【OLK 5.10】修复nbd异常参数告警问题

问题：
el0_svc_handler+0x190/0x260 arch/arm64/kernel/syscall.c:190
 el0_svc+0x10/0x218 arch/arm64/kernel/entry.S:1017
kobject_add_internal failed for 43:0 with -EEXIST, don't try to register things with the same name in the same directory.
------------[ cut here ]------------
WARNING: CPU: 0 PID: 239 at block/genhd.c:724 __device_add_disk+0xb98/0xdf8 block/genhd.c:724
Modules linked in:

问题分析：
nbd_genl_connect
    （获取index）
        nbd_dev_add（传入巨大负数index，check的时候进行左移比较，仍可正常创建，index值可能与已有的index重复）；

int first_minor = index << part_shift;

/*
	 * Too big index can cause duplicate creation of sysfs files/links,
	 * because MKDEV() expect that the max first minor is MINORMASK, or
	 * index << part_shift can overflow.
	 */
	if (first_minor < index || first_minor > MINORMASK)
		return -EINVAL;

当巨大的负值左移时，有可能将其左移成正数，可能与原index重复，导致异常

问题复现：
构造问题场景：
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index a35189098581..3773bcf83993 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1702,8 +1702,14 @@ static int nbd_dev_add(int index)
        struct gendisk *disk;
        struct request_queue *q;
        int err = -ENOMEM;
-       int first_minor = index << part_shift;
 
+       printk("%s index %d %d\n", __func__, index,  MINORMASK);
+       if (index == 1) {
+               index = -2147483648;
+       }
+
+       int first_minor = index << part_shift;
+       printk("first_minor %d\n", first_minor);
        /*
         * Too big index can cause duplicate creation of sysfs files/links,
         * because MKDEV() expect that the max first minor is MINORMASK, or
@@ -1854,6 +1860,7 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info)
                printk(KERN_ERR "nbd: must specify a size in bytes for the device\n");
                return -EINVAL;
        }
+

复现结果如下：

localhost login: [   28.306327] nbd_dev_add index 0 1048575
[   28.307030] first_minor 0
[   28.309128] nbd_dev_add index 1 1048575
[   28.309812] first_minor 0
[   28.310589] sysfs: cannot create duplicate filename '/devices/virtual/bdi/43:0'
[   28.311837] CPU: 25 PID: 1166 Comm: modprobe Not tainted 4.19.90-dirty #145
[   28.313010] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 04/01/2014
[   28.315252] Call Trace:
[   28.315699]  dump_stack+0xd4/0x10f
[   28.316284]  sysfs_warn_dup.cold+0x27/0x45
[   28.316982]  sysfs_create_dir_ns+0xec/0x110
[   28.317682]  kobject_add_internal+0x127/0x520
[   28.318422]  kobject_add_varg+0x39/0x50
[   28.319073]  kobject_add+0x60/0x90
[   28.319649]  ? mutex_lock+0x16/0x60
[   28.320240]  ? get_device_parent.isra.0+0x106/0x310
[   28.321070]  device_add+0x1ae/0xb10
[   28.321665]  bdi_register_va+0x10b/0x430
[   28.322329]  bdi_register+0x5b/0x80
[   28.322923]  ? vsnprintf+0x440/0x7d0
[   28.323520]  bdi_register_owner+0x34/0x80
[   28.324197]  __device_add_disk+0x52b/0x6a0
[   28.324900]  device_add_disk+0x17/0x20
[   28.325533]  nbd_dev_add+0x370/0x3cf [nbd]
[   28.326225]  ? 0xffffffffc0368000
[   28.326783]  nbd_init+0x18a/0x1000 [nbd]
[   28.327442]  do_one_initcall+0x7b/0x33f
[   28.328088]  ? gcov_event+0x70/0x676
[   28.328690]  do_init_module+0xa6/0x340
[   28.329328]  load_module+0x2132/0x24d0
[   28.329969]  ? __do_sys_finit_module+0x13a/0x190
[   28.330732]  __do_sys_finit_module+0x13a/0x190
[   28.331481]  __x64_sys_finit_module+0x1e/0x30
[   28.332215]  do_syscall_64+0xc1/0x250
[   28.332838]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[   28.333682] RIP: 0033:0x7f2fdedbc4e9
[   28.334279] Code: 00 f3 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 6f 39 2c 00 f7 d8 64 89 01 48
[   28.337318] RSP: 002b:00007fff2a5cac68 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
[   28.338576] RAX: ffffffffffffffda RBX: 00005563cf1473d0 RCX: 00007f2fdedbc4e9
[   28.339759] RDX: 0000000000000000 RSI: 00005563cee1bc26 RDI: 0000000000000003
[   28.340932] RBP: 00005563cee1bc26 R08: 0000000000000000 R09: 0000000000000000
[   28.342099] R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000000
[   28.343171] R13: 00005563cf147360 R14: 0000000000040000 R15: 00005563cf1473d0
[   28.344130] kobject_add_internal failed for 43:0 with -EEXIST, don't try to register things with the same name in the same directory.
[   28.345695] ------------[ cut here ]------------
[   28.346334] WARNING: CPU: 25 PID: 1166 at block/genhd.c:725 __device_add_disk.cold+0x40/0x150
[   28.347444] Modules linked in: nbd(+)
[   28.347941] CPU: 25 PID: 1166 Comm: modprobe Not tainted 4.19.90-dirty #145
[   28.348851] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 04/01/2014
[   28.350579] RIP: 0010:__device_add_disk.cold+0x40/0x150
[   28.351268] Code: ff 48 83 05 76 7b 8e 04 01 e9 95 ea ff ff 48 c7 c7 90 2c be 9e 48 83 05 6a 6c 8e 04 01 e8 13 b2 7a ff 48 83 05 65 6c 8e 04 01 <0f> 0b 48 83 05 63 6c 8e 04 01 48 83 05 63 6c 8e 04 01 e9 29 ed ff
[   28.353701] RSP: 0018:ffffc900084e7c28 EFLAGS: 00010202
[   28.354388] RAX: 0000000000000024 RBX: 0000000000000000 RCX: 0000000000000000
[   28.355323] RDX: 0000000000000000 RSI: ffff88900f255bf8 RDI: ffff88900f255bf8
[   28.356253] RBP: ffff88810845c000 R08: ffff88900f255bf8 R09: 0000000000000005
[   28.357186] R10: 00000000000003df R11: ffffffff9feb6f4d R12: 0000000000000001
[   28.358117] R13: ffff88810845c00c R14: 0000000000000000 R15: ffff88810845c070
[   28.359050] FS:  00007f2fdf8e9040(0000) GS:ffff88900f240000(0000) knlGS:0000000000000000
[   28.360103] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   28.360857] CR2: 00007f2fdee32395 CR3: 0000000123954000 CR4: 00000000000006e0
[   28.361796] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   28.362721] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   28.363648] Call Trace:
[   28.363978]  device_add_disk+0x17/0x20
[   28.364472]  nbd_dev_add+0x370/0x3cf [nbd]
[   28.365014]  ? 0xffffffffc0368000
[   28.365450]  nbd_init+0x18a/0x1000 [nbd]
[   28.365975]  do_one_initcall+0x7b/0x33f
[   28.366475]  ? gcov_event+0x70/0x676
[   28.366954]  do_init_module+0xa6/0x340
[   28.367443]  load_module+0x2132/0x24d0
[   28.367944]  ? __do_sys_finit_module+0x13a/0x190
[   28.368542]  __do_sys_finit_module+0x13a/0x190
[   28.369123]  __x64_sys_finit_module+0x1e/0x30
[   28.369694]  do_syscall_64+0xc1/0x250
[   28.370178]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[   28.370838] RIP: 0033:0x7f2fdedbc4e9
[   28.371307] Code: 00 f3 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 6f 39 2c 00 f7 d8 64 89 01 48
[   28.373705] RSP: 002b:00007fff2a5cac68 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
[   28.374680] RAX: ffffffffffffffda RBX: 00005563cf1473d0 RCX: 00007f2fdedbc4e9
[   28.375593] RDX: 0000000000000000 RSI: 00005563cee1bc26 RDI: 0000000000000003
[   28.376493] RBP: 00005563cee1bc26 R08: 0000000000000000 R09: 0000000000000000
[   28.377395] R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000000
[   28.378297] R13: 00005563cf147360 R14: 0000000000040000 R15: 00005563cf1473d0
[   28.379202] ---[ end trace c19b64e7262f65ca ]---
[   28.379837] sysfs: cannot create duplicate filename '/dev/block/43:0'
[   28.380673] CPU: 25 PID: 1166 Comm: modprobe Tainted: G        W         4.19.90-dirty #145
[   28.381744] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 04/01/2014
[   28.383421] Call Trace:
[   28.383750]  dump_stack+0xd4/0x10f
[   28.384193]  sysfs_warn_dup.cold+0x27/0x45
[   28.384722]  sysfs_do_create_link_sd.isra.0+0x107/0x120
[   28.385400]  sysfs_create_link+0x29/0x60
[   28.385910]  device_add+0xa87/0xb10
[   28.386362]  __device_add_disk+0x1fe/0x6a0
[   28.386895]  device_add_disk+0x17/0x20
[   28.387381]  nbd_dev_add+0x370/0x3cf [nbd]
[   28.387918]  ? 0xffffffffc0368000
[   28.388350]  nbd_init+0x18a/0x1000 [nbd]
[   28.388860]  do_one_initcall+0x7b/0x33f
[   28.389353]  ? gcov_event+0x70/0x676
[   28.389821]  do_init_module+0xa6/0x340
[   28.390309]  load_module+0x2132/0x24d0
[   28.390798]  ? __do_sys_finit_module+0x13a/0x190
[   28.391394]  __do_sys_finit_module+0x13a/0x190
[   28.391969]  __x64_sys_finit_module+0x1e/0x30
[   28.392529]  do_syscall_64+0xc1/0x250
[   28.393015]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[   28.393660] RIP: 0033:0x7f2fdedbc4e9
[   28.394122] Code: 00 f3 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 6f 39 2c 00 f7 d8 64 89 01 48
[   28.396488] RSP: 002b:00007fff2a5cac68 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
[   28.397451] RAX: ffffffffffffffda RBX: 00005563cf1473d0 RCX: 00007f2fdedbc4e9
[   28.398366] RDX: 0000000000000000 RSI: 00005563cee1bc26 RDI: 0000000000000003
[   28.399277] RBP: 00005563cee1bc26 R08: 0000000000000000 R09: 0000000000000000
[   28.400193] R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000000
[   28.401107] R13: 00005563cf147360 R14: 0000000000040000 R15: 00005563cf1473d0
[   28.402056] ------------[ cut here ]------------
[   28.402662] WARNING: CPU: 25 PID: 1166 at fs/sysfs/group.c:115 internal_create_group+0x348/0x660
[   28.403796] Modules linked in: nbd(+)
[   28.404277] CPU: 25 PID: 1166 Comm: modprobe Tainted: G        W         4.19.90-dirty #145
[   28.405353] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 04/01/2014
[   28.407056] RIP: 0010:internal_create_group+0x348/0x660
[   28.407731] Code: 04 01 89 e8 eb 8f 48 83 05 b4 f9 c0 04 01 48 c7 c7 90 2c be 9e 48 83 05 c5 f9

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