bisecting fixing commit since 672481c2deffb371d8a7dfdc009e44c09864a869 building syzkaller on bc5869180f69e2ad6c6b823e129e08a8e523d800 testing commit 672481c2deffb371d8a7dfdc009e44c09864a869 with gcc (GCC) 8.1.0 kernel signature: 81c2eaaeb9347737b3757593b1c503dd9bc1ebf5899a927d5359f24bb7813b67 all runs: crashed: KASAN: use-after-free Read in n_tty_receive_buf_common testing current HEAD 357668399cf70ccdc0ee8967bff3448d0f4f9ae1 testing commit 357668399cf70ccdc0ee8967bff3448d0f4f9ae1 with gcc (GCC) 8.1.0 kernel signature: 3f6bc807e985caa80a23f3d029e3e55a12c24f15b63a4ab12ca8750c74f1277c all runs: crashed: KASAN: use-after-free Read in n_tty_receive_buf_common revisions tested: 2, total time: 25m35.202366623s (build: 17m49.878533764s, test: 6m43.601452182s) the crash still happens on HEAD commit msg: Linux 4.19.103 crash: KASAN: use-after-free Read in n_tty_receive_buf_common IPv6: ADDRCONF(NETDEV_CHANGE): vxcan1: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vxcan0: link becomes ready ================================================================== BUG: KASAN: use-after-free in put_tty_queue drivers/tty/n_tty.c:317 [inline] BUG: KASAN: use-after-free in n_tty_receive_char_inline drivers/tty/n_tty.c:1424 [inline] BUG: KASAN: use-after-free in n_tty_receive_buf_standard drivers/tty/n_tty.c:1581 [inline] BUG: KASAN: use-after-free in __receive_buf drivers/tty/n_tty.c:1644 [inline] BUG: KASAN: use-after-free in n_tty_receive_buf_common+0x1ee5/0x2b80 drivers/tty/n_tty.c:1740 Read of size 1 at addr ffff888083351428 by task syz-executor.5/8253 CPU: 1 PID: 8253 Comm: syz-executor.5 Not tainted 4.19.103-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+0x123/0x177 lib/dump_stack.c:118 print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430 put_tty_queue drivers/tty/n_tty.c:317 [inline] n_tty_receive_char_inline drivers/tty/n_tty.c:1424 [inline] n_tty_receive_buf_standard drivers/tty/n_tty.c:1581 [inline] __receive_buf drivers/tty/n_tty.c:1644 [inline] n_tty_receive_buf_common+0x1ee5/0x2b80 drivers/tty/n_tty.c:1740 n_tty_receive_buf2+0xf/0x20 drivers/tty/n_tty.c:1775 tty_ldisc_receive_buf+0x86/0x1b0 drivers/tty/tty_buffer.c:456 paste_selection+0x26c/0x3c0 drivers/tty/vt/selection.c:359 tioclinux+0x10b/0x3a0 drivers/tty/vt/vt.c:3019 vt_ioctl+0x1882/0x2130 drivers/tty/vt/vt_ioctl.c:364 tty_ioctl+0x452/0x1290 drivers/tty/tty_io.c:2669 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45a919 Code: ad 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f9e7d6e6c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a919 RDX: 0000000020000040 RSI: 000000000000541c RDI: 0000000000000003 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f9e7d6e76d4 R13: 00000000004c5c45 R14: 00000000004dc018 R15: 00000000ffffffff Allocated by task 8262: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553 __do_kmalloc mm/slab.c:3727 [inline] __kmalloc+0x15b/0x770 mm/slab.c:3736 kmalloc_array include/linux/slab.h:637 [inline] set_selection+0x650/0x1030 drivers/tty/vt/selection.c:293 tioclinux+0xf6/0x3a0 drivers/tty/vt/vt.c:3015 vt_ioctl+0x1882/0x2130 drivers/tty/vt/vt_ioctl.c:364 tty_ioctl+0x452/0x1290 drivers/tty/tty_io.c:2669 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe Freed by task 8266: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 __cache_free mm/slab.c:3503 [inline] kfree+0xcf/0x220 mm/slab.c:3822 set_selection+0x675/0x1030 drivers/tty/vt/selection.c:300 tioclinux+0xf6/0x3a0 drivers/tty/vt/vt.c:3015 vt_ioctl+0x1882/0x2130 drivers/tty/vt/vt_ioctl.c:364 tty_ioctl+0x452/0x1290 drivers/tty/tty_io.c:2669 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 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 ffff888083351400 which belongs to the cache kmalloc-16384 of size 16384 The buggy address is located 40 bytes inside of 16384-byte region [ffff888083351400, ffff888083355400) The buggy address belongs to the page: page:ffffea00020cd400 count:1 mapcount:0 mapping:ffff88812c295200 index:0x0 compound_mapcount: 0 flags: 0xfffe0000008100(slab|head) raw: 00fffe0000008100 ffffea000260ee08 ffffea00020cd608 ffff88812c295200 raw: 0000000000000000 ffff888083351400 0000000100000001 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888083351300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888083351380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff888083351400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888083351480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888083351500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================