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Subject[100/146] loop: limit max_part module param to DISK_MAX_PARTS
2.6.38-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Namhyung Kim <namhyung@gmail.com>

commit 78f4bb367fd147a0e7e3998ba6e47109999d8814 upstream.

The 'max_part' parameter controls the number of maximum partition
a loop block device can have. However if a user specifies very
large value it would exceed the limitation of device minor number
and can cause a kernel panic (or, at least, produce invalid
device nodes in some cases).

On my desktop system, following command kills the kernel. On qemu,
it triggers similar oops but the kernel was alive:

$ sudo modprobe loop max_part0000
------------[ cut here ]------------
kernel BUG at /media/Linux_Data/project/linux/fs/sysfs/group.c:65!
invalid opcode: 0000 [#1] SMP
last sysfs file:
CPU 0
Modules linked in: loop(+)

Pid: 43, comm: insmod Tainted: G W 2.6.39-qemu+ #155 Bochs Bochs
RIP: 0010:[<ffffffff8113ce61>] [<ffffffff8113ce61>] internal_create_group=
+0x2a/0x170
RSP: 0018:ffff880007b3fde8 EFLAGS: 00000246
RAX: 00000000ffffffef RBX: ffff880007b3d878 RCX: 00000000000007b4
RDX: ffffffff8152da50 RSI: 0000000000000000 RDI: ffff880007b3d878
RBP: ffff880007b3fe38 R08: ffff880007b3fde8 R09: 0000000000000000
R10: ffff88000783b4a8 R11: ffff880007b3d878 R12: ffffffff8152da50
R13: ffff880007b3d868 R14: 0000000000000000 R15: ffff880007b3d800
FS: 0000000002137880(0063) GS:ffff880007c00000(0000) knlGS:00000000000000=
00
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000422680 CR3: 0000000007b50000 CR4: 00000000000006b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 0000000000000000 DR7: 0000000000000000
Process insmod (pid: 43, threadinfo ffff880007b3e000, task ffff880007afb9c=
0)
Stack:
ffff880007b3fe58 ffffffff811e66dd ffff880007b3fe58 ffffffff811e570b
0000000000000010 ffff880007b3d800 ffff880007a7b390 ffff880007b3d868
0000000000400920 ffff880007b3d800 ffff880007b3fe48 ffffffff8113cfc8
Call Trace:
[<ffffffff811e66dd>] ? device_add+0x4bc/0x5af
[<ffffffff811e570b>] ? dev_set_name+0x3c/0x3e
[<ffffffff8113cfc8>] sysfs_create_group+0xe/0x12
[<ffffffff810b420e>] blk_trace_init_sysfs+0x14/0x16
[<ffffffff8116a090>] blk_register_queue+0x47/0xf7
[<ffffffff8116f527>] add_disk+0xdf/0x290
[<ffffffffa00060eb>] loop_init+0xeb/0x1b8 [loop]
[<ffffffffa0006000>] ? 0xffffffffa0005fff
[<ffffffff8100020a>] do_one_initcall+0x7a/0x12e
[<ffffffff81096804>] sys_init_module+0x9c/0x1e0
[<ffffffff813329bb>] system_call_fastpath+0x16/0x1b
Code: c3 55 48 89 e5 41 57 41 56 41 89 f6 41 55 41 54 49 89 d4 53 48 89 fb=
48 83 ec 28 48 85 ff 74 0b 85 f6 75 0b 48 83 7f 30 00 75 14 <0f> 0b eb fe =
48 83 7f 30 00 b9 ea ff ff ff 0f 84 18 01 00 00 49
RIP [<ffffffff8113ce61>] internal_create_group+0x2a/0x170
RSP <ffff880007b3fde8>
---[ end trace a123eb592043acad ]---

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Cc: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/block/loop.c | 3 +++
1 file changed, 3 insertions(+)

--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1707,6 +1707,9 @@ static int __init loop_init(void)
if (max_part > 0)
part_shift = fls(max_part);

+ if ((1UL << part_shift) > DISK_MAX_PARTS)
+ return -EINVAL;
+
if (max_loop > 1UL << (MINORBITS - part_shift))
return -EINVAL;




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