bisecting fixing commit since ad326970d25cc85128cd22d62398751ad072efff building syzkaller on fea47c014be7a00a32ab016b946c0a77f32c1f40 testing commit ad326970d25cc85128cd22d62398751ad072efff with gcc (GCC) 8.4.1 20210217 kernel signature: ece14b5cb2b2f0d2dae4156b105156fc03259f31ebac099b80ce8931b7697d44 run #0: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #1: crashed: KASAN: slab-out-of-bounds Read in soft_cursor 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 soft_cursor run #7: crashed: KASAN: slab-out-of-bounds Read in soft_cursor run #8: crashed: KASAN: slab-out-of-bounds Read in soft_cursor run #9: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #10: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #11: crashed: KASAN: slab-out-of-bounds Read in soft_cursor run #12: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #13: crashed: KASAN: slab-out-of-bounds Read in soft_cursor run #14: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #15: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #16: crashed: KASAN: slab-out-of-bounds Read in soft_cursor run #17: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #18: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #19: crashed: KASAN: slab-out-of-bounds Read in soft_cursor testing current HEAD 2034d6f0838e465dd8f120c4e946d8444b4bb5df testing commit 2034d6f0838e465dd8f120c4e946d8444b4bb5df with gcc (GCC) 8.4.1 20210217 kernel signature: 29c1eab6d42a9fc723553f7ac24e0d05e2d1b5e55f24ce66f663a25ce72ed106 run #0: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #1: crashed: KASAN: slab-out-of-bounds Read in soft_cursor run #2: crashed: KASAN: slab-out-of-bounds Read in bit_putcs run #3: crashed: KASAN: slab-out-of-bounds Read in soft_cursor run #4: crashed: KASAN: slab-out-of-bounds Read in soft_cursor run #5: crashed: KASAN: slab-out-of-bounds Read in soft_cursor 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: slab-out-of-bounds Read in soft_cursor run #9: crashed: KASAN: slab-out-of-bounds Read in bit_putcs revisions tested: 2, total time: 25m8.436489482s (build: 18m8.85492172s, test: 6m27.891554925s) the crash still happens on HEAD commit msg: Linux 4.19.184 crash: KASAN: slab-out-of-bounds Read in bit_putcs IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50 wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50 IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready ================================================================== BUG: KASAN: slab-out-of-bounds in __fb_pad_aligned_buffer include/linux/fb.h:674 [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+0x951/0xcc0 drivers/video/fbdev/core/bitblit.c:185 Read of size 1 at addr ffff8881d0c99afe by task syz-executor.4/7605 CPU: 1 PID: 7605 Comm: syz-executor.4 Not tainted 4.19.184-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/0x226 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 mm/kasan/report.c:412 [inline] kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:396 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430 __fb_pad_aligned_buffer include/linux/fb.h:674 [inline] bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline] bit_putcs+0x951/0xcc0 drivers/video/fbdev/core/bitblit.c:185 fbcon_putcs+0x302/0x5f0 drivers/video/fbdev/core/fbcon.c:1269 con_flush drivers/tty/vt/vt.c:2559 [inline] do_con_write.part.13+0xab5/0x1aa0 drivers/tty/vt/vt.c:2809 do_con_write drivers/tty/vt/vt.c:2578 [inline] con_write+0x1f/0x80 drivers/tty/vt/vt.c:3145 process_output_block drivers/tty/n_tty.c:593 [inline] n_tty_write+0x4a4/0x1050 drivers/tty/n_tty.c:2331 do_tty_write drivers/tty/tty_io.c:960 [inline] tty_write+0x342/0x770 drivers/tty/tty_io.c:1044 __vfs_write+0xe3/0x890 fs/read_write.c:485 vfs_write+0x150/0x4d0 fs/read_write.c:549 ksys_write+0x103/0x260 fs/read_write.c:599 __do_sys_write fs/read_write.c:611 [inline] __se_sys_write fs/read_write.c:608 [inline] __x64_sys_write+0x6e/0xb0 fs/read_write.c:608 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465849 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f12b6b77188 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 000000000055c050 RCX: 0000000000465849 RDX: 0000000000001006 RSI: 0000000020000180 RDI: 0000000000000006 RBP: 00000000004af675 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055c050 R13: 00007fff595b08af R14: 00007f12b6b77300 R15: 0000000000022000 Allocated by task 7546: 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 __do_kmalloc_node mm/slab.c:3689 [inline] __kmalloc_node_track_caller+0x50/0x70 mm/slab.c:3703 __kmalloc_reserve.isra.9+0x2c/0xc0 net/core/skbuff.c:137 __alloc_skb+0xd7/0x580 net/core/skbuff.c:205 alloc_skb include/linux/skbuff.h:995 [inline] netlink_alloc_large_skb net/netlink/af_netlink.c:1190 [inline] netlink_sendmsg+0x953/0xc60 net/netlink/af_netlink.c:1884 sock_sendmsg_nosec net/socket.c:622 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:632 ___sys_sendmsg+0x647/0x950 net/socket.c:2115 __sys_sendmsg+0xd9/0x180 net/socket.c:2153 __do_sys_sendmsg net/socket.c:2162 [inline] __se_sys_sendmsg net/socket.c:2160 [inline] __x64_sys_sendmsg+0x73/0xb0 net/socket.c:2160 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe Freed by task 7546: 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] kfree+0xcf/0x220 mm/slab.c:3822 skb_free_head+0x74/0x90 net/core/skbuff.c:563 skb_release_data+0x513/0x760 net/core/skbuff.c:583 skb_release_all+0x3d/0x50 net/core/skbuff.c:640 __kfree_skb net/core/skbuff.c:654 [inline] consume_skb+0x93/0x270 net/core/skbuff.c:714 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x44b/0x660 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x667/0xc60 net/netlink/af_netlink.c:1909 sock_sendmsg_nosec net/socket.c:622 [inline] sock_sendmsg+0xac/0xf0 net/socket.c:632 ___sys_sendmsg+0x647/0x950 net/socket.c:2115 __sys_sendmsg+0xd9/0x180 net/socket.c:2153 __do_sys_sendmsg net/socket.c:2162 [inline] __se_sys_sendmsg net/socket.c:2160 [inline] __x64_sys_sendmsg+0x73/0xb0 net/socket.c:2160 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 ffff8881d0c99680 which belongs to the cache kmalloc-1024 of size 1024 The buggy address is located 126 bytes to the right of 1024-byte region [ffff8881d0c99680, ffff8881d0c99a80) The buggy address belongs to the page: page:ffffea0007432600 count:1 mapcount:0 mapping:ffff8881f6000ac0 index:0x0 compound_mapcount: 0 flags: 0x17ffe0000008100(slab|head) raw: 017ffe0000008100 ffffea0007a17f08 ffffea0007a0d688 ffff8881f6000ac0 raw: 0000000000000000 ffff8881d0c98000 0000000100000007 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8881d0c99980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881d0c99a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8881d0c99a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ^ ffff8881d0c99b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881d0c99b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== IPv6: ADDRCONF(NETDEV_UP): wlan1: link is not ready IPv6: ADDRCONF(NETDEV_UP): wlan1: link is not ready wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50 wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50 wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50 wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50 IPv6: ADDRCONF(NETDEV_UP): wlan1: link is not ready IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50 wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50 IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50 wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50 IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready IPv6: ADDRCONF(NETDEV_UP): wlan1: link is not ready wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50 wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50 IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready