/0x7f0 fs/file_table.c:208
>> ____fput+0x15/0x20 fs/file_table.c:244
>> task_work_run+0x19b/0x270 kernel/task_work.c:116
>> exit_task_work ./include/linux/task_work.h:21
>> do_exit+0x186b/0x2800 kernel/exit.c:839
>> do_group_exit+0x149/0x420 kernel/exit.c:943
>> SYSC_exit_group kernel/exit.c:954
>> SyS_exit_group+0x1d/0x20 kernel/exit.c:952
>> entry_SYSCALL_64_fastpath+0x1f/0xc2 arch/x86/entry/entry_64.S:203
>>
>> Allocated by task 4115:
>> save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
>> save_stack+0x43/0xd0 mm/kasan/kasan.c:502
>> set_track mm/kasan/kasan.c:514
>> kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:605
>> kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:544
>> slab_post_alloc_hook mm/slab.h:432
>> slab_alloc_node mm/slub.c:2708
>> slab_alloc mm/slub.c:2716
>> kmem_cache_alloc+0x1af/0x250 mm/slub.c:2721
>> sk_prot_alloc+0x65/0x2a0 net/core/sock.c:1334
>> sk_alloc+0x105/0x1010 net/core/sock.c:1396
>> inet6_create+0x44d/0x1150 net/ipv6/af_inet6.c:183
>> __sock_create+0x4f6/0x880 net/socket.c:1199
>> sock_create net/socket.c:1239
>> SYSC_socket net/socket.c:1269
>> SyS_socket+0xf9/0x230 net/socket.c:1249
>> entry_SYSCALL_64_fastpath+0x1f/0xc2 arch/x86/entry/entry_64.S:203
>>
>> Memory state around the buggy address:
>> ffff880062d9ff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>> ffff880062d9ff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>>ffff880062da0000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> ^
>> ffff880062da0080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> ffff880062da0100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> ==================================================================
>
> Sometimes this reproducer leads to another report:

Looks very similar to issue fixed in 8282f27449bf15548cb82c77b6e04ee0ab827bdc

Could you try :

diff --git a/net/ipv6/netfilter/nf_conntrack_reasm.c
b/net/ipv6/netfilter/nf_conntrack_reasm.c
index 9948b5ce52dad3a823edede517f17069bd7226dc..986d4ca38832b17703b09e50209ec133885c7276
100644
--- a/net/ipv6/netfilter/nf_conntrack_reasm.c
+++ b/net/ipv6/netfilter/nf_conntrack_reasm.c
@@ -589,6 +589,7 @@ int nf_ct_frag6_gather(struct net *net, struct
sk_buff *skb, u32 user)
hdr = ipv6_hdr(skb);
fhdr = (struct frag_hdr *)skb_transport_header(skb);

+ skb_orphan(skb);
fq = fq_find(net, fhdr->identification, user, &hdr->saddr, &hdr->daddr,
skb->dev ? skb->dev->ifindex : 0, ip6_frag_ecn(hdr));
if (fq == NULL) {
diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
index 6b78bab27755b2758f3c8ecd5b9c6d61615af4b6..fdec2a4cc559ab956c58d26535bdf010c0a8964a
100644
--- a/net/openvswitch/conntrack.c
+++ b/net/openvswitch/conntrack.c
@@ -367,7 +367,6 @@ static int handle_fragments(struct net *net,
struct sw_flow_key *key,
} else if (key->eth.type == htons(ETH_P_IPV6)) {
enum ip6_defrag_users user = IP6_DEFRAG_CONNTRACK_IN + zone;

- skb_orphan(skb);
memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
err = nf_ct_frag6_gather(net, skb, user);
if (err) {

Next message: Christoph Hellwig: "Re: [PATCH] libata-eh: Use switch() instead of sparse array for protocol strings"
Previous message: Andrey Konovalov: "net/atm: warning in alloc_tx/__might_sleep"
In reply to: Andrey Konovalov: "Re: net/ipv6: use-after-free in sock_wfree"
Next in thread: Andrey Konovalov: "Re: net/ipv6: use-after-free in sock_wfree"
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