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KMSAN: uninit-value in vcs_read

Status: fixed on 2018/11/09 05:44
Subsystems: serial
[Documentation on labels]
Reported-by: syzbot+fed4435f163beccc67eb@syzkaller.appspotmail.com
Fix commit: 21eff69aaaa0 vt: prevent leaking uninitialized data to userspace via /dev/vcs*
First crash: 2383d, last: 2321d
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
KMSAN: uninit-value in vcs_read 2 (4) 2018/11/08 16:56
▶ ▼ Similar bugs (1)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KMSAN: uninit-value in vcs_read (2) serial 1 1549d 1545d 0/28 auto-closed as invalid on 2020/11/15 18:12

Sample crash report:
==================================================================
BUG: KMSAN: uninit-value in copy_to_user include/linux/uaccess.h:184 [inline]
BUG: KMSAN: uninit-value in vcs_read+0x18ba/0x1cc0 drivers/tty/vt/vc_screen.c:352
CPU: 0 PID: 4513 Comm: syz-executor273 Not tainted 4.16.0+ #87
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x185/0x1d0 lib/dump_stack.c:53
 kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
 kmsan_internal_check_memory+0x174/0x1e0 mm/kmsan/kmsan.c:1176
 kmsan_copy_to_user+0x69/0x160 mm/kmsan/kmsan.c:1199
 copy_to_user include/linux/uaccess.h:184 [inline]
 vcs_read+0x18ba/0x1cc0 drivers/tty/vt/vc_screen.c:352
 do_loop_readv_writev fs/read_write.c:673 [inline]
 do_iter_read+0x880/0xd70 fs/read_write.c:897
 vfs_readv fs/read_write.c:959 [inline]
 do_preadv+0x3a1/0x580 fs/read_write.c:1043
 SYSC_preadv+0xc6/0xe0 fs/read_write.c:1093
 SyS_preadv+0x77/0xa0 fs/read_write.c:1088
 do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x4491e9
RSP: 002b:00007f7f4909bda8 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 00000000006dac24 RCX: 00000000004491e9
RDX: 0000000000000002 RSI: 0000000020000540 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dac20
R13: 7363762f7665642f R14: 00007f7f4909c9c0 R15: 0000000000000001

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
 kmsan_save_stack mm/kmsan/kmsan.c:293 [inline]
 kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:684
 __msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:528
 vcs_read+0x17a3/0x1cc0 drivers/tty/vt/vc_screen.c:333
 do_loop_readv_writev fs/read_write.c:673 [inline]
 do_iter_read+0x880/0xd70 fs/read_write.c:897
 vfs_readv fs/read_write.c:959 [inline]
 do_preadv+0x3a1/0x580 fs/read_write.c:1043
 SYSC_preadv+0xc6/0xe0 fs/read_write.c:1093
 SyS_preadv+0x77/0xa0 fs/read_write.c:1088
 do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x3d/0xa2
Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
 kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:188
 kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:314
 __kmalloc+0x23c/0x350 mm/slub.c:3791
 kmalloc include/linux/slab.h:517 [inline]
 vc_allocate+0x438/0x800 drivers/tty/vt/vt.c:787
 con_install+0x8c/0x640 drivers/tty/vt/vt.c:2876
 tty_driver_install_tty drivers/tty/tty_io.c:1224 [inline]
 tty_init_dev+0x1b0/0x1020 drivers/tty/tty_io.c:1324
 tty_open_by_driver drivers/tty/tty_io.c:1959 [inline]
 tty_open+0x15e9/0x2ea0 drivers/tty/tty_io.c:2007
 chrdev_open+0xc20/0xd90 fs/char_dev.c:417
 do_dentry_open+0xcc6/0x1430 fs/open.c:752
 vfs_open+0x1b7/0x2e0 fs/open.c:866
 do_last fs/namei.c:3379 [inline]
 path_openat+0x481d/0x6610 fs/namei.c:3520
 do_filp_open+0x261/0x640 fs/namei.c:3554
 do_sys_open+0x624/0x960 fs/open.c:1059
 SYSC_open+0xab/0xc0 fs/open.c:1077
 SyS_open+0x54/0x80 fs/open.c:1072
 do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x3d/0xa2

Bytes 4-8 of 9 are uninitialized
==================================================================

Crashes (2343):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2018/04/25 20:06 https://github.com/google/kmsan.git master d2d741e5d189 73417389 .config console log report syz C ci-upstream-kmsan-gce
2018/04/07 17:04 https://github.com/google/kmsan.git master e2ab7e8abba4 66f22a7f .config console log report syz C ci-upstream-kmsan-gce
2018/06/08 11:21 https://github.com/google/kmsan.git master c6a6aed994b6 f7b27b7a .config console log report ci-upstream-kmsan-gce
2018/06/08 10:06 https://github.com/google/kmsan.git master c6a6aed994b6 f7b27b7a .config console log report ci-upstream-kmsan-gce
2018/06/08 01:51 https://github.com/google/kmsan.git master c6a6aed994b6 645e75f8 .config console log report ci-upstream-kmsan-gce
2018/06/08 00:20 https://github.com/google/kmsan.git master c6a6aed994b6 645e75f8 .config console log report ci-upstream-kmsan-gce
2018/06/07 22:02 https://github.com/google/kmsan.git master c6a6aed994b6 645e75f8 .config console log report ci-upstream-kmsan-gce
2018/06/07 17:37 https://github.com/google/kmsan.git master c6a6aed994b6 645e75f8 .config console log report ci-upstream-kmsan-gce
2018/06/07 05:33 https://github.com/google/kmsan.git master b9a5d319699c e0e534c6 .config console log report ci-upstream-kmsan-gce
2018/06/07 04:33 https://github.com/google/kmsan.git master b9a5d319699c e0e534c6 .config console log report ci-upstream-kmsan-gce
2018/06/06 23:40 https://github.com/google/kmsan.git master b9a5d319699c e0e534c6 .config console log report ci-upstream-kmsan-gce
2018/06/06 18:00 https://github.com/google/kmsan.git master b9a5d319699c 41f9540d .config console log report ci-upstream-kmsan-gce
2018/06/06 15:23 https://github.com/google/kmsan.git master 8fc8ecd1c58a 41f9540d .config console log report ci-upstream-kmsan-gce
2018/06/06 10:56 https://github.com/google/kmsan.git master 8fc8ecd1c58a 41f9540d .config console log report ci-upstream-kmsan-gce
2018/06/06 06:29 https://github.com/google/kmsan.git master 8fc8ecd1c58a 863a24bb .config console log report ci-upstream-kmsan-gce
2018/06/06 04:23 https://github.com/google/kmsan.git master 8fc8ecd1c58a 863a24bb .config console log report ci-upstream-kmsan-gce
2018/06/06 01:08 https://github.com/google/kmsan.git master 8fc8ecd1c58a 863a24bb .config console log report ci-upstream-kmsan-gce
2018/06/05 23:30 https://github.com/google/kmsan.git master 8fc8ecd1c58a 863a24bb .config console log report ci-upstream-kmsan-gce
2018/06/05 18:06 https://github.com/google/kmsan.git master 8fc8ecd1c58a a316ff92 .config console log report ci-upstream-kmsan-gce
2018/06/05 14:52 https://github.com/google/kmsan.git master 8fc8ecd1c58a a316ff92 .config console log report ci-upstream-kmsan-gce
2018/06/05 11:56 https://github.com/google/kmsan.git master 8fc8ecd1c58a a316ff92 .config console log report ci-upstream-kmsan-gce
2018/06/05 05:04 https://github.com/google/kmsan.git master 8fc8ecd1c58a a50d873b .config console log report ci-upstream-kmsan-gce
2018/06/05 03:10 https://github.com/google/kmsan.git master 8fc8ecd1c58a a50d873b .config console log report ci-upstream-kmsan-gce
2018/06/05 01:27 https://github.com/google/kmsan.git master 8fc8ecd1c58a a50d873b .config console log report ci-upstream-kmsan-gce
2018/06/04 22:44 https://github.com/google/kmsan.git master 8fc8ecd1c58a a50d873b .config console log report ci-upstream-kmsan-gce
2018/06/04 11:30 https://github.com/google/kmsan.git master 8fc8ecd1c58a 6cbe7c26 .config console log report ci-upstream-kmsan-gce
2018/06/04 10:05 https://github.com/google/kmsan.git master 8fc8ecd1c58a 6cbe7c26 .config console log report ci-upstream-kmsan-gce
2018/06/04 06:03 https://github.com/google/kmsan.git master 8fc8ecd1c58a 2f93b54f .config console log report ci-upstream-kmsan-gce
2018/06/03 16:10 https://github.com/google/kmsan.git master 8fc8ecd1c58a 2f93b54f .config console log report ci-upstream-kmsan-gce
2018/06/03 14:05 https://github.com/google/kmsan.git master 8fc8ecd1c58a 2f93b54f .config console log report ci-upstream-kmsan-gce
2018/06/03 12:03 https://github.com/google/kmsan.git master 8fc8ecd1c58a 2f93b54f .config console log report ci-upstream-kmsan-gce
2018/06/03 05:32 https://github.com/google/kmsan.git master 8fc8ecd1c58a 2f93b54f .config console log report ci-upstream-kmsan-gce
2018/06/02 20:28 https://github.com/google/kmsan.git master 8fc8ecd1c58a 2f93b54f .config console log report ci-upstream-kmsan-gce
2018/06/02 17:13 https://github.com/google/kmsan.git master 8fc8ecd1c58a 2f93b54f .config console log report ci-upstream-kmsan-gce
2018/06/02 07:22 https://github.com/google/kmsan.git master 8fc8ecd1c58a 2f93b54f .config console log report ci-upstream-kmsan-gce
2018/06/02 03:34 https://github.com/google/kmsan.git master 8fc8ecd1c58a 2f93b54f .config console log report ci-upstream-kmsan-gce
2018/06/01 23:52 https://github.com/google/kmsan.git master 8fc8ecd1c58a 2f93b54f .config console log report ci-upstream-kmsan-gce
2018/06/01 21:30 https://github.com/google/kmsan.git master 8fc8ecd1c58a 2f93b54f .config console log report ci-upstream-kmsan-gce
2018/06/01 15:25 https://github.com/google/kmsan.git master 8fc8ecd1c58a 2f93b54f .config console log report ci-upstream-kmsan-gce
2018/06/01 08:06 https://github.com/google/kmsan.git master 8fc8ecd1c58a 2f93b54f .config console log report ci-upstream-kmsan-gce
2018/06/01 02:50 https://github.com/google/kmsan.git master 8fc8ecd1c58a 2f93b54f .config console log report ci-upstream-kmsan-gce
2018/05/31 22:39 https://github.com/google/kmsan.git master 8fc8ecd1c58a 2f93b54f .config console log report ci-upstream-kmsan-gce
2018/05/31 17:13 https://github.com/google/kmsan.git master 8fc8ecd1c58a 2f93b54f .config console log report ci-upstream-kmsan-gce
2018/04/06 22:20 https://github.com/google/kmsan.git master e2ab7e8abba4 d613535f .config console log report ci-upstream-kmsan-gce
* Struck through repros no longer work on HEAD.