bisecting fixing commit since cbfa1702aaf69b2311ea1b35e04f113c48368c67 building syzkaller on 1880b4a9f394370a7d1fcb5c1cfca0fa1127b463 testing commit cbfa1702aaf69b2311ea1b35e04f113c48368c67 with gcc (GCC) 8.1.0 kernel signature: e96c5b4a7e18ea9a80bf0d282a3183132d2e70ad135e0baa6b6ea9add6887ec6 run #0: crashed: KASAN: slab-out-of-bounds Read in soft_cursor run #1: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #2: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #3: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #4: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #5: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #6: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #7: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #8: crashed: KASAN: use-after-free Read in bit_putcs run #9: crashed: KASAN: slab-out-of-bounds Read in bit_putcs testing current HEAD 3f2ecb86cb909da0b9157fd2952ad79924cbe5ae testing commit 3f2ecb86cb909da0b9157fd2952ad79924cbe5ae with gcc (GCC) 8.1.0 kernel signature: 380770fcec248e434f3280392026a451cac51893fd011b36058144f51497b638 all runs: crashed: KASAN: slab-out-of-bounds Read in bit_putcs revisions tested: 2, total time: 24m4.472722063s (build: 17m41.19270903s, test: 5m45.932796344s) the crash still happens on HEAD commit msg: Linux 4.14.212 crash: KASAN: slab-out-of-bounds Read in bit_putcs IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_batadv: link becomes ready IPv6: ADDRCONF(NETDEV_UP): veth1_to_batadv: link is not ready batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0 ================================================================== BUG: KASAN: slab-out-of-bounds in __fb_pad_aligned_buffer include/linux/fb.h:663 [inline] BUG: KASAN: slab-out-of-bounds in bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline] BUG: KASAN: slab-out-of-bounds in bit_putcs+0x931/0xc80 drivers/video/fbdev/core/bitblit.c:185 Read of size 1 at addr ffff8881d4d636be by task syz-executor.5/7206 CPU: 0 PID: 7206 Comm: syz-executor.5 Not tainted 4.14.212-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/0x1f1 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.cold.7+0x11a/0x2d4 mm/kasan/report.c:409 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:427 __fb_pad_aligned_buffer include/linux/fb.h:663 [inline] bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline] bit_putcs+0x931/0xc80 drivers/video/fbdev/core/bitblit.c:185 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! fbcon_putcs+0x302/0x5f0 drivers/video/fbdev/core/fbcon.c:1247 batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0 con_flush drivers/tty/vt/vt.c:2206 [inline] do_con_write.part.13+0x9a5/0x19c0 drivers/tty/vt/vt.c:2453 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0 batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems! do_con_write drivers/tty/vt/vt.c:2225 [inline] con_write+0x1f/0x80 drivers/tty/vt/vt.c:2805 process_output_block drivers/tty/n_tty.c:595 [inline] n_tty_write+0x498/0x1030 drivers/tty/n_tty.c:2333 do_tty_write drivers/tty/tty_io.c:959 [inline] tty_write+0x342/0x770 drivers/tty/tty_io.c:1043 __vfs_write+0xdb/0x840 fs/read_write.c:480 vfs_write+0x150/0x4f0 fs/read_write.c:544 SYSC_write fs/read_write.c:590 [inline] SyS_write+0x100/0x250 fs/read_write.c:582 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x45de29 RSP: 002b:00007f667b457c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 000000000003a600 RCX: 000000000045de29 RDX: 0000000000001006 RSI: 0000000020000180 RDI: 0000000000000006 RBP: 000000000118bf60 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bf2c R13: 00007ffe966998cf R14: 00007f667b4589c0 R15: 000000000118bf2c Allocated by task 7206: 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 __do_kmalloc mm/slab.c:3720 [inline] __kmalloc+0x15d/0x410 mm/slab.c:3729 kmalloc include/linux/slab.h:493 [inline] kzalloc include/linux/slab.h:661 [inline] neigh_alloc net/core/neighbour.c:324 [inline] __neigh_create+0x1c2/0x1810 net/core/neighbour.c:499 ip6_finish_output2+0x7fd/0x2070 net/ipv6/ip6_output.c:117 ip6_finish_output+0x56d/0xa50 net/ipv6/ip6_output.c:154 NF_HOOK_COND include/linux/netfilter.h:239 [inline] ip6_output+0x1b3/0x610 net/ipv6/ip6_output.c:171 dst_output include/net/dst.h:470 [inline] NF_HOOK include/linux/netfilter.h:250 [inline] mld_sendpack+0x635/0xe10 net/ipv6/mcast.c:1660 mld_send_cr net/ipv6/mcast.c:1956 [inline] mld_ifc_timer_expire+0x361/0x720 net/ipv6/mcast.c:2455 call_timer_fn+0x142/0x570 kernel/time/timer.c:1280 expire_timers+0x299/0x440 kernel/time/timer.c:1319 __run_timers kernel/time/timer.c:1637 [inline] run_timer_softirq+0x1cd/0x540 kernel/time/timer.c:1650 __do_softirq+0x246/0x9b5 kernel/softirq.c:288 Freed by task 0: (stack is not available) The buggy address belongs to the object at ffff8881d4d63240 which belongs to the cache kmalloc-1024 of size 1024 The buggy address is located 126 bytes to the right of 1024-byte region [ffff8881d4d63240, ffff8881d4d63640) The buggy address belongs to the page: page:ffffea0007535880 count:1 mapcount:0 mapping:ffff8881d4d62040 index:0x0 compound_mapcount: 0 flags: 0x17ffe0000008100(slab|head) raw: 017ffe0000008100 ffff8881d4d62040 0000000000000000 0000000100000007 raw: ffffea00075430a0 ffffea0007582520 ffff8881f6000ac0 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8881d4d63580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8881d4d63600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff8881d4d63680: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ^ ffff8881d4d63700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881d4d63780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================