FYI, we noticed the following commit (built with gcc-7):

commit: c1e0d2be0acff5e99a59ddcc5af415e48abc6c5e ("mt76: mmio: introduce mt76x02_check_tx_hang watchdog")
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master

in testcase: trinity
with following parameters:

	runtime: 300s

test-description: Trinity is a linux system call fuzz tester.
test-url: http://codemonkey.org.uk/projects/trinity/


on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 2G

caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):


+------------------------------------------------------------+------------+------------+
|                                                            | 87e86f9019 | c1e0d2be0a |
+------------------------------------------------------------+------------+------------+
| boot_successes                                             | 167        | 140        |
| boot_failures                                              | 0          | 23         |
| BUG:pagefault_on_kernel_address#in_non-whitelisted_uaccess | 0          | 23         |
| BUG:unable_to_handle_kernel                                | 0          | 23         |
| Oops:#[##]                                                 | 0          | 23         |
| RIP:strncpy_from_user                                      | 0          | 23         |
| Kernel_panic-not_syncing:Fatal_exception                   | 0          | 23         |
+------------------------------------------------------------+------------+------------+



[   10.383586] BUG: pagefault on kernel address 0xffff93d4b5cd8000 in non-whitelisted uaccess
[   10.390934] BUG: unable to handle kernel paging request at ffff93d4b5cd8000
[   10.390934] #PF error: [normal kernel read fault]
[   10.390934] PGD 21e00067 P4D 21e00067 PUD 21e04067 PMD 78b57067 PTE 800fffff8a327060
[   10.390934] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
[   10.390934] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G                T 5.0.0-rc1-00033-gc1e0d2b #1
[   10.390934] RIP: 0010:strncpy_from_user+0x87/0x10c
[   10.390934] Code: 00 00 66 66 90 4c 39 c2 48 bb ff fe fe fe fe fe fe fe 49 ba 80 80 80 80 80 80 80 80 4c 0f 46 c2 31 c0 45 31 db eb 4c 44 89 d9 <4c> 8b 0c 06 85 c9 74 05 45 31 d2 eb 61 49 8d 0c 19 4c 89 0c 07 49
[   10.390934] RSP: 0000:ffffbd8c00323bc0 EFLAGS: 00010206
[   10.390934] RAX: 0000000000000028 RBX: fefefefefefefeff RCX: 0000000000000000
[   10.390934] RDX: 0000000000000fe0 RSI: ffff93d4b5cd7fd6 RDI: ffff93d4af5e3020
[   10.390934] RBP: 00000000ffffff9c R08: 0000000000000fe0 R09: 8c93909d92868cd1
[   10.390934] R10: 8080808080808080 R11: 0000000000000000 R12: ffff93d4b5cd7fd6
[   10.390934] R13: ffff93d4b5cd7fd6 R14: 0000000000000000 R15: 0000000000000000
[   10.390934] FS:  0000000000000000(0000) GS:ffff93d4b6400000(0000) knlGS:0000000000000000
[   10.390934] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   10.390934] CR2: ffff93d4b5cd8000 CR3: 0000000020c15000 CR4: 00000000000006e0
[   10.390934] Call Trace:
[   10.390934]  ? getname_flags+0x6f/0x199
[   10.390934]  ? user_path_at_empty+0x18/0x2f
[   10.390934]  ? vfs_statx+0x6d/0xb3
[   10.390934]  ? clean_path+0x5c/0x102
[   10.390934]  ? do_name+0xf4/0x40e
[   10.390934]  ? write_buffer+0x52/0x8a
[   10.390934]  ? flush_buffer+0xe7/0x140
[   10.390934]  ? initrd_load+0xa8/0xa8
[   10.390934]  ? __gunzip+0x53a/0x6b7
[   10.390934]  ? bunzip2+0x76a/0x76a
[   10.390934]  ? write_buffer+0x8a/0x8a
[   10.390934]  ? gunzip+0x39/0x3d
[   10.390934]  ? initrd_load+0xa8/0xa8
[   10.390934]  ? unpack_to_rootfs+0x1c6/0x3c6
[   10.390934]  ? initrd_load+0xa8/0xa8
[   10.390934]  ? populate_rootfs+0x94/0x213
[   10.390934]  ? clean_rootfs+0x23b/0x23b
[   10.390934]  ? do_one_initcall+0x61/0x12a
[   10.390934]  ? kernel_init_freeable+0x1a8/0x305
[   10.390934]  ? rest_init+0x13a/0x13a
[   10.390934]  ? kernel_init+0x5/0xeb
[   10.390934]  ? ret_from_fork+0x35/0x40
[   10.390934] Modules linked in:
[   10.390934] CR2: ffff93d4b5cd8000
[   10.390934] ---[ end trace 81b307b1a0dd06e6 ]---


To reproduce:

        # build kernel
	cd linux
	cp config-5.0.0-rc1-00033-gc1e0d2b .config
	make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 olddefconfig
	make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 prepare
	make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 modules_prepare
	make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 SHELL=/bin/bash
	make HOSTCC=gcc-7 CC=gcc-7 ARCH=x86_64 bzImage


        git clone https://github.com/intel/lkp-tests.git
        cd lkp-tests
        bin/lkp qemu -k <bzImage> job-script # job-script is attached in this email



Thanks,
Rong Chen