KMSAN: uninit-value in soft

KMSAN: uninit-value in soft_cursor
Status: upstream: reported syz repro on 2020/08/20 04:56
Reported-by: syzbot+2741e4d93bff16ad8d4d@syzkaller.appspotmail.com
First crash: 44d, last: 44d

Patch testing requests:
Created	Duration	User	Patch	Repo	Result
2020/09/02 23:46	20m	dragonjetli@gmail.com		https://github.com/google/kmsan.git master	OK

Sample crash report:

=====================================================
BUG: KMSAN: uninit-value in soft_cursor+0xa89/0x13f0 drivers/video/fbdev/core/softcursor.c:61
CPU: 0 PID: 12272 Comm: syz-executor.2 Not tainted 5.8.0-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+0x21c/0x280 lib/dump_stack.c:118
 kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:121
 __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215
 soft_cursor+0xa89/0x13f0 drivers/video/fbdev/core/softcursor.c:61
 bit_cursor+0x38c6/0x3a40 drivers/video/fbdev/core/bitblit.c:386
 fbcon_cursor+0x195e/0x1a60 drivers/video/fbdev/core/fbcon.c:1411
 set_cursor drivers/tty/vt/vt.c:915 [inline]
 redraw_screen+0x28ee/0x2980 drivers/tty/vt/vt.c:1031
 vc_do_resize+0x36a8/0x38f0 drivers/tty/vt/vt.c:1314
 vc_resize+0xc3/0xe0 drivers/tty/vt/vt.c:1334
 fbcon_modechanged+0xdc1/0x1320 drivers/video/fbdev/core/fbcon.c:2990
 fbcon_update_vcs+0x86/0xa0 drivers/video/fbdev/core/fbcon.c:3048
 fb_set_var+0x1420/0x1850 drivers/video/fbdev/core/fbmem.c:1056
 do_fb_ioctl+0xc00/0x1150 drivers/video/fbdev/core/fbmem.c:1109
 fb_ioctl+0x1e4/0x210 drivers/video/fbdev/core/fbmem.c:1185
 vfs_ioctl fs/ioctl.c:48 [inline]
 ksys_ioctl fs/ioctl.c:753 [inline]
 __do_sys_ioctl fs/ioctl.c:762 [inline]
 __se_sys_ioctl+0x319/0x4d0 fs/ioctl.c:760
 __x64_sys_ioctl+0x4a/0x70 fs/ioctl.c:760
 do_syscall_64+0xad/0x160 arch/x86/entry/common.c:386
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45d239
Code: Bad RIP value.
RSP: 002b:00007ff9aafacc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000000d580 RCX: 000000000045d239
RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003
RBP: 000000000118cf80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cf4c
R13: 000000000169fb6f R14: 00007ff9aafad9c0 R15: 000000000118cf4c

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
 soft_cursor+0x44d/0x13f0 drivers/video/fbdev/core/softcursor.c:50
 bit_cursor+0x38c6/0x3a40 drivers/video/fbdev/core/bitblit.c:386
 fbcon_cursor+0x195e/0x1a60 drivers/video/fbdev/core/fbcon.c:1411
 set_cursor drivers/tty/vt/vt.c:915 [inline]
 redraw_screen+0x28ee/0x2980 drivers/tty/vt/vt.c:1031
 vc_do_resize+0x36a8/0x38f0 drivers/tty/vt/vt.c:1314
 vc_resize+0xc3/0xe0 drivers/tty/vt/vt.c:1334
 fbcon_modechanged+0xdc1/0x1320 drivers/video/fbdev/core/fbcon.c:2990
 fbcon_update_vcs+0x86/0xa0 drivers/video/fbdev/core/fbcon.c:3048
 fb_set_var+0x1420/0x1850 drivers/video/fbdev/core/fbmem.c:1056
 do_fb_ioctl+0xc00/0x1150 drivers/video/fbdev/core/fbmem.c:1109
 fb_ioctl+0x1e4/0x210 drivers/video/fbdev/core/fbmem.c:1185
 vfs_ioctl fs/ioctl.c:48 [inline]
 ksys_ioctl fs/ioctl.c:753 [inline]
 __do_sys_ioctl fs/ioctl.c:762 [inline]
 __se_sys_ioctl+0x319/0x4d0 fs/ioctl.c:760
 __x64_sys_ioctl+0x4a/0x70 fs/ioctl.c:760
 do_syscall_64+0xad/0x160 arch/x86/entry/common.c:386
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Local variable ----cursor@bit_cursor created at:
 bit_cursor+0xe3/0x3a40 drivers/video/fbdev/core/bitblit.c:239
 bit_cursor+0xe3/0x3a40 drivers/video/fbdev/core/bitblit.c:239
=====================================================

Crashes (1):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Maintainers
ci-upstream-kmsan-gce	2020/08/15 19:32	https://github.com/google/kmsan.git master	ce8056d1	424dd8e7	.config	log	report	syz			b.zolnierkie@samsung.com, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org