KASAN: null-ptr-deref Read in insert_char

Status: fixed on 2020/08/11 22:51
Reported-by: syzbot+6e01a57250c3eb4eb8ff@syzkaller.appspotmail.com
Fix commit: ce684552a266 vt: Reject zero-sized screen buffer size.
First crash: 2418d, last: 2223d
Fix bisection: fixed by (bisect log) :
commit 74752b81eae8ae64e97de222320026367e92c4b5
Author: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Sun Jul 12 11:10:12 2020 +0000

  vt: Reject zero-sized screen buffer size.

  
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.14 KASAN: null-ptr-deref Read in insert_char 11 syz, C inconclusive 1 2258d 2408d 0/1 upstream: reported C repro on 2020/01/09 20:28
upstream KASAN: null-ptr-deref Read in insert_char serial 11 syz, C done error 12 2281d 2409d 0/29 closed as dup on 2020/08/16 01:43
▶ ▼ Fix bisection attempts (7)
Created Duration User Patch Repo Result
2020/08/11 16:07 3h29m bisect fix linux-4.19.y OK (1) job log
2020/07/12 15:43 24m bisect fix linux-4.19.y OK (0) job log log
2020/06/12 15:17 26m bisect fix linux-4.19.y OK (0) job log log
2020/05/13 14:48 28m bisect fix linux-4.19.y OK (0) job log log
2020/04/13 14:23 25m bisect fix linux-4.19.y OK (0) job log log
2020/03/14 13:55 27m bisect fix linux-4.19.y OK (0) job log log
2020/02/08 09:46 25m bisect fix linux-4.19.y OK (0) job log log

Sample crash report:
audit: type=1400 audit(1578562314.351:36): avc:  denied  { map } for  pid=8008 comm="syz-executor864" path="/root/syz-executor864159292" dev="sda1" ino=16484 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
==================================================================
BUG: KASAN: null-ptr-deref in memmove include/linux/string.h:363 [inline]
BUG: KASAN: null-ptr-deref in scr_memmovew include/linux/vt_buffer.h:68 [inline]
BUG: KASAN: null-ptr-deref in insert_char+0x206/0x450 drivers/tty/vt/vt.c:839
Read of size 4294967294 at addr 0000000000000010 by task syz-executor864/8008

CPU: 1 PID: 8008 Comm: syz-executor864 Not tainted 4.19.93-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+0x197/0x210 lib/dump_stack.c:118
 kasan_report_error mm/kasan/report.c:352 [inline]
 kasan_report mm/kasan/report.c:412 [inline]
 kasan_report.cold+0x199/0x2ba mm/kasan/report.c:396
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x123/0x190 mm/kasan/kasan.c:267
 memmove+0x24/0x50 mm/kasan/kasan.c:293
 memmove include/linux/string.h:363 [inline]
 scr_memmovew include/linux/vt_buffer.h:68 [inline]
 insert_char+0x206/0x450 drivers/tty/vt/vt.c:839
 csi_at drivers/tty/vt/vt.c:1965 [inline]
 do_con_trol+0x3ca8/0x6070 drivers/tty/vt/vt.c:2412
 do_con_write.part.0+0xfd5/0x1eb0 drivers/tty/vt/vt.c:2773
 do_con_write drivers/tty/vt/vt.c:2541 [inline]
 con_write+0x46/0xd0 drivers/tty/vt/vt.c:3110
 process_output_block drivers/tty/n_tty.c:593 [inline]
 n_tty_write+0x3f9/0x1140 drivers/tty/n_tty.c:2331
 do_tty_write drivers/tty/tty_io.c:960 [inline]
 tty_write+0x458/0x7a0 drivers/tty/tty_io.c:1044
 __vfs_write+0x114/0x810 fs/read_write.c:485
 vfs_write+0x20c/0x560 fs/read_write.c:549
 ksys_write+0x14f/0x2d0 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+0x73/0xb0 fs/read_write.c:608
 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4404f9
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 0f 83 5b 14 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fff1e748358 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004404f9
RDX: 0000000000000078 RSI: 0000000020000000 RDI: 0000000000000004
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401de0
R13: 0000000000401e70 R14: 0000000000000000 R15: 0000000000000000
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/01/09 09:34 linux-4.19.y 3d40d7117e35 ddc3e859 .config console log report syz C ci2-linux-4-19
2020/02/13 13:55 linux-4.19.y 357668399cf7 e6247653 .config console log report ci2-linux-4-19
2019/12/30 16:35 linux-4.19.y 672481c2deff 6b36d338 .config console log report ci2-linux-4-19
* Struck through repros no longer work on HEAD.