bisecting fixing commit since c9fda4f22428e09728b611ec9100157199039bfe
building syzkaller on 1e35461e020a8b43c7b2d79ee64eb4068a9f0481
testing commit c9fda4f22428e09728b611ec9100157199039bfe with gcc (GCC) 8.1.0
kernel signature: e91582006063ed83072881046a9019db01e4d7b7498e539644dcc332791edf30
all runs: crashed: KASAN: use-after-free Read in ccid2_hc_tx_packet_recv
testing current HEAD 78d697fc93f98054e36a3ab76dca1a88802ba7be
testing commit 78d697fc93f98054e36a3ab76dca1a88802ba7be with gcc (GCC) 8.1.0
kernel signature: 0ce3c4d681ebc8ed301939c8d28e1dfe14cc82fd0406ca98e3df526a7febde72
all runs: crashed: KASAN: use-after-free Read in ccid2_hc_tx_packet_recv
revisions tested: 2, total time: 24m42.351467816s (build: 16m32.457092129s, test: 7m22.508226514s)
the crash still happens on HEAD
commit msg: Linux 4.14.172
crash: KASAN: use-after-free Read in ccid2_hc_tx_packet_recv
 should_failslab+0xba/0xf0 mm/failslab.c:32
 slab_pre_alloc_hook mm/slab.h:421 [inline]
 slab_alloc mm/slab.c:3376 [inline]
 kmem_cache_alloc_trace+0x2ea/0x7a0 mm/slab.c:3616
==================================================================
 kmalloc include/linux/slab.h:488 [inline]
 dccp_feat_entry_new+0x140/0x360 net/dccp/feat.c:467
 dccp_feat_push_confirm+0x26/0x280 net/dccp/feat.c:515
BUG: KASAN: use-after-free in ccid2_hc_tx_packet_recv+0x1edd/0x21d3 net/dccp/ccids/ccid2.c:599
Read of size 1 at addr ffff8880a81ed65d by task syz-executor.3/8787
 dccp_feat_handle_nn_established net/dccp/feat.c:1344 [inline]
 dccp_feat_parse_options+0xfe3/0x1a10 net/dccp/feat.c:1429

 dccp_parse_options+0x840/0xf20 net/dccp/options.c:128
 dccp_rcv_established+0x23/0x70 net/dccp/input.c:374
 dccp_v4_do_rcv+0xfa/0x160 net/dccp/ipv4.c:656
 sk_backlog_rcv include/net/sock.h:917 [inline]
 __release_sock+0x10b/0x340 net/core/sock.c:2264
 release_sock+0x4f/0x180 net/core/sock.c:2779
 dccp_sendmsg+0x4ab/0xc70 net/dccp/proto.c:813
 inet_sendmsg+0x108/0x440 net/ipv4/af_inet.c:762
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xb5/0xf0 net/socket.c:656
 ___sys_sendmsg+0x282/0x920 net/socket.c:2062
 __sys_sendmmsg+0x126/0x300 net/socket.c:2152
 SYSC_sendmmsg net/socket.c:2183 [inline]
 SyS_sendmmsg+0xd/0x20 net/socket.c:2178
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45a219
RSP: 002b:00007f560344ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f560344ac90 RCX: 000000000045a219
RDX: 04000000000001e6 RSI: 0000000020000c00 RDI: 0000000000000006
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f560344b6d4
R13: 00000000004c7f9d R14: 00000000004de3c8 R15: 0000000000000007
CPU: 1 PID: 8787 Comm: syz-executor.3 Not tainted 4.14.172-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xf7/0x13b lib/dump_stack.c:58
 print_address_description.cold.7+0x9/0x1c9 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report.cold.8+0x11a/0x2d3 mm/kasan/report.c:409
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:427
 ccid2_hc_tx_packet_recv+0x1edd/0x21d3 net/dccp/ccids/ccid2.c:599
 ccid_hc_tx_packet_recv net/dccp/ccid.h:192 [inline]
 dccp_deliver_input_to_ccids+0x19f/0x210 net/dccp/input.c:186
 dccp_rcv_established+0x49/0x70 net/dccp/input.c:378
 dccp_v4_do_rcv+0xfa/0x160 net/dccp/ipv4.c:656
 sk_backlog_rcv include/net/sock.h:917 [inline]
 __release_sock+0x10b/0x340 net/core/sock.c:2264
 release_sock+0x4f/0x180 net/core/sock.c:2779
 dccp_sendmsg+0x4ab/0xc70 net/dccp/proto.c:813
 inet_sendmsg+0x108/0x440 net/ipv4/af_inet.c:762
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xb5/0xf0 net/socket.c:656
 ___sys_sendmsg+0x282/0x920 net/socket.c:2062
 __sys_sendmmsg+0x126/0x300 net/socket.c:2152
 SYSC_sendmmsg net/socket.c:2183 [inline]
 SyS_sendmmsg+0xd/0x20 net/socket.c:2178
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45a219
RSP: 002b:00007fcdbe813c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007fcdbe813c90 RCX: 000000000045a219
RDX: 04000000000001e6 RSI: 0000000020000c00 RDI: 0000000000000006
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fcdbe8146d4
R13: 00000000004c7f9d R14: 00000000004de3c8 R15: 0000000000000007

CPU: 0 PID: 8792 Comm: syz-executor.1 Not tainted 4.14.172-syzkaller #0
Allocated by task 8787:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
Call Trace:
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:551
 __do_kmalloc_node mm/slab.c:3682 [inline]
 __kmalloc_node_track_caller+0x50/0x70 mm/slab.c:3696
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xf7/0x13b lib/dump_stack.c:58
 __kmalloc_reserve.isra.36+0x2c/0xc0 net/core/skbuff.c:137
 fail_dump lib/fault-inject.c:51 [inline]
 should_fail.cold.3+0x105/0x14b lib/fault-inject.c:149
 __alloc_skb+0xc1/0x500 net/core/skbuff.c:205
 should_failslab+0xba/0xf0 mm/failslab.c:32
 alloc_skb include/linux/skbuff.h:980 [inline]
 dccp_send_ack+0xb3/0x340 net/dccp/output.c:580
 slab_pre_alloc_hook mm/slab.h:421 [inline]
 slab_alloc mm/slab.c:3376 [inline]
 kmem_cache_alloc_trace+0x2ea/0x7a0 mm/slab.c:3616
 ccid2_hc_rx_packet_recv+0xf9/0x170 net/dccp/ccids/ccid2.c:778
 ccid_hc_rx_packet_recv net/dccp/ccid.h:185 [inline]
 dccp_deliver_input_to_ccids+0xc5/0x210 net/dccp/input.c:180
 kmalloc include/linux/slab.h:488 [inline]
 dccp_feat_entry_new+0x140/0x360 net/dccp/feat.c:467
 dccp_rcv_established+0x49/0x70 net/dccp/input.c:378
 dccp_feat_push_confirm+0x26/0x280 net/dccp/feat.c:515
 dccp_v4_do_rcv+0xfa/0x160 net/dccp/ipv4.c:656
 sk_backlog_rcv include/net/sock.h:917 [inline]
 __sk_receive_skb+0x1d5/0x820 net/core/sock.c:511
 dccp_feat_handle_nn_established net/dccp/feat.c:1344 [inline]
 dccp_feat_parse_options+0xfe3/0x1a10 net/dccp/feat.c:1429
 dccp_v4_rcv+0xc26/0x1bbf net/dccp/ipv4.c:877
 ip_local_deliver_finish+0x230/0x9a0 net/ipv4/ip_input.c:216
 NF_HOOK include/linux/netfilter.h:250 [inline]
 ip_local_deliver+0x1a0/0x410 net/ipv4/ip_input.c:257
 dst_input include/net/dst.h:468 [inline]
 ip_rcv_finish+0x70d/0x1950 net/ipv4/ip_input.c:396
 NF_HOOK include/linux/netfilter.h:250 [inline]
 ip_rcv+0xb43/0x133d net/ipv4/ip_input.c:493
 __netif_receive_skb_core+0x1d1a/0x2e40 net/core/dev.c:4477
 __netif_receive_skb+0x1f/0x1b0 net/core/dev.c:4515
 process_backlog+0x1fc/0x710 net/core/dev.c:5197
 dccp_parse_options+0x840/0xf20 net/dccp/options.c:128
 napi_poll net/core/dev.c:5598 [inline]
 net_rx_action+0x458/0xed0 net/core/dev.c:5664
 dccp_rcv_established+0x23/0x70 net/dccp/input.c:374
 __do_softirq+0x246/0x9b0 kernel/softirq.c:288
 dccp_v4_do_rcv+0xfa/0x160 net/dccp/ipv4.c:656

 sk_backlog_rcv include/net/sock.h:917 [inline]
 __release_sock+0x10b/0x340 net/core/sock.c:2264
Freed by task 8787:
 release_sock+0x4f/0x180 net/core/sock.c:2779
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 dccp_sendmsg+0x4ab/0xc70 net/dccp/proto.c:813
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kfree+0xcc/0x270 mm/slab.c:3815
 skb_free_head+0x74/0x90 net/core/skbuff.c:554
 skb_release_data+0x43b/0x790 net/core/skbuff.c:574
 skb_release_all+0x3d/0x50 net/core/skbuff.c:631
 __kfree_skb net/core/skbuff.c:645 [inline]
 kfree_skb+0x8a/0x2b0 net/core/skbuff.c:663
 inet_sendmsg+0x108/0x440 net/ipv4/af_inet.c:762
 dccp_v4_do_rcv+0x111/0x160 net/dccp/ipv4.c:691
 sk_backlog_rcv include/net/sock.h:917 [inline]
 __release_sock+0x10b/0x340 net/core/sock.c:2264
 release_sock+0x4f/0x180 net/core/sock.c:2779
 dccp_sendmsg+0x4ab/0xc70 net/dccp/proto.c:813
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xb5/0xf0 net/socket.c:656
 inet_sendmsg+0x108/0x440 net/ipv4/af_inet.c:762
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xb5/0xf0 net/socket.c:656
 ___sys_sendmsg+0x282/0x920 net/socket.c:2062
 ___sys_sendmsg+0x282/0x920 net/socket.c:2062
 __sys_sendmmsg+0x126/0x300 net/socket.c:2152
 SYSC_sendmmsg net/socket.c:2183 [inline]
 SyS_sendmmsg+0xd/0x20 net/socket.c:2178
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8880a81ed1c0
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1181 bytes inside of
 2048-byte region [ffff8880a81ed1c0, ffff8880a81ed9c0)
The buggy address belongs to the page:
page:ffffea0002a07b00 count:1 mapcount:0 mapping:ffff8880a81ec0c0 index:0x0
 compound_mapcount: 0
 __sys_sendmmsg+0x126/0x300 net/socket.c:2152
flags: 0x1fffc0000008100(slab|head)
raw: 01fffc0000008100 ffff8880a81ec0c0 0000000000000000 0000000100000003
raw: ffffea00028667a0 ffffea0002844a20 ffff8880aa800c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a81ed500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a81ed580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 SYSC_sendmmsg net/socket.c:2183 [inline]
 SyS_sendmmsg+0xd/0x20 net/socket.c:2178
>ffff8880a81ed600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
                                                    ^
 ffff8880a81ed680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a81ed700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================