bisecting fixing commit since b07f636fca1c8fbba124b0082487c0b3890a0e0c
building syzkaller on ddc3e85997efdad885e208db6a98bca86e5dd52f
testing commit b07f636fca1c8fbba124b0082487c0b3890a0e0c with gcc (GCC) 8.1.0
kernel signature: 33581cfbb8c724daf925784ae52ce32ca509c02e9e17bd732bccc0f73fd3ca36
all runs: crashed: KASAN: null-ptr-deref Read in insert_char
testing current HEAD 12bf0b632ed090358cbf03e323e5342212d0b2e4
testing commit 12bf0b632ed090358cbf03e323e5342212d0b2e4 with gcc (GCC) 8.1.0
kernel signature: 2c1500691eb4b40bf27f0ec833d1d881f3a7495aefb578df7434c04fedafda32
all runs: crashed: KASAN: null-ptr-deref Read in insert_char
revisions tested: 2, total time: 20m13.662651386s (build: 12m39.961496779s, test: 6m30.743152395s)
the crash still happens on HEAD
commit msg: Merge tag 'nfs-for-5.7-5' of git://git.linux-nfs.org/projects/trondmy/linux-nfs
crash: KASAN: null-ptr-deref Read in insert_char
==================================================================
BUG: KASAN: null-ptr-deref in memmove include/linux/string.h:396 [inline]
BUG: KASAN: null-ptr-deref in scr_memmovew include/linux/vt_buffer.h:68 [inline]
BUG: KASAN: null-ptr-deref in insert_char+0x1e2/0x3e0 drivers/tty/vt/vt.c:845
Read of size 4294967294 at addr 0000000000000010 by task syz-executor.0/8266

CPU: 0 PID: 8266 Comm: syz-executor.0 Not tainted 5.7.0-rc5-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+0x12d/0x187 lib/dump_stack.c:118
 __kasan_report.cold.11+0x5/0x3a mm/kasan/report.c:515
 kasan_report+0x38/0x50 mm/kasan/common.c:625
 check_memory_region_inline mm/kasan/generic.c:187 [inline]
 check_memory_region+0x1cc/0x1f0 mm/kasan/generic.c:193
 memmove+0x23/0x60 mm/kasan/common.c:95
 memmove include/linux/string.h:396 [inline]
 scr_memmovew include/linux/vt_buffer.h:68 [inline]
 insert_char+0x1e2/0x3e0 drivers/tty/vt/vt.c:845
 csi_at drivers/tty/vt/vt.c:1992 [inline]
 do_con_trol+0x5730/0x63b0 drivers/tty/vt/vt.c:2459
 do_con_write.part.21+0xaa9/0x1ac0 drivers/tty/vt/vt.c:2823
 do_con_write drivers/tty/vt/vt.c:2593 [inline]
 con_write+0x1f/0x80 drivers/tty/vt/vt.c:3159
 process_output_block drivers/tty/n_tty.c:595 [inline]
 n_tty_write+0x494/0xfa0 drivers/tty/n_tty.c:2333
 do_tty_write drivers/tty/tty_io.c:962 [inline]
 tty_write+0x377/0x7e0 drivers/tty/tty_io.c:1046
 __vfs_write+0x5e/0x110 fs/read_write.c:495
 vfs_write+0x190/0x530 fs/read_write.c:559
 ksys_write+0x10b/0x220 fs/read_write.c:612
 __do_sys_write fs/read_write.c:624 [inline]
 __se_sys_write fs/read_write.c:621 [inline]
 __x64_sys_write+0x6e/0xb0 fs/read_write.c:621
 do_syscall_64+0xca/0x630 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45af49
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:00007efd1d068c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045af49
RDX: 0000000000000078 RSI: 0000000020000000 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007efd1d0696d4
R13: 00000000004cce19 R14: 00000000004e81c0 R15: 00000000ffffffff
==================================================================