bisecting fixing commit since c9fda4f22428e09728b611ec9100157199039bfe building syzkaller on 1e35461e020a8b43c7b2d79ee64eb4068a9f0481 testing commit c9fda4f22428e09728b611ec9100157199039bfe with gcc (GCC) 8.1.0 kernel signature: 2803a2e12402db6a0e56852415c4c7b732cca7ae all runs: crashed: KASAN: use-after-free Read in ccid2_hc_tx_packet_recv testing current HEAD 84f5ad468100f86d70096799e4ee716a17c2962f testing commit 84f5ad468100f86d70096799e4ee716a17c2962f with gcc (GCC) 8.1.0 kernel signature: aa938f2d942ca887a96389c4723567af9ff05ea6 all runs: crashed: KASAN: use-after-free Read in ccid2_hc_tx_packet_recv revisions tested: 2, total time: 24m33.529970133s (build: 16m22.77191371s, test: 7m17.965088108s) the crash still happens on HEAD commit msg: Linux 4.14.162 crash: KASAN: use-after-free Read in ccid2_hc_tx_packet_recv RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f333f6fc6d4 R13: 00000000004c7f9d R14: 00000000004de3c8 R15: 0000000000000007 dccp_parse_options: DCCP(ffff88808f544b40): Option 32 (len=7) error=9 ================================================================== 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 ffff888094a5b99d by task syz-executor.3/6815 CPU: 1 PID: 6815 Comm: syz-executor.3 Not tainted 4.14.162-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:00007f333f6fbc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 RAX: ffffffffffffffda RBX: 00007f333f6fbc90 RCX: 000000000045a219 RDX: 04000000000001e6 RSI: 0000000020000c00 RDI: 0000000000000006 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f333f6fc6d4 R13: 00000000004c7f9d R14: 00000000004de3c8 R15: 0000000000000007 Allocated by task 6815: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x43/0xd0 mm/kasan/kasan.c:447 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 __kmalloc_reserve.isra.36+0x2c/0xc0 net/core/skbuff.c:137 __alloc_skb+0xc1/0x500 net/core/skbuff.c:205 alloc_skb include/linux/skbuff.h:980 [inline] dccp_send_ack+0xb3/0x340 net/dccp/output.c:580 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 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] __sk_receive_skb+0x1d5/0x820 net/core/sock.c:511 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 napi_poll net/core/dev.c:5598 [inline] net_rx_action+0x458/0xed0 net/core/dev.c:5664 __do_softirq+0x246/0x9b0 kernel/softirq.c:288 Freed by task 6815: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 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 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 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 The buggy address belongs to the object at ffff888094a5b500 which belongs to the cache kmalloc-2048 of size 2048 The buggy address is located 1181 bytes inside of 2048-byte region [ffff888094a5b500, ffff888094a5bd00) The buggy address belongs to the page: page:ffffea0002529680 count:1 mapcount:0 mapping:ffff888094a5a400 index:0x0 compound_mapcount: 0 flags: 0x1fffc0000008100(slab|head) raw: 01fffc0000008100 ffff888094a5a400 0000000000000000 0000000100000003 raw: ffffea0002533ba0 ffffea00025297a0 ffff8880aa800c40 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888094a5b880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888094a5b900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888094a5b980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888094a5ba00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888094a5ba80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================