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SubjectRe: [PATCH V4] brd: check and limit max_part par
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On 2/3/20 9:53 AM, Zhiqiang Liu wrote:
> Friendly ping...
>
> On 2020/1/21 12:04, Zhiqiang Liu wrote:
>>
>> In brd_init func, rd_nr num of brd_device are firstly allocated
>> and add in brd_devices, then brd_devices are traversed to add each
>> brd_device by calling add_disk func. When allocating brd_device,
>> the disk->first_minor is set to i * max_part, if rd_nr * max_part
>> is larger than MINORMASK, two different brd_device may have the same
>> devt, then only one of them can be successfully added.
>> when rmmod brd.ko, it will cause oops when calling brd_exit.
>>
>> Follow those steps:
>> # modprobe brd rd_nr=3 rd_size=102400 max_part=1048576
>> # rmmod brd
>> then, the oops will appear.
>>
>> Oops log:
>> [ 726.613722] Call trace:
>> [ 726.614175] kernfs_find_ns+0x24/0x130
>> [ 726.614852] kernfs_find_and_get_ns+0x44/0x68
>> [ 726.615749] sysfs_remove_group+0x38/0xb0
>> [ 726.616520] blk_trace_remove_sysfs+0x1c/0x28
>> [ 726.617320] blk_unregister_queue+0x98/0x100
>> [ 726.618105] del_gendisk+0x144/0x2b8
>> [ 726.618759] brd_exit+0x68/0x560 [brd]
>> [ 726.619501] __arm64_sys_delete_module+0x19c/0x2a0
>> [ 726.620384] el0_svc_common+0x78/0x130
>> [ 726.621057] el0_svc_handler+0x38/0x78
>> [ 726.621738] el0_svc+0x8/0xc
>> [ 726.622259] Code: aa0203f6 aa0103f7 aa1e03e0 d503201f (7940e260)
>>
>> Here, we add brd_check_and_reset_par func to check and limit max_part par.
>>
>> --
>> V3->V4:(suggested by Ming Lei)
>> - remove useless change
>> - add one limit of max_part
>>
>> V2->V3: (suggested by Ming Lei)
>> - clear .minors when running out of consecutive minor space in brd_alloc
>> - remove limit of rd_nr
>>
>> V1->V2: add more checks in brd_check_par_valid as suggested by Ming Lei.
>>
>> Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
>> ---
>> drivers/block/brd.c | 27 +++++++++++++++++++++++----
>> 1 file changed, 23 insertions(+), 4 deletions(-)
>>

Looks good to me.
Reviewed-by: Bob Liu <bob.liu@oracle.com>

>> diff --git a/drivers/block/brd.c b/drivers/block/brd.c
>> index df8103dd40ac..4684f95e3369 100644
>> --- a/drivers/block/brd.c
>> +++ b/drivers/block/brd.c
>> @@ -389,11 +389,12 @@ static struct brd_device *brd_alloc(int i)
>> * is harmless)
>> */
>> blk_queue_physical_block_size(brd->brd_queue, PAGE_SIZE);
>> - disk = brd->brd_disk = alloc_disk(max_part);
>> + disk = brd->brd_disk = alloc_disk(((i * max_part) & ~MINORMASK) ?
>> + 0 : max_part);
>> if (!disk)
>> goto out_free_queue;
>> disk->major = RAMDISK_MAJOR;
>> - disk->first_minor = i * max_part;
>> + disk->first_minor = i * disk->minors;
>> disk->fops = &brd_fops;
>> disk->private_data = brd;
>> disk->queue = brd->brd_queue;
>> @@ -468,6 +469,25 @@ static struct kobject *brd_probe(dev_t dev, int *part, void *data)
>> return kobj;
>> }
>>
>> +static inline void brd_check_and_reset_par(void)
>> +{
>> + if (unlikely(!max_part))
>> + max_part = 1;
>> +
>> + if (max_part > DISK_MAX_PARTS) {
>> + pr_info("brd: max_part can't be larger than %d, reset max_part = %d.\n",
>> + DISK_MAX_PARTS, DISK_MAX_PARTS);
>> + max_part = DISK_MAX_PARTS;
>> + }
>> +
>> + /*
>> + * make sure 'max_part' can be divided exactly by (1U << MINORBITS),
>> + * otherwise, it is possiable to get same dev_t when adding partitions.
>> + */
>> + if ((1U << MINORBITS) % max_part != 0)
>> + max_part = 1UL << fls(max_part);
>> +}
>> +
>> static int __init brd_init(void)
>> {
>> struct brd_device *brd, *next;
>> @@ -491,8 +511,7 @@ static int __init brd_init(void)
>> if (register_blkdev(RAMDISK_MAJOR, "ramdisk"))
>> return -EIO;
>>
>> - if (unlikely(!max_part))
>> - max_part = 1;
>> + brd_check_and_reset_par();
>>
>> for (i = 0; i < rd_nr; i++) {
>> brd = brd_alloc(i);
>>
>

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