KMSAN: kernel-infoleak in vcs

KMSAN: kernel-infoleak in vcs_read (2)
Status: upstream: reported on 2019/12/04 15:25
Reported-by: syzbot+31a641689d43387f05d3@syzkaller.appspotmail.com
First crash: 79d, last: 13d

similar bugs (1):
Kernel	Title	Repro	Bisected	Count	Last	Reported	Patched	Status
upstream	KMSAN: kernel-infoleak in vcs_read	C		531	613d	623d	9/17	fixed on 2018/07/13 11:20

Sample crash report:

=====================================================
BUG: KMSAN: kernel-infoleak in kmsan_copy_to_user+0x81/0x90 mm/kmsan/kmsan_hooks.c:253
CPU: 1 PID: 22975 Comm: syz-executor.0 Not tainted 5.5.0-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+0x1c9/0x220 lib/dump_stack.c:118
 kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:118
 kmsan_internal_check_memory+0x19d/0x3d0 mm/kmsan/kmsan.c:443
 kmsan_copy_to_user+0x81/0x90 mm/kmsan/kmsan_hooks.c:253
 _copy_to_user+0x15a/0x1f0 lib/usercopy.c:33
 copy_to_user include/linux/uaccess.h:174 [inline]
 vcs_read+0x17db/0x2340 drivers/tty/vt/vc_screen.c:424
 __vfs_read+0x1a9/0xc80 fs/read_write.c:425
 vfs_read+0x346/0x6a0 fs/read_write.c:461
 ksys_read+0x267/0x450 fs/read_write.c:587
 __do_sys_read fs/read_write.c:597 [inline]
 __se_sys_read+0x92/0xb0 fs/read_write.c:595
 __x64_sys_read+0x4a/0x70 fs/read_write.c:595
 do_syscall_64+0xb8/0x160 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45b399
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:00007f58e3590c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f58e35916d4 RCX: 000000000045b399
RDX: 0000000000001000 RSI: 00000000200004c0 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000086b R14: 00000000004c9da2 R15: 000000000075bf2c

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:144 [inline]
 kmsan_internal_chain_origin+0xad/0x130 mm/kmsan/kmsan.c:310
 kmsan_memcpy_memmove_metadata+0x272/0x2e0 mm/kmsan/kmsan.c:247
 kmsan_memcpy_metadata+0xb/0x10 mm/kmsan/kmsan.c:267
 __msan_memcpy+0x43/0x50 mm/kmsan/kmsan_instr.c:116
 vc_uniscr_copy_line+0x49b/0x730 drivers/tty/vt/vt.c:566
 vcs_read+0xc72/0x2340 drivers/tty/vt/vc_screen.c:332
 __vfs_read+0x1a9/0xc80 fs/read_write.c:425
 vfs_read+0x346/0x6a0 fs/read_write.c:461
 ksys_read+0x267/0x450 fs/read_write.c:587
 __do_sys_read fs/read_write.c:597 [inline]
 __se_sys_read+0x92/0xb0 fs/read_write.c:595
 __x64_sys_read+0x4a/0x70 fs/read_write.c:595
 do_syscall_64+0xb8/0x160 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:144 [inline]
 kmsan_internal_poison_shadow+0x66/0xd0 mm/kmsan/kmsan.c:127
 kmsan_slab_alloc+0x8a/0xe0 mm/kmsan/kmsan_hooks.c:82
 slab_alloc_node mm/slub.c:2774 [inline]
 slab_alloc mm/slub.c:2783 [inline]
 __kmalloc+0x2ad/0x450 mm/slub.c:3816
 kmalloc include/linux/slab.h:561 [inline]
 vc_uniscr_alloc+0x95/0x730 drivers/tty/vt/vt.c:353
 vc_do_resize+0x5e7/0x2bd0 drivers/tty/vt/vt.c:1192
 vt_resize+0x10e/0x170 drivers/tty/vt/vt.c:1325
 tty_ioctl+0x2ad7/0x2f00 drivers/tty/tty_io.c:2506
 do_vfs_ioctl+0xd88/0x3060 fs/ioctl.c:47
 ksys_ioctl fs/ioctl.c:749 [inline]
 __do_sys_ioctl fs/ioctl.c:756 [inline]
 __se_sys_ioctl+0x1da/0x270 fs/ioctl.c:754
 __x64_sys_ioctl+0x4a/0x70 fs/ioctl.c:754
 do_syscall_64+0xb8/0x160 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Bytes 0-319 of 640 are uninitialized
Memory access of size 640 starts at ffff8a2394c6d000
Data copied to user address 00000000200004c0
=====================================================

Crashes (8):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Maintainers
ci-upstream-kmsan-gce	2020/02/08 22:29	https://github.com/google/kmsan.git master	686a4f77	06150bf1	.config	log	report	gregkh@linuxfoundation.org, jslaby@suse.com, jwilk@jwilk.net, linux-kernel@vger.kernel.org, nico@fluxnic.net
ci-upstream-kmsan-gce	2020/02/08 11:25	https://github.com/google/kmsan.git master	686a4f77	06150bf1	.config	log	report	gregkh@linuxfoundation.org, jslaby@suse.com, jwilk@jwilk.net, linux-kernel@vger.kernel.org, nico@fluxnic.net
ci-upstream-kmsan-gce	2020/01/29 17:28	https://github.com/google/kmsan.git master	686a4f77	5ed23f9a	.config	log	report	gregkh@linuxfoundation.org, jslaby@suse.com, jwilk@jwilk.net, linux-kernel@vger.kernel.org, nico@fluxnic.net
ci-upstream-kmsan-gce	2020/01/29 16:08	https://github.com/google/kmsan.git master	686a4f77	5ed23f9a	.config	log	report	gregkh@linuxfoundation.org, jslaby@suse.com, jwilk@jwilk.net, linux-kernel@vger.kernel.org, nico@fluxnic.net
ci-upstream-kmsan-gce	2020/01/15 16:22	https://github.com/google/kmsan.git master	686a4f77	069a5a44	.config	log	report	gregkh@linuxfoundation.org, jslaby@suse.com, jwilk@jwilk.net, linux-kernel@vger.kernel.org, nico@fluxnic.net
ci-upstream-kmsan-gce	2020/01/03 10:40	https://github.com/google/kmsan.git master	997a8b55	9dcc1191	.config	log	report	gregkh@linuxfoundation.org, jslaby@suse.com, jwilk@jwilk.net, linux-kernel@vger.kernel.org, nico@fluxnic.net
ci-upstream-kmsan-gce	2019/12/29 03:35	https://github.com/google/kmsan.git master	997a8b55	af6b8ef8	.config	log	report	gregkh@linuxfoundation.org, jslaby@suse.com, jwilk@jwilk.net, linux-kernel@vger.kernel.org, nico@fluxnic.net
ci-upstream-kmsan-gce	2019/12/04 14:52	https://github.com/google/kmsan.git master	141b13f7	b2088328	.config	log	report	gregkh@linuxfoundation.org, jslaby@suse.com, jwilk@jwilk.net, linux-kernel@vger.kernel.org, nico@fluxnic.net