bisecting fixing commit since 29c52025152bab4c557d8174da58f1a4c8e70438 building syzkaller on a659b3f1dc889d5ab5ead017b877765b3d042379 testing commit 29c52025152bab4c557d8174da58f1a4c8e70438 with gcc (GCC) 8.4.1 20210217 kernel signature: 2c944fae21b8abf47753bf6c11734c710d934a0d286137e0b770aed0a2e0b857 run #0: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #1: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #2: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #3: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #4: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #5: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #6: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #7: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #8: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #9: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #10: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #11: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #12: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #13: OK run #14: OK run #15: OK run #16: OK run #17: OK run #18: OK run #19: OK testing current HEAD bd634aa6416382439890b78f7be0023020a86207 testing commit bd634aa6416382439890b78f7be0023020a86207 with gcc (GCC) 8.4.1 20210217 kernel signature: 88540f61c88d714c519401c3bd3dc4d800f1322623f83fb75e93d6175edba4b3 run #0: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #1: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #2: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #3: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #4: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #5: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #6: OK run #7: OK run #8: crashed: KASAN: use-after-free Read in ip_check_mc_rcu run #9: OK revisions tested: 2, total time: 38m41.569644597s (build: 15m11.236458375s, test: 23m5.615390447s) the crash still happens on HEAD commit msg: Linux 4.14.228 crash: KASAN: use-after-free Read in ip_check_mc_rcu IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_batadv: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_1: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready ================================================================== BUG: KASAN: use-after-free in ip_check_mc_rcu+0x4d4/0x530 net/ipv4/igmp.c:2697 Read of size 8 at addr ffff8880b5324b80 by task syz-executor029/29803 CPU: 0 PID: 29803 Comm: syz-executor029 Not tainted 4.14.228-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+0x14b/0x1e7 lib/dump_stack.c:58 print_address_description.cold.6+0x9/0x1ca mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report mm/kasan/report.c:409 [inline] kasan_report.cold.7+0x11a/0x2d3 mm/kasan/report.c:393 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430 ip_check_mc_rcu+0x4d4/0x530 net/ipv4/igmp.c:2697 __mkroute_output net/ipv4/route.c:2234 [inline] ip_route_output_key_hash_rcu+0x1b1c/0x2570 net/ipv4/route.c:2516 ip_route_output_key_hash+0x187/0x280 net/ipv4/route.c:2344 __ip_route_output_key include/net/route.h:126 [inline] ip_route_output_flow+0x1f/0x140 net/ipv4/route.c:2601 udp_sendmsg+0x109c/0x1dd0 net/ipv4/udp.c:1025 inet_sendmsg+0x108/0x440 net/ipv4/af_inet.c:762 sock_sendmsg_nosec net/socket.c:646 [inline] sock_sendmsg+0xac/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+0x46/0xbb RIP: 0033:0x448fc9 RSP: 002b:00007f25ae8e4318 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 RAX: ffffffffffffffda RBX: 00000000004ce4e8 RCX: 0000000000448fc9 RDX: 000000000800001d RSI: 0000000020007fc0 RDI: 0000000000000003 RBP: 00000000004ce4e0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000049d474 R13: 00007ffc6e8afb1f R14: 00007f25ae8e4400 R15: 0000000000022000 Allocated by task 29803: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack mm/kasan/kasan.c:447 [inline] set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc.part.1+0x62/0xf0 mm/kasan/kasan.c:551 kasan_kmalloc+0xaf/0xc0 mm/kasan/kasan.c:536 kmem_cache_alloc_trace+0x152/0x3f0 mm/slab.c:3618 kmalloc include/linux/slab.h:488 [inline] kzalloc include/linux/slab.h:661 [inline] ip_mc_add1_src net/ipv4/igmp.c:1960 [inline] ip_mc_add_src+0x92f/0xe30 net/ipv4/igmp.c:2084 ip_mc_source+0x871/0xf90 net/ipv4/igmp.c:2390 do_ip_setsockopt.isra.4+0x1853/0x27c0 net/ipv4/ip_sockglue.c:995 ip_setsockopt+0x27/0x70 net/ipv4/ip_sockglue.c:1248 tcp_setsockopt net/ipv4/tcp.c:2828 [inline] tcp_setsockopt+0x6a/0xd0 net/ipv4/tcp.c:2822 sock_common_setsockopt+0x73/0xf0 net/core/sock.c:2994 SYSC_setsockopt net/socket.c:1865 [inline] SyS_setsockopt+0x130/0x1f0 net/socket.c:1844 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb Freed by task 29802: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack mm/kasan/kasan.c:447 [inline] set_track mm/kasan/kasan.c:459 [inline] kasan_slab_free+0xab/0x190 mm/kasan/kasan.c:524 __cache_free mm/slab.c:3496 [inline] kfree+0xcc/0x270 mm/slab.c:3815 ip_mc_del1_src+0x537/0x750 net/ipv4/igmp.c:1873 ip_mc_del_src+0x3d3/0x8e0 net/ipv4/igmp.c:1914 ip_mc_leave_src+0xd7/0x1f0 net/ipv4/igmp.c:2205 ip_mc_drop_socket+0xff/0x1f0 net/ipv4/igmp.c:2659 inet_release+0x47/0x1c0 net/ipv4/af_inet.c:411 __sock_release+0xc2/0x2a0 net/socket.c:602 sock_close+0x10/0x20 net/socket.c:1139 __fput+0x232/0x740 fs/file_table.c:210 ____fput+0x9/0x10 fs/file_table.c:244 task_work_run+0xe5/0x170 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:191 [inline] exit_to_usermode_loop+0x14a/0x190 arch/x86/entry/common.c:164 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline] syscall_return_slowpath arch/x86/entry/common.c:270 [inline] do_syscall_64+0x416/0x5b0 arch/x86/entry/common.c:297 entry_SYSCALL_64_after_hwframe+0x46/0xbb The buggy address belongs to the object at ffff8880b5324b80 which belongs to the cache kmalloc-64 of size 64 The buggy address is located 0 bytes inside of 64-byte region [ffff8880b5324b80, ffff8880b5324bc0) The buggy address belongs to the page: page:ffffea0002d4c900 count:1 mapcount:0 mapping:ffff8880b5324000 index:0xffff8880b5324800 flags: 0xfff00000000100(slab) raw: 00fff00000000100 ffff8880b5324000 ffff8880b5324800 0000000100000014 raw: ffffea0002492420 ffffea0002cd9660 ffff88813fe60340 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880b5324a80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ffff8880b5324b00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc >ffff8880b5324b80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ^ ffff8880b5324c00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc ffff8880b5324c80: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc ==================================================================