bisecting fixing commit since 6794862a16ef41f753abd75c03a152836e4c8028
building syzkaller on 101194ebf6834198300032f6fb438f2c4cdf0401
testing commit 6794862a16ef41f753abd75c03a152836e4c8028 with gcc (GCC) 8.1.0
kernel signature: a3f1859bfc59b64072edc7e507f2eee9f30d84510cd5acdaa73d5e8914fcba7b
all runs: crashed: KASAN: user-memory-access Read in insert_char
testing current HEAD 9786cab674574239b04df638f825ee0e7d76a48c
testing commit 9786cab674574239b04df638f825ee0e7d76a48c with gcc (GCC) 8.1.0
kernel signature: 66c2cd61e911b4f70723e38a3336799cd8318febee6ba945bffdd33a6fc379de
all runs: crashed: KASAN: user-memory-access Read in insert_char
revisions tested: 2, total time: 19m3.069582331s (build: 11m50.480207603s, test: 6m41.880057215s)
the crash still happens on HEAD
commit msg: Merge tag 'selinux-pr-20200416' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux
crash: KASAN: user-memory-access Read in insert_char
==================================================================
BUG: KASAN: user-memory-access in memmove include/linux/string.h:396 [inline]
BUG: KASAN: user-memory-access in scr_memmovew include/linux/vt_buffer.h:68 [inline]
BUG: KASAN: user-memory-access in insert_char+0x1e2/0x3e0 drivers/tty/vt/vt.c:839
Read of size 212 at addr 00000000ffffff3a by task syz-executor.1/8023

CPU: 1 PID: 8023 Comm: syz-executor.1 Not tainted 5.7.0-rc1-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+0x5/0x4e 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:839
 csi_at drivers/tty/vt/vt.c:1986 [inline]
 do_con_trol+0x5742/0x63d0 drivers/tty/vt/vt.c:2453
 do_con_write.part.25+0xaa9/0x1ac0 drivers/tty/vt/vt.c:2817
 do_con_write drivers/tty/vt/vt.c:2587 [inline]
 con_write+0x1f/0x80 drivers/tty/vt/vt.c:3153
 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: 0033:0x45a849
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:00007f74a0c12c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a849
RDX: 0000000000000078 RSI: 0000000020000000 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f74a0c136d4
R13: 00000000004cbd0f R14: 00000000004e59d8 R15: 00000000ffffffff
==================================================================