KASAN: null-ptr-deref Read in do_con

KASAN: null-ptr-deref Read in do_con_trol
Status: upstream: reported C repro on 2020/02/13 18:37
Reported-by: syzbot+70b2d05eec48639a904e@syzkaller.appspotmail.com
First crash: 105d, last: 42d

Cause bisection: the bug happens on the oldest tested release
Crash: WARNING in sysfs_warn_dup (log)
Repro: C syz .config

Fix bisection: failed (bisect log)

similar bugs (2):
Kernel	Title	Repro	Bisected	Count	Last	Reported	Patched	Status
linux-4.19	KASAN: null-ptr-deref Read in do_con_trol	C		1	14d	104d	0/1	upstream: reported C repro on 2020/02/14 08:22
linux-4.14	KASAN: null-ptr-deref Read in do_con_trol	C		1	13d	104d	0/1	upstream: reported C repro on 2020/02/15 00:04

Sample crash report:

==================================================================
BUG: KASAN: null-ptr-deref in memcpy include/linux/string.h:381 [inline]
BUG: KASAN: null-ptr-deref in scr_memcpyw include/linux/vt_buffer.h:49 [inline]
BUG: KASAN: null-ptr-deref in delete_char drivers/tty/vt/vt.c:852 [inline]
BUG: KASAN: null-ptr-deref in csi_P drivers/tty/vt/vt.c:1985 [inline]
BUG: KASAN: null-ptr-deref in do_con_trol+0x3b9/0x61b0 drivers/tty/vt/vt.c:2379
Read of size 4294967294 at addr 0000000000000012 by task syz-executor031/10979

CPU: 1 PID: 10979 Comm: syz-executor031 Not tainted 5.6.0-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+0x197/0x210 lib/dump_stack.c:118
 __kasan_report.cold+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+0x134/0x1a0 mm/kasan/generic.c:192
 memcpy+0x24/0x50 mm/kasan/common.c:127
 memcpy include/linux/string.h:381 [inline]
 scr_memcpyw include/linux/vt_buffer.h:49 [inline]
 delete_char drivers/tty/vt/vt.c:852 [inline]
 csi_P drivers/tty/vt/vt.c:1985 [inline]
 do_con_trol+0x3b9/0x61b0 drivers/tty/vt/vt.c:2379
 do_con_write.part.0+0xfd9/0x1ef0 drivers/tty/vt/vt.c:2797
 do_con_write drivers/tty/vt/vt.c:2565 [inline]
 con_write+0x46/0xd0 drivers/tty/vt/vt.c:3135
 process_output_block drivers/tty/n_tty.c:595 [inline]
 n_tty_write+0x40e/0x1080 drivers/tty/n_tty.c:2333
 do_tty_write drivers/tty/tty_io.c:962 [inline]
 tty_write+0x496/0x7f0 drivers/tty/tty_io.c:1046
 __vfs_write+0x8a/0x110 fs/read_write.c:494
 vfs_write+0x268/0x5d0 fs/read_write.c:558
 ksys_write+0x14f/0x290 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x73/0xb0 fs/read_write.c:620
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 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:00007ffe661a6468 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004404f9
RDX: 0000000000000078 RSI: 0000000020000140 RDI: 0000000000000004
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401de0
R13: 0000000000401e70 R14: 0000000000000000 R15: 0000000000000000
==================================================================

Crashes (6):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	Maintainers
ci-upstream-kasan-gce-selinux-root	2020/02/16 02:20	upstream	829e6944	5d7b90f1	.config	log	report	syz	C	b.zolnierkie@samsung.com, daniel.vetter@ffwll.ch, ghalat@redhat.com, gregkh@linuxfoundation.org, jslaby@suse.com, linux-kernel@vger.kernel.org, lukas@wunner.de, okash.khawaja@gmail.com, oleksandr@redhat.com, sam@ravnborg.org
ci-upstream-kasan-gce-root	2020/02/14 18:36	upstream	b19e8c68	5d7b90f1	.config	log	report	syz	C	daniel.vetter@ffwll.ch, ghalat@redhat.com, gregkh@linuxfoundation.org, jslaby@suse.com, linux-kernel@vger.kernel.org, lukas@wunner.de, maarten.lankhorst@linux.intel.com, okash.khawaja@gmail.com, oleksandr@redhat.com, sam@ravnborg.org
ci-upstream-kasan-gce	2020/02/13 08:32	upstream	f2850dd5	84f4fc8a	.config	log	report	syz	C	daniel.vetter@ffwll.ch, ghalat@redhat.com, gregkh@linuxfoundation.org, jslaby@suse.com, linux-kernel@vger.kernel.org, lukas@wunner.de, okash.khawaja@gmail.com, oleksandr@redhat.com, sam@ravnborg.org
ci-upstream-kasan-gce-386	2020/02/13 08:41	upstream	f2850dd5	84f4fc8a	.config	log	report	syz	C	daniel.vetter@ffwll.ch, ghalat@redhat.com, gregkh@linuxfoundation.org, jslaby@suse.com, linux-kernel@vger.kernel.org, lukas@wunner.de, okash.khawaja@gmail.com, oleksandr@redhat.com, sam@ravnborg.org
ci-upstream-linux-next-kasan-gce-root	2020/02/13 07:53	linux-next	51d5d207	84f4fc8a	.config	log	report	syz	C	daniel.vetter@ffwll.ch, ghalat@redhat.com, gregkh@linuxfoundation.org, jslaby@suse.com, linux-kernel@vger.kernel.org, lukas@wunner.de, maarten.lankhorst@linux.intel.com, nico@fluxnic.net, okash.khawaja@gmail.com, sam@ravnborg.org
ci-upstream-linux-next-kasan-gce-root	2020/02/13 05:16	linux-next	51d5d207	84f4fc8a	.config	log	report			b.zolnierkie@samsung.com, daniel.vetter@ffwll.ch, ghalat@redhat.com, gregkh@linuxfoundation.org, jslaby@suse.com, linux-kernel@vger.kernel.org, lukas@wunner.de, nico@fluxnic.net, okash.khawaja@gmail.com, sam@ravnborg.org