bisecting fixing commit since 6794862a16ef41f753abd75c03a152836e4c8028
building syzkaller on 5a5826a14e99564bdd4de163d3ac368056e5d992
testing commit 6794862a16ef41f753abd75c03a152836e4c8028 with gcc (GCC) 8.1.0
kernel signature: 49fa083bf2cb775e8c05d5a7bda8bd588f88de0531d3990ca29b3a4bada1bcf6
all runs: crashed: KASAN: wild-memory-access Read in insert_char
testing current HEAD fb33c6510d5595144d585aa194d377cf74d31911
testing commit fb33c6510d5595144d585aa194d377cf74d31911 with gcc (GCC) 8.1.0
kernel signature: 503beeee0ccba1c28c4d3c59e0cb0cf68b5a28df8a4a8cccc8696bf304b61fb5
all runs: crashed: KASAN: wild-memory-access Read in insert_char
revisions tested: 2, total time: 21m43.018547485s (build: 12m47.659569668s, test: 8m22.4242739s)
the crash still happens on HEAD
commit msg: Linux 5.6-rc6
crash: KASAN: wild-memory-access Read in insert_char
==================================================================
BUG: KASAN: wild-memory-access in memmove include/linux/string.h:396 [inline]
BUG: KASAN: wild-memory-access in scr_memmovew include/linux/vt_buffer.h:68 [inline]
BUG: KASAN: wild-memory-access in insert_char+0x1e2/0x3e0 drivers/tty/vt/vt.c:839
Read of size 212 at addr 00000000ffffff3a by task syz-executor.2/7934

CPU: 1 PID: 7934 Comm: syz-executor.2 Not tainted 5.6.0-rc6-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+0x5/0x32 mm/kasan/report.c:510
 kasan_report+0x12/0x20 mm/kasan/common.c:641
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x153/0x1d0 mm/kasan/generic.c:192
 memmove+0x23/0x50 mm/kasan/common.c:117
 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:839
 csi_at drivers/tty/vt/vt.c:1975 [inline]
 do_con_trol+0x5742/0x63d0 drivers/tty/vt/vt.c:2442
 do_con_write.part.25+0xab6/0x1ad0 drivers/tty/vt/vt.c:2808
 do_con_write drivers/tty/vt/vt.c:2576 [inline]
 con_write+0x1f/0x80 drivers/tty/vt/vt.c:3144
 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+0x371/0x7d0 drivers/tty/tty_io.c:1046
 __vfs_write+0x5e/0x110 fs/read_write.c:494
 vfs_write+0x18a/0x520 fs/read_write.c:558
 ksys_write+0x105/0x220 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __ia32_sys_write+0x6c/0xa0 fs/read_write.c:620
 do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
 do_fast_syscall_32+0x235/0xbe0 arch/x86/entry/common.c:408
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7f4fe49
Code: 1d 00 00 00 89 d3 eb e0 8b 04 24 c3 8b 34 24 c3 8b 3c 24 c3 90 90 90 90 90 90 90 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000f7f4a0cc EFLAGS: 00000296 ORIG_RAX: 0000000000000004
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000020000000
RDX: 0000000000000078 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
==================================================================