bisecting fixing commit since 2c8a3fceddf0dd87f278e7a5e01350f86f844b1c building syzkaller on 624dad51316f9973e1349b6c71e789737d1e00d9 testing commit 2c8a3fceddf0dd87f278e7a5e01350f86f844b1c with gcc (GCC) 8.4.1 20210217 kernel signature: 8ee020f3ed25dc34b442cd269c6cad8e98a6dea28a72e9c30cfe487699c9b3af run #0: crashed: KASAN: use-after-free Read in chrdev_open run #1: crashed: KASAN: use-after-free Read in chrdev_open run #2: crashed: KASAN: use-after-free Read in chrdev_open run #3: crashed: KASAN: use-after-free Read in chrdev_open run #4: crashed: KASAN: use-after-free Read in chrdev_open run #5: crashed: KASAN: use-after-free Read in chrdev_open run #6: crashed: KASAN: use-after-free Read in chrdev_open run #7: crashed: KASAN: use-after-free Read in chrdev_open run #8: crashed: KASAN: use-after-free Read in chrdev_open run #9: crashed: KASAN: use-after-free Read in chrdev_open run #10: crashed: KASAN: use-after-free Read in chrdev_open run #11: crashed: KASAN: use-after-free Read in chrdev_open run #12: crashed: KASAN: use-after-free Read in chrdev_open run #13: crashed: KASAN: use-after-free Read in chrdev_open run #14: crashed: KASAN: use-after-free Read in chrdev_open run #15: crashed: KASAN: use-after-free Read in cd_forget run #16: crashed: KASAN: use-after-free Read in chrdev_open run #17: crashed: KASAN: use-after-free Read in chrdev_open run #18: crashed: KASAN: use-after-free Read in chrdev_open run #19: crashed: KASAN: use-after-free Read in chrdev_open testing current HEAD bd634aa6416382439890b78f7be0023020a86207 testing commit bd634aa6416382439890b78f7be0023020a86207 with gcc (GCC) 8.4.1 20210217 kernel signature: e356c0c85606bb4b10e15d7589a0efdaa2e8905a62e15b8aed73aeaf0c69ede2 all runs: crashed: KASAN: use-after-free Read in chrdev_open revisions tested: 2, total time: 23m58.237928137s (build: 17m10.408377367s, test: 6m26.452610964s) the crash still happens on HEAD commit msg: Linux 4.14.228 crash: KASAN: use-after-free Read in chrdev_open 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 __list_add_valid+0x7d/0xb0 lib/list_debug.c:23 Read of size 8 at addr ffff8880b35cf148 by task syz-executor.3/9998 CPU: 0 PID: 9998 Comm: syz-executor.3 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 __list_add_valid+0x7d/0xb0 lib/list_debug.c:23 __list_add include/linux/list.h:60 [inline] list_add include/linux/list.h:79 [inline] chrdev_open+0x374/0x5b0 fs/char_dev.c:405 do_dentry_open+0x3e4/0xde0 fs/open.c:777 vfs_open+0xfc/0x240 fs/open.c:888 do_last fs/namei.c:3428 [inline] path_openat+0xb6f/0x2760 fs/namei.c:3569 do_filp_open+0x16b/0x220 fs/namei.c:3603 do_sys_open+0x1d0/0x350 fs/open.c:1081 SYSC_open fs/open.c:1099 [inline] SyS_open fs/open.c:1094 [inline] SYSC_creat fs/open.c:1139 [inline] SyS_creat+0x19/0x20 fs/open.c:1137 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x465b09 RSP: 002b:00007fe929221188 EFLAGS: 00000246 ORIG_RAX: 0000000000000055 RAX: ffffffffffffffda RBX: 000000000056c158 RCX: 0000000000465b09 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200001c0 RBP: 00000000004b069f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c158 R13: 00007ffd046a1dbf R14: 00007fe929221300 R15: 0000000000022000 Allocated by task 9920: 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 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489 kmem_cache_alloc+0x12e/0x3e0 mm/slab.c:3552 fuse_alloc_inode+0x1c/0x3b0 fs/fuse/inode.c:87 alloc_inode+0x56/0x150 fs/inode.c:210 iget5_locked+0x13f/0x3f0 fs/inode.c:1050 fuse_iget+0x18a/0x6f0 fs/fuse/inode.c:307 fuse_lookup_name+0x337/0x570 fs/fuse/dir.c:341 fuse_lookup+0xe4/0x380 fs/fuse/dir.c:368 fuse_atomic_open+0x193/0x320 fs/fuse/dir.c:508 atomic_open fs/namei.c:3075 [inline] lookup_open+0xdb0/0x1c10 fs/namei.c:3211 do_last fs/namei.c:3334 [inline] path_openat+0xe81/0x2760 fs/namei.c:3569 do_filp_open+0x16b/0x220 fs/namei.c:3603 do_sys_open+0x1d0/0x350 fs/open.c:1081 SYSC_open fs/open.c:1099 [inline] SyS_open fs/open.c:1094 [inline] SYSC_creat fs/open.c:1139 [inline] SyS_creat+0x19/0x20 fs/open.c:1137 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb Freed by task 17: 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] kmem_cache_free+0x80/0x2d0 mm/slab.c:3758 fuse_i_callback+0x17/0x20 fs/fuse/inode.c:116 __rcu_reclaim kernel/rcu/rcu.h:195 [inline] rcu_do_batch kernel/rcu/tree.c:2699 [inline] invoke_rcu_callbacks kernel/rcu/tree.c:2962 [inline] __rcu_process_callbacks kernel/rcu/tree.c:2929 [inline] rcu_process_callbacks+0x7a5/0x11e0 kernel/rcu/tree.c:2946 __do_softirq+0x247/0x9a2 kernel/softirq.c:288 The buggy address belongs to the object at ffff8880b35cedc0 which belongs to the cache fuse_inode of size 1272 The buggy address is located 904 bytes inside of 1272-byte region [ffff8880b35cedc0, ffff8880b35cf2b8) The buggy address belongs to the page: page:ffffea0002cd7380 count:1 mapcount:0 mapping:ffff8880b35ce2c0 index:0xffff8880b35cfffb compound_mapcount: 0 flags: 0xfff00000008100(slab|head) raw: 00fff00000008100 ffff8880b35ce2c0 ffff8880b35cfffb 0000000100000005 raw: ffffea00025a4f20 ffffea00025635a0 ffff88823927e0c0 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880b35cf000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880b35cf080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8880b35cf100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8880b35cf180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880b35cf200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================