loop: fix NULL dereference if mount fails
Commit
bb21488482bd36eae6b30b014d93619063773fd4 ("[PATCH] switch loop")
started to pass NULL bdev to ioctl hook.
Steps to reproduce:
[boot with loop.max_part=1]
[mount -o loop something so mount fails]
BUG: unable to handle kernel NULL pointer dereference at
00000000000000b8
IP: [<
ffffffff811486ee>] blkdev_ioctl+0x2e/0xa30
PGD 0
Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
last sysfs file: /sys/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:35/ACPI0003:00/power_supply/ACAD/online
CPU 0
Modules linked in: zfs nvidia(P) [last unloaded: zfs]
Pid: 15177, comm: mount Tainted: P 2.6.32-rc4-zfs #2 Satellite X200
RIP: 0010:[<
ffffffff811486ee>] [<
ffffffff811486ee>] blkdev_ioctl+0x2e/0xa30
RSP: 0018:
ffff88003b3d5bb8 EFLAGS:
00010286
RAX:
0000000000000000 RBX:
0000000000000000 RCX:
0000000000000000
RDX:
000000000000125f RSI:
0000000000000000 RDI:
0000000000000000
RBP:
ffff88003b3d5ce8 R08:
0000000000000000 R09:
0000000000000000
R10:
0000000000000000 R11:
0000000000000000 R12:
00007ffffffff000
R13:
0000000000000000 R14:
ffff880071cef280 R15:
00000000000200da
FS:
00007fd77cfe7740(0000) GS:
ffff880001600000(0000) knlGS:
0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0:
000000008005003b
CR2:
00000000000000b8 CR3:
0000000001001000 CR4:
00000000000026f0
DR0:
0000000000000000 DR1:
0000000000000000 DR2:
0000000000000000
DR3:
0000000000000000 DR6:
00000000ffff0ff0 DR7:
0000000000000400
Process mount (pid: 15177, threadinfo
ffff88003b3d4000, task
ffff88007572f920)
Stack:
ffff88003b3d5c38 ffffffff812f95f5 ffff88007eeb6600 0000000000000000
<0>
0000000000000000 ffff88003b3d5c18 ffffffff811547d9 ffff88001bf11ef0
<0>
7fffffffffffffff ffff88001bf11ee8 ffff88001bf11ef0 0000000000000000
Call Trace:
[<
ffffffff812f95f5>] ? schedule_timeout+0x1f5/0x250
[<
ffffffff811547d9>] ? rb_insert_color+0x109/0x140
[<
ffffffff812fb754>] ? _spin_unlock_irq+0x14/0x40
[<
ffffffff812f84c6>] ? wait_for_common+0x66/0x170
[<
ffffffff8105a280>] ? default_wake_function+0x0/0x10
[<
ffffffff810f8258>] ioctl_by_bdev+0x38/0x50
[<
ffffffff811d2481>] loop_clr_fd+0x1e1/0x210
[<
ffffffff811d2522>] lo_release+0x72/0x80
[<
ffffffff810f934c>] __blkdev_put+0x1ac/0x1d0
[<
ffffffff810f937b>] blkdev_put+0xb/0x10
[<
ffffffff810f93b9>] blkdev_close+0x39/0x60
[<
ffffffff810ccef3>] __fput+0xd3/0x230
[<
ffffffff810cd06d>] fput+0x1d/0x30
[<
ffffffff810c9680>] filp_close+0x50/0x80
[<
ffffffff81061f11>] put_files_struct+0x81/0x100
[<
ffffffff81061fde>] exit_files+0x4e/0x60
[<
ffffffff81063ec5>] do_exit+0x6b5/0x730
[<
ffffffff8107b279>] ? up_read+0x9/0x10
[<
ffffffff8104c86e>] ? do_page_fault+0x18e/0x2a0
[<
ffffffff81063f81>] do_group_exit+0x41/0xc0
[<
ffffffff81064012>] sys_exit_group+0x12/0x20
[<
ffffffff81030deb>] system_call_fastpath+0x16/0x1b
Code: f8 48 89 e5 48 81 ec 30 01 00 00 48 89 5d d8 4c 89 6d e8 4c 89 65 e0 4c 89 75 f0 4c 89 7d f8 48 89 bd e8 fe ff ff 49 89 cd 89 f3 <49> 8b 88 b8 00 00 00 81 fa 68 12 00 00 0f 84 57 05 00 00 0f 86
RIP [<
ffffffff811486ee>] blkdev_ioctl+0x2e/0xa30
RSP <
ffff88003b3d5bb8>
CR2:
00000000000000b8
---[ end trace
c0b4d3c3118d1427 ]---
Fixing recursive fault but reboot is needed!
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>