bisecting fixing commit since dce0f88600e49746b4bda873965b671a23ff4313 building syzkaller on 115e19300f73966554f176e2440fe79572a37c99 testing commit dce0f88600e49746b4bda873965b671a23ff4313 with gcc (GCC) 8.1.0 kernel signature: a5d9bca408efac8ee0ec16e0d35c4f11d7e27c3f7d749d80ab57f13c55dd31d8 run #0: crashed: KASAN: slab-out-of-bounds Read in get_block run #1: crashed: KASAN: use-after-free Read in get_block run #2: crashed: KASAN: use-after-free Read in get_block run #3: crashed: KASAN: slab-out-of-bounds Read in get_block run #4: crashed: KASAN: slab-out-of-bounds Read in get_block run #5: crashed: KASAN: use-after-free Read in get_block run #6: crashed: KASAN: use-after-free Read in get_block run #7: crashed: KASAN: use-after-free Read in get_block run #8: crashed: KASAN: slab-out-of-bounds Read in get_block run #9: crashed: KASAN: slab-out-of-bounds Read in get_block testing current HEAD c14d30dc9987047b439b03d6e6db7d54d9f7f180 testing commit c14d30dc9987047b439b03d6e6db7d54d9f7f180 with gcc (GCC) 8.1.0 kernel signature: d360b5e0a159ab6e0ee13899731c0ec4a39b425c20e176f569ea743bf0c644ac run #0: crashed: KASAN: use-after-free Read in get_block run #1: crashed: KASAN: slab-out-of-bounds Read in get_block run #2: crashed: KASAN: slab-out-of-bounds Read in V1_minix_truncate run #3: crashed: KASAN: slab-out-of-bounds Read in V1_minix_truncate run #4: crashed: KASAN: slab-out-of-bounds Read in get_block run #5: crashed: KASAN: slab-out-of-bounds Read in get_block run #6: crashed: KASAN: use-after-free Read in get_block run #7: crashed: KASAN: slab-out-of-bounds Read in get_block run #8: crashed: KASAN: use-after-free Read in get_block run #9: crashed: KASAN: use-after-free Read in get_block revisions tested: 2, total time: 25m52.141760612s (build: 18m28.711439873s, test: 6m13.70396342s) the crash still happens on HEAD commit msg: Linux 4.19.139 crash: KASAN: use-after-free Read in get_block minix_free_block (loop2:147): bit already cleared Process accounting resumed minix_free_block (loop3:147): bit already cleared Process accounting resumed ================================================================== BUG: KASAN: use-after-free in add_chain fs/minix/itree_common.c:14 [inline] BUG: KASAN: use-after-free in get_branch fs/minix/itree_common.c:52 [inline] BUG: KASAN: use-after-free in get_block+0xe25/0x1100 fs/minix/itree_common.c:160 Read of size 2 at addr ffff8880926a218a by task syz-executor.1/7901 CPU: 1 PID: 7901 Comm: syz-executor.1 Not tainted 4.19.139-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x17c/0x22a lib/dump_stack.c:118 print_address_description.cold.6+0x9/0x211 mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report.cold.7+0x242/0x307 mm/kasan/report.c:412 __asan_report_load2_noabort+0x14/0x20 mm/kasan/report.c:431 add_chain fs/minix/itree_common.c:14 [inline] get_branch fs/minix/itree_common.c:52 [inline] get_block+0xe25/0x1100 fs/minix/itree_common.c:160 V1_minix_get_block+0x9/0x10 fs/minix/itree_v1.c:56 minix_get_block+0xa7/0x110 fs/minix/inode.c:379 __block_write_begin_int+0x392/0x1aa0 fs/buffer.c:1978 __block_write_begin fs/buffer.c:2028 [inline] block_write_begin+0x48/0x260 fs/buffer.c:2087 minix_write_begin+0x2f/0xc0 fs/minix/inode.c:415 generic_perform_write+0x22f/0x480 mm/filemap.c:3162 __generic_file_write_iter+0x201/0x580 mm/filemap.c:3287 generic_file_write_iter+0x302/0x655 mm/filemap.c:3315 call_write_iter include/linux/fs.h:1821 [inline] new_sync_write fs/read_write.c:474 [inline] __vfs_write+0x443/0x890 fs/read_write.c:487 __kernel_write+0xe4/0x350 fs/read_write.c:506 do_acct_process+0xa6c/0xea0 kernel/acct.c:520 slow_acct_process kernel/acct.c:579 [inline] acct_process+0x39f/0x49e kernel/acct.c:605 do_exit+0x1a9c/0x2db0 kernel/exit.c:877 do_group_exit+0xf8/0x2c0 kernel/exit.c:990 get_signal+0x308/0x1970 kernel/signal.c:2588 do_signal+0x87/0x1860 arch/x86/kernel/signal.c:821 exit_to_usermode_loop+0x159/0x1e0 arch/x86/entry/common.c:163 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline] syscall_return_slowpath arch/x86/entry/common.c:271 [inline] do_syscall_64+0x413/0x4e0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45cba9 Code: 8d b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 5b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f49355f0c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a3 RAX: 0000000000000000 RBX: 00000000004da400 RCX: 000000000045cba9 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000480 RBP: 000000000078bfa0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 000000000000001c R14: 00000000004c2f71 R15: 00007f49355f16d4 Allocated by task 6576: save_stack mm/kasan/kasan.c:448 [inline] set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc.part.1+0x62/0xf0 mm/kasan/kasan.c:553 kasan_kmalloc+0xaf/0xc0 mm/kasan/kasan.c:538 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490 kmem_cache_alloc_node+0x14f/0x3e0 mm/slab.c:3649 __alloc_skb+0xa7/0x580 net/core/skbuff.c:193 alloc_skb include/linux/skbuff.h:995 [inline] nlmsg_new include/net/netlink.h:511 [inline] netlink_ack+0x20f/0x980 net/netlink/af_netlink.c:2389 netlink_rcv_skb+0x2a8/0x3d0 net/netlink/af_netlink.c:2461 rtnetlink_rcv+0x10/0x20 net/core/rtnetlink.c:4796 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x443/0x660 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x666/0xc50 net/netlink/af_netlink.c:1909 sock_sendmsg_nosec net/socket.c:622 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:632 __sys_sendto+0x1f2/0x2e0 net/socket.c:1787 __do_sys_sendto net/socket.c:1799 [inline] __se_sys_sendto net/socket.c:1795 [inline] __x64_sys_sendto+0xdc/0x1a0 net/socket.c:1795 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe Freed by task 6576: save_stack mm/kasan/kasan.c:448 [inline] set_track mm/kasan/kasan.c:460 [inline] __kasan_slab_free+0x13c/0x220 mm/kasan/kasan.c:521 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 __cache_free mm/slab.c:3503 [inline] kmem_cache_free+0x83/0x290 mm/slab.c:3765 kfree_skbmem+0x89/0xf0 net/core/skbuff.c:586 __kfree_skb net/core/skbuff.c:646 [inline] consume_skb+0x9b/0x270 net/core/skbuff.c:705 skb_free_datagram+0x12/0xc0 net/core/datagram.c:329 netlink_recvmsg+0x5e6/0xe70 net/netlink/af_netlink.c:1988 sock_recvmsg_nosec net/socket.c:795 [inline] sock_recvmsg+0xb7/0xf0 net/socket.c:802 __sys_recvfrom+0x327/0x3f0 net/socket.c:1844 __do_sys_recvfrom net/socket.c:1862 [inline] __se_sys_recvfrom net/socket.c:1858 [inline] __x64_sys_recvfrom+0xdc/0x1a0 net/socket.c:1858 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe The buggy address belongs to the object at ffff8880926a2180 which belongs to the cache skbuff_head_cache of size 232 The buggy address is located 10 bytes inside of 232-byte region [ffff8880926a2180, ffff8880926a2268) The buggy address belongs to the page: page:ffffea000249a880 count:1 mapcount:0 mapping:ffff88821babab40 index:0x0 flags: 0xfffe0000000100(slab) raw: 00fffe0000000100 ffffea00024d4348 ffffea0002480048 ffff88821babab40 raw: 0000000000000000 ffff8880926a2040 000000010000000c 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880926a2080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880926a2100: fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc >ffff8880926a2180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8880926a2200: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc ffff8880926a2280: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb 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