Message-ID: <20160512013851.GA21405@yexl-desktop>
Date:	Thu, 12 May 2016 09:38:51 +0800
From:	kernel test robot <xiaolong.ye@...el.com>
To:	Miklos Szeredi <mszeredi@...hat.com>
Cc:	Miklos Szeredi <mszeredi@...i.piliscsaba.szeredi.hu>,
	LKML <linux-kernel@...r.kernel.org>, lkp@...org
Subject: [lkp] [vfs] 58a94fa182: BUG: unable to handle kernel NULL pointer
 dereference at 0000000000000028

FYI, we noticed the following commit:

https://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git overlayfs-linus
commit 58a94fa1824f21e2e94be7caad8673a95df89d58 ("vfs: add vfs_select_inode() helper")

on test machine: vm-vp-2G: 4 threads qemu-system-x86_64 -enable-kvm -cpu Penryn with 2G memory

caused below changes:


[    1.017580] pci 0000:00:02.0: Video device with shadowed ROM at [mem 0x000c0000-0x000dffff]
[    1.019600] PCI: CLS 0 bytes, default 64
[    1.020644] Unpacking initramfs...
[    1.021788] BUG: unable to handle kernel NULL pointer dereference at 0000000000000028
[    1.023826] IP: [<ffffffff8121c450>] __mnt_want_write+0x10/0x70
[    1.025112] PGD 0 
[    1.025935] Oops: 0000 [#1] SMP 
[    1.026978] Modules linked in:
[    1.027923] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.6.0-rc7-00001-g58a94fa #1
[    1.029765] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014
[    1.031764] task: ffff880074028000 ti: ffff880074024000 task.ti: ffff880074024000
[    1.033586] RIP: 0010:[<ffffffff8121c450>]  [<ffffffff8121c450>] __mnt_want_write+0x10/0x70
[    1.035600] RSP: 0000:ffff880074027a50  EFLAGS: 00010282
[    1.036744] RAX: 0000000000000000 RBX: ffff880073e2df00 RCX: ffff880073b6b8c8
[    1.038094] RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
[    1.039447] RBP: ffff880074027a50 R08: ffff880073b160f8 R09: 0000000000000000
[    1.040803] R10: 0000000000000000 R11: ffff880073b160c0 R12: ffff880074bf3000
[    1.042161] R13: ffff880073b6b778 R14: ffff880074027b80 R15: ffff880073e2df10
[    1.043511] FS:  0000000000000000(0000) GS:ffff880077200000(0000) knlGS:0000000000000000
[    1.045417] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    1.046608] CR2: 0000000000000028 CR3: 0000000001e06000 CR4: 00000000000006f0
[    1.047961] Stack:
[    1.048712]  ffff880074027a90 ffffffff811f8513 0000000000000000 ffff880073e2df00
[    1.050842]  ffff880074bf3000 ffff880074027c94 ffff880074027b80 0000000000000000
[    1.052964]  ffff880074027ab0 ffffffff811f99d6 0000000000008041 0000000000000000
[    1.055090] Call Trace:
[    1.055891]  [<ffffffff811f8513>] do_dentry_open+0xb3/0x310
[    1.057059]  [<ffffffff811f99d6>] vfs_open+0x36/0x40
[    1.058163]  [<ffffffff81209766>] path_openat+0x1a6/0x13d0
[    1.059325]  [<ffffffff820239a3>] ? bunzip2+0x41f/0x41f
[    1.060449]  [<ffffffff8120ba2e>] do_filp_open+0x7e/0xe0
[    1.061582]  [<ffffffff8120ab66>] ? getname_flags+0x56/0x1f0
[    1.062771]  [<ffffffff811d87e5>] ? kmem_cache_alloc+0x1a5/0x200
[    1.063992]  [<ffffffff812196d6>] ? __alloc_fd+0x46/0x180
[    1.065143]  [<ffffffff811f9d16>] do_sys_open+0x116/0x1f0
[    1.066290]  [<ffffffff820239a3>] ? bunzip2+0x41f/0x41f
[    1.067419]  [<ffffffff811f9e0e>] SyS_open+0x1e/0x20
[    1.068524]  [<ffffffff81fdcc90>] do_name+0xc9/0x283
[    1.069630]  [<ffffffff81fdc0f7>] write_buffer+0x23/0x34
[    1.070775]  [<ffffffff81fdc133>] flush_buffer+0x2b/0x85
[    1.071917]  [<ffffffff81fdc108>] ? write_buffer+0x34/0x34
[    1.073069]  [<ffffffff82023c46>] __gunzip+0x299/0x341
[    1.074187]  [<ffffffff82023cee>] ? __gunzip+0x341/0x341
[    1.075320]  [<ffffffff82023cff>] gunzip+0x11/0x13
[    1.076399]  [<ffffffff81fdc059>] ? md_run_setup+0x9a/0x9a
[    1.077551]  [<ffffffff81fdc9af>] unpack_to_rootfs+0x171/0x275
[    1.078758]  [<ffffffff81fdc059>] ? md_run_setup+0x9a/0x9a
[    1.079914]  [<ffffffff81fdcab3>] ? unpack_to_rootfs+0x275/0x275
[    1.081133]  [<ffffffff81fdcb13>] populate_rootfs+0x60/0x114
[    1.082317]  [<ffffffff81002123>] do_one_initcall+0xb3/0x1d0
[    1.083506]  [<ffffffff81fdb11b>] kernel_init_freeable+0x192/0x21f
[    1.084766]  [<ffffffff818ee29e>] kernel_init+0xe/0x110
[    1.085903]  [<ffffffff818fb5c2>] ret_from_fork+0x22/0x40
[    1.087055]  [<ffffffff818ee290>] ? rest_init+0x90/0x90
[    1.088184] Code: df 7e b8 f0 ff ff ff e9 55 fe ff ff b8 f5 ff ff ff e9 4b fe ff ff 0f 1f 44 00 00 66 66 66 66 90 55 65 ff 05 0b 0f df 7e 48 89 e5 <48> 8b 47 28 65 ff 40 04 0f ae f0 8b 47 10 f6 c4 02 74 0a f3 90 
[    1.096625] RIP  [<ffffffff8121c450>] __mnt_want_write+0x10/0x70
[    1.097925]  RSP <ffff880074027a50>
[    1.098852] CR2: 0000000000000028
[    1.099757] ---[ end trace 83ea1c07e6cbf79c ]---
[    1.100818] Kernel panic - not syncing: Fatal exception


FYI, raw QEMU command line is:

	qemu-system-x86_64 -enable-kvm -cpu Penryn -kernel /pkg/linux/x86_64-rhel/gcc-4.9/58a94fa1824f21e2e94be7caad8673a95df89d58/vmlinuz-4.6.0-rc7-00001-g58a94fa -append 'root=/dev/ram0 user=lkp job=/lkp/scheduled/vm-vp-2G-1/bisect_boot-1-debian-x86_64-2015-02-07.cgz-x86_64-rhel-58a94fa1824f21e2e94be7caad8673a95df89d58-20160511-87678-16ow8qg-0.yaml ARCH=x86_64 kconfig=x86_64-rhel branch=linux-devel/devel-hourly-2016051109 commit=58a94fa1824f21e2e94be7caad8673a95df89d58 BOOT_IMAGE=/pkg/linux/x86_64-rhel/gcc-4.9/58a94fa1824f21e2e94be7caad8673a95df89d58/vmlinuz-4.6.0-rc7-00001-g58a94fa max_uptime=600 RESULT_ROOT=/result/boot/1/vm-vp-2G/debian-x86_64-2015-02-07.cgz/x86_64-rhel/gcc-4.9/58a94fa1824f21e2e94be7caad8673a95df89d58/0 LKP_SERVER=inn earlyprintk=ttyS0,115200 systemd.log_level=err debug apic=debug sysrq_always_enabled rcupdate.rcu_cpu_stall_timeout=100 panic=-1 softlockup_panic=1 nmi_watchdog=panic oops=panic load_ramdisk=2 prompt_ramdisk=0 console=ttyS0,115200 console=tty0 vga=normal rw ip=::::vm-vp-2G-1::dhcp'  -initrd /fs/sdd1/initrd-vm-vp-2G-1 -m 2048 -smp 4 -device e1000,netdev=net0 -netdev user,id=net0,hostfwd=tcp::23108-:22 -boot order=nc -no-reboot -watchdog i6300esb -rtc base=localtime -drive file=/fs/sdd1/disk0-vm-vp-2G-1,media=disk,if=virtio -drive file=/fs/sdd1/disk1-vm-vp-2G-1,media=disk,if=virtio -drive file=/fs/sdd1/disk2-vm-vp-2G-1,media=disk,if=virtio -drive file=/fs/sdd1/disk3-vm-vp-2G-1,media=disk,if=virtio -drive file=/fs/sdd1/disk4-vm-vp-2G-1,media=disk,if=virtio -drive file=/fs/sdd1/disk5-vm-vp-2G-1,media=disk,if=virtio -pidfile /dev/shm/kboot/pid-vm-vp-2G-1 -serial file:/dev/shm/kboot/serial-vm-vp-2G-1 -daemonize -display none -monitor null 





Thanks,
Xiaolong

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